Synthroid vs Levothyroxine: When to Switch Thyroid Medications

Synthroid vs Levothyroxine: When to Switch Thyroid Medications

Even though Synthroid and Levothyroxine contain the same active ingredient, they may not be tolerated equally among all patients.

This means that certain patients do better on one medication compared to the other!

Learn how to identify if you are taking the right type of medication and when to consider switching in this post:

Generic Levothyroxine vs Brand name Synthroid

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The most common medication used to treat hypothyroidism is Levothyroxine.

Levothyroxine is considered a “generic” version of the thyroid medication Synthroid.

But is there a difference and does it actually matter?

The answer is yes, there may actually be a difference despite these medications being almost exactly the same.

Generic medications are usually created after a brand-name medication goes off-patent.

Other pharmaceutical companies can then come in and make a “me too” version of the medication and they often sell it for cheaper than the original.

In this case, we have Levothyroxine which is the generic, and Synthroid which is the brand name medication.

But despite both of these medications having the exact same ACTIVE ingredient (thyroxine) (1), they are not the EXACT same.

And even though the difference is not big, it may actually matter to certain people (especially those who are sensitive).

The active thyroid hormone and the active ingredient in both medications is the thyroid hormone Thyroxine.

Thyroxine is the bio-identical pharmaceutical version of the T4 thyroid hormone that your body produces naturally.

Both Synthroid and Levothyroxine contain this active ingredient.

So we know that the difference between these medications probably has little to do with the active ingredient and more to do with the inactive ingredients.

Inactive ingredients are known as fillers, dyes, and binders which help hold the active medication in place.

All pharmaceutical medications have inactive ingredients and these ingredients can help delay the absorption of medications, protect the ingredients from damage in the intestinal tract, and so on.

The problem is that some of these medications contain ingredients that may actually cause negative symptoms and reactions in certain sensitive patients (2).

It is this small difference that may account for the difference in bioequivalence seen between generic and brand-name levothyroxine in some studies (3). 

This study showed that using Synthroid resulted in a more rapid rise in total serum triiodothyronine and a higher peak serum T3 when compared to other T4-only products.

And even though this result didn’t reach statistical significance, it may still be important for certain people.

Remember that T3 is the most active and potent form of thyroid hormone in your body (4).

So even small changes to T3 may have a big impact on certain individuals.

It may be small differences such as this that result in improvement when switching from one medication to the other, even though technically they are the “same thing”.

And this isn’t the only study to show a difference between these medications.

Another study, which evaluated children with hypothyroidism, showed that Synthroid resulted in a significantly lower TSH when compared to generic LT4 medication replacement therapy (5).

What is interesting is that the people who seemed to be sensitive to the difference were only patients with certain types of hypothyroidism (congenital hypothyroidism in this case).

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What this tells us is that not all patients are equally responsive to all types of thyroid medications (which shouldn’t come as a surprise).

This is a potentially big issue because most physicians, when prescribing medications, often recommend cheaper generic alternatives to name-brand medications.

To further complicate this, some pharmacists can even alter medications given to patients for insurance and cost purposes.

While this may be a strategy for saving money it may not be the best strategy when it comes to the symptomatic management of patients with hypothyroidism!


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The Complete List of Thyroid Lab tests:

The list includes optimal ranges, normal ranges, and the complete list of tests you need to diagnose and manage thyroid disease correctly!


When to Consider Switching Thyroid Medications

Does this mean that you need to run out and try to change your thyroid medication from Synthroid to Levothyroxine or vice versa?

Not necessarily, but it never hurts to be informed and educated on the topic.

Instead of jumping to changing your medication, it may be a good idea to sit down and evaluate your current situation.

If, for instance, you are currently taking Levothyroxine and you are having trouble with hypothyroid symptoms (such as fatigue, weight gain, cold intolerance, and so on) then it may be worth considering altering your medication.

There are also other conditions that may cause you to consider altering your medication and I’ve included a list below:

  • #1. If you are simply not responding to your current medication
  • #2. If you have a “normal” TSH but still remain symptomatic
  • #3. If you suspect absorption issues
  • #4. If you suspect a reaction to inactive fillers/binders
  • #5. If cost is a potential issue for you
  • #6. If you have congenital hypothyroidism or if you have had your thyroid removed or destroyed with radioactive iodine

If you fall into any of these categories then you may want to consider changing from whichever medication you are currently taking to the other.

So if you fit the criteria on the list and you are taking 100mcg of Levothyroxine then you would want to switch to 100mcg of Synthroid.

You would then want to make sure that you check your thyroid lab tests after about 6 weeks to ensure that you did well with the transition.

Most physicians should not give you any trouble in making this type of switch, but they may give you trouble if you asked to be switched from Synthroid to another medication like Armour thyroid.

Cost Difference Between Synthroid & Levothyroxine, Tirosint & Levoxyl

Another factor to consider is the cost of the various forms of T4 medications.

Unfortunately, the cheapest medications tend to be Synthroid and Levothyroxine. 

The more expensive medications (which may be necessary for some people) tend to be upwards of $30 per month all the way up to $130 per month in the case of Tirosint. 

You can see a comparison chart below: 

It’s important to remember that the cost of medications often depends on which pharmacy you go to. 

Some pharmacies are just inherently more expensive than other pharmacies, even for the same medication. 

Also, in some cases, it may be cheaper to pay the “cash price” for medications instead of your insurance co-pay. 

Below you will find the average cost of a 30-day supply of 100mcg of each of the Thyroxine medications. 

The average cost of Levothyroxine & Synthroid 30-day supply:

Synthroid and Levothyroxine tend to be the same price, but often your insurance may cover one and not the other. 

If you fall into this category then you can usually pay the “cash price” and still pay the same total price. 

The average cost of Tirosint 30-day supply:

Tirosint is the most expensive T4-only thyroid medication coming in at around $130 per month for the 100mcg dose. 

Even though Tirosint is more expensive than other medications there are some coupon options that you can use to help reduce the cost. 

The average cost of Levoxyl 30-day supply:

Levoxyl is another T4-only thyroid medication that is slightly more expensive when compared to Levothyroxine but cheaper than Tirosint. 

Each of these thyroid medications falls into the class of “Thyroxines” which means they all contain T4. 

Even though they all contain the same medication, you may find that you do better on one versus the other. 

Because of this, you may need to “play around” with which medication you are using. 

What to do if Synthroid & Levothyroxine Aren’t Working

In some situations, you may find that switching from Synthroid to Levothyroxine (or vice versa) still doesn’t help remove all of your symptoms.

What are you supposed to do if you fall into this situation?

The first is to not lose hope or faith!

You still have many options worth considering.

I’ve created a list of the next steps you’ll want to consider if you fall into this category:

  • #1. Try the 50mcg Tablet of Levothyroxine/Synthroid – The 50mcg tablet has the fewest amount of inactive binders and fillers compared to other dosages. If you are taking 100mcg of Synthroid you may find benefit in taking 2, 50mcg tablets instead of 1, 100mcg tablet.
  • #2. Consider switching from Levothyroxine/Synthroid to TirosintTirosint is a cleaner thyroid medication with only 4 ingredients (3 of which are inactive ingredients). This should be compared to Levothyroxine/Synthroid which contains 10+ inactive ingredients.
  • #3. Consider altering the time of day that you take your medication – Some individuals may find significant improvement in taking their medication in the evening compared to the morning. Some studies show people who take thyroid medication at night (6) have higher free thyroid hormone concentration in the serum.
  • #4. Consider looking into medications that contain T3 (triiodothyronine) such as NDT (Armour Thyroid, WP thyroid, and Nature-Throid) – These medications may be preferred in individuals who have thyroid conversion issues and in those who still remain symptomatic despite normal thyroid lab tests.

What is the Difference Between Synthroid/Levothyroxine & Liothyronine?

Synthroid and Levothyroxine are both considered T4-only thyroid medications which means that they contain the bio-identical thyroid hormone Thyroxine.

Liothyronine, on the other hand, contains the most potent thyroid hormone which is known as T3 or triiodothyronine.

T3 is about 3-4 times more powerful than T4 (depending on which study you look at).

T3 is available in two medications: Liothyronine (generic) and Cytomel (brand name).

Many physicians and Doctors are hesitant to prescribe T3 due to the relatively short half-life of T3 when compared to T4.

In addition, because T3 is more potent than T4, patients who use T3 tend to have more side effects.

But these are not reasons to completely avoid this medication!

Liothyronine may be a superior medication when it comes to weight loss and may be necessary for certain individuals.

You can learn more about T3 in this post.

Final Thoughts

The bottom line?

There is a potential difference between Levothyroxine and Synthroid but the difference is probably not noticeable for most people.

If you are currently taking one or the other and you are doing well (meaning you are not symptomatic) then you probably don’t need to worry about changing up your medication regimen.

If, on the other hand, you are taking one and NOT experiencing relief in your symptoms then the information in this post may be especially relevant for you.

In this case, you may find relief in simply switching from the name brand to generic or vice versa.

Now I want to hear from you:

Are you currently taking Synthroid or Levothyroxine?

Are they working for you?

Are you still symptomatic despite normal thyroid lab tests?

Has switching medications helped you feel better?

Leave your comments below!







when to make the switch from levothyroxine to synthroid

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About Dr. Westin Childs

Hey! I'm Westin Childs D.O. (former Osteopathic Physician). I don't practice medicine anymore and instead specialize in helping people like YOU who have thyroid problems, hormone imbalances, and weight loss resistance. I love to write and share what I've learned over the years. I also happen to formulate the best supplements on the market (well, at least in my opinion!) and I'm proud to say that over 80,000+ people have used them over the last 7 years. You can read more about my own personal health journey and why I am so passionate about what I do.

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112 thoughts on “Synthroid vs Levothyroxine: When to Switch Thyroid Medications”

  1. At age 19 I was diagnosed with hyperthyroidism. I had my thyroid removed via radioactive iodine. I was unable to take the generic levothyroxine-so I’ve been on Synthroid ever since. I’m now 59. I had taken the same dose forever;.150mg. Over the last year, the Thyroid levels were low, then now too high then low again. I’m trying the generic for the first time, in obviously a long time. I’ve also been told that my Free T-3 is low. I’m now going to be trying your T3 Conversion booster. My Dr.(who is in NO way a natural remedy Dr. has recommended Potassium Iodide. I’m trying your product first.
    My eyes have been bothering me and I’ve experienced weight gain.

    • Hi Terri,

      That definitely seems like a reasonable approach! There is iodine in the T3 conversion booster, so you will be getting it either way. Good luck and keep us updated on your progress.

  2. I’ve been on Synthroid for 13 years. I started on it, insurance forced me to use the generic levothyroxine, and my hair began falling out. Lots of hair, not just a bit more. So I switched back to Synthroid. Now my new insurance co says it won’t pay for the non-generic and won’t take my doctor’s word for it. I’m at my wit’s end! How do I get the meds I need covered? Non-generic Synthroid is $45/month!

    • Hi Mini,

      Unfortunately, I don’t have any tips or tricks to help with the insurance side of things. Perhaps someone else reading this might know something?

      You might be able to try the cash price via which tends to be cheap with a coupon.

      • I was having issues with the generic and when switched to Synthroid there were amazing differences, I could even breathe easier!. Yes, the Synthroid is expensive, so what I asked my dr. to do was right the rx for 200 mcg (my actual dose is 100 mcg) and I use a tablet splitter to half it!

        • Hi Pat,

          Haha, that’s a good strategy! That’s actually what I do with my wife but we quadruple her dose so each month is worth 4 months (to build up a reserve).

          • Wow, I’m really loving this thread and getting some ideas, regarding how to get the most bang for my buck. Back in 82, when I was diagnosed with hypothyroidism Levothyroxine was prescribed. Although many of the symptoms dissipated, I began losing large amounts of hair. My doctor sent me to a dermatologist who actually told be I needed to collect all the hair and count each one to see if the hair I was loosing was enough to constitute an abnormal hair loss. I felt like the Dr. was telling me I didn’t know the difference between a NORMAL (small amount) of hair loss, which happens to everyone that washes their hair vs. an abnormal amount of hair loss, which I knew was the case. Exactly what is the thinking that brings any doctor to the conclusion that you want to pay $100.00 out-of-pocket just because you have nothing better to spend your money on? But, I digress. Eventually, due to other issues, I was prescribed Synthroid by a different doctor; however, not before I lost a significant enough amount of hair that I now almost always cover my head with either a hat, a wig. The latter is not really comfortable. At any rate, perhaps I would have lost my hair anyway as a result of having this disease, but since both my sister and mother also had the disease and lots of hair that they never lost, I wonder…The good news is that it appears to be under control at the moment. My question is, would a naturopathic physician be better suited in managing this, in addition to other, possibly hereditary, diseases going forward?

        • I have been having breathing issues and am on .50 levothyroxine. I have hashimotos disease and have nodules. I have been going to bed way too early @8:00 and mind is getting foggy again along with slight depression. I am turning 65 in April and work at an accounting firm and cannot have those symptoms during these busy times!! Maybe I will consider switching to Synthroid. A friend did and she has never felt more like her old self! Thanks for sharing. I thought I was crazy with the breathing issue!! Oh and I have also put on 25 pounds and at only 5 feet 1 inch not good!! 🙂

    • I have been using Synthroid for the last 18 years. Today I got my refill and I now paying 87.00 instead of the 30.00 in February. I cannot use the generic I did that and had to switch back to Synthroid. I feel your frustration and I am disgusted with the insurance company.

    • If your Doctor writes on the script, “Synthroid Only”, then Medicare/Medicade and most private Insurance Co.’s should cover a prescription of the brand name, Synthroid. I had the same problem up until just a few years ago when I learned this tip.

    • Hi there! I’m testing normal for my tsh when I’m not mediated but have a history of hypothyroidism,irregular cycles and miscarriages. My pregancies that I’ve carried to full term have always been when I’m on levothyroxine. I just started 25mcg of levothyroxine but no I can’t sleep and have terrible restless legs! Now I’m wondering if I’m hyperthyoid? What to do?

      • Hi Liz,

        The best thing to do would be to check your labs as they will let you know if you are using too much.

  3. I was taking 100mcg Synthroid then switched to generic for cost reasons and I have a rash on my face. Is this common or possible rash may be from something else? Ever hear of generic causing pimples/ break out? My skin for 62 years has never broke out unless I’ve had reaction to medications

    • I had irchy legs from ankle to knees because of some filler . I had to be firm with Walgreen’s to order it from a certain manufacturer that didn’t use that filler… It was a BP meds.

  4. Thank you for a clear description. For the past couple decades I have taken Synthroid. But I have a new doctor and she prescribed Levothyroxine. It cost one half what the Synthroid pills cost. I will begin taking it because I suspect it will not be significant difference for me since I suspect the other ingredients won’t effect me much. I really appreciate your taking time to explain. If there is a big difference, I will be sure to write about it here. I will also be on the lookout for reactions like the rash mentioned above.

  5. Hello Dr. Childs. At the end of July 2016 I had the radiation iodine for Grave’s disease. Since that time I have been taking Levothyroxine. After each 2 month blood test, my lab numbers are in the red. My dr has tried changing my dosages from 50mcg to 25 mcg, from taking 1 tablet 7 days a week in 50mcg and later told to cut the tabs in half and take 25mcg for 7 days per week.This is what the schedule has been since 07/2016:
    50mcg = 1 tablet each day (all taken before breakfast)
    After lab test – 50mcg = 1 tablet for 5 days per week
    After lab test – 50mcg = 1 tablet for 3 days per week
    After lab test – 25mcg = 1 tablet for 7 days per week
    After lab test – 25mcg = 1 tablet for 5 days per week
    After lab test – 25mcg = 1 tablet for 3 days per week
    After lab test – 25mcg = 1 tablet for 4 days per week
    And now, after this last test (06/2018)? She is prescribing 50mcg for 7 days a week (again), (this is what I originally started at in 2016).

    I feel like I am stuck in a loop. If my next labs are still out of balance after two years I think I may have to change doctors. What are your thoughts regarding the changes in Levothyroxine dosages and is it safe to cut the tablets in half and to skip days each week going from 7/wk to 5/wk to 3/wk and then up to 4/wk, etc?

    • Hi Cindy,

      Unfortunately, there is no way of knowing without the lab test values, reference ranges and so on. There isn’t enough information presented here for me to say.

  6. I have Hashimoto’s Disease and have been taking 100mcg of levothyroxine for many years. I switched insurance companies and now have been taking synthroid, the same dosage, for many months. I am now hyperthyroid again. Could it be the switch from generic to brand medication that is causing this?

    • Hi Ann,

      It’s possible but it may just be related to other factors as well such as a change in the demand for thyroid hormone in your body.

  7. I had a total thyroidectomy 3/28/18 and have been on 100mcg of Levothyroxine.

    I have been SO TIRED aka sleepy. This is not how I want to live the rest of my life!!! 57 years old I am.

    My Endocronoligist just prescribed me the brand name Synthroid, but said it won’t make a difference.

    “I need to see my PCD for my tiredness issue” per her.

    This started AFTER my thyroid was removed!

    Thank you for this informative article. If switching these 2 drugs doesn’t work, I guess I need to re-read your article &/or see a new Endocronoligist.

  8. Ok, I too switched to generic due to insurance reasons…
    This happened about 4 years ago and I remember side effects of fatigue and hair loss, etc. Now, it’s happened again and I wish insurance companies would understand there is a percentage this generic does not work for!! I had a battery of tests today after feeling dizzy and fatigue and I told my doctor I’m certain it is this switch.

    • Hi Lisa,

      If you can afford it you can pay the cash price for Synthroid which is usually around $20-30 per month. You don’t have to use whatever medication your insurance recommends and many drugs are insanely cheap with or without insurance. Most generic medications can be purchased for $4 with or without insurance.

  9. I was switched from synthroid to LEVOTHYROXINE without my knowledge. I have been on synthroid for five years and LEVOTHYROXINE for the past month. I have been so sick for the past month and couldn’t figure out why. I should note I had a major surgery April 30th and thought this maybe had something to do with my illness. I had an “ah ha” moment yesterday and checked my pill bottle label. My new doctor just prescribed me the LEVOTHYROXINE without asking or telling me of the change. I have Severe migraines, chills, sweating, chest pain, nausea, ear pain and more.

    • Hi Heather,

      Unfortunately, most physicians and pharmacists believe that the medications are interchangeable which leads to situations such as yours.

  10. Hello! I have been on levothyroxine 75mcg for about ten years now and have Hashimotos. Over the last year, my TSH has been fluctuating between low and high. This has caused symptoms of both hypo and hyper at times. My doctor just switched me to Levoxyl 75mcg. She said the dosage with the generic can be inconsistent and that Levoxyl is more stable. I’m sensitive to medication in general but I’m really hoping the medicine change doesn’t cause any side effects and I’m nervous about the change. I’ve had instances in the past where I’d miss my levothyroxine dose only by a few hours and would get anxiety, sweats etc. It was really odd. Here’s hoping Levoxyl doesn’t cause that. There shouldn’t be a “withdrawal” just by switching to the name brand right?

    • Hi Danny,

      The medications are not considered to be bioequivalent so you may experience symptoms when switching.

  11. Hi…Just DON’T STOP taking your thyroid med like I did. I felt like tearing my face off. Really strange, but was so frustrated. Took about a year to get better and now I’m on Synthroid.

  12. Interesting article, thank you. My Hashimoto’s experience has been a rough one. My levels were all within normal limits but my PCP was still suspecting thyroid problems due to my symptoms. He checked my thyroid peroxidase and it was high, almost 800. I went to an endocrinologist who titrated my Levothyroxine to 100mcg. It took awhile but I finally started feeling better. I feel my best when my TSH levels are on the hyperthyroid end of the scale. I switched insurance so had to switch doctors and also began down the infertility journey. The new doctor recommended the brand Synthroid, saying it is superior to the generic. Unfortunately my fatigue returned and my TSH levels went up 2 points. She then increased it to 112 mcg. It’s too early to tell, but I find 112 to be such an odd dose. I may ask her about switching to 2 50mcg per day after reading your article, so thank you. I’m also going to try taking it at night instead of first thing in the morning. Thanks again!

  13. Hi,
    I took L-Thyroxine Tabs 75mcg for 20 years with no problem.
    When I switched to Synthroid Tabs 75mcg a month ago and shortly after had difficulty controlling my Blood sugar ( I am on the Pod) and experienced episodes of rapid Heartbeat.
    Is there a correlation?

  14. Hi, I have lost my taste and smell after a total thyroidectomy May 2, 2018. Along with that I have another smell that permeates my being and goes along with eating a lot of different foods. I space out the timing of taking the Levoxyl from my other meds leaving about 6 or 7 hours between. I was first on Levothyroxine 175 mcg a day. now Levoxyl 175. I have cut the omeprazole in half keeping it the furthest away from the thyroid meds but nothing has changed. I have found tuna and seafood, onions, some fruit like strawberries as well as beef all evoke the bad taste and smell that is nauseating. I can get some salt taste and some sweet but that’s about all. I actually gained 5 lbs without hardly eating. The smell is in my nose and I feel like I smell like this smell. No smell with perfumes, etc. Got any ideas? would love to solve this problem! Thanks for your time!

  15. In January, 2018 I switched from Synthroid, same dosage for 22 years. I switched to the generic and about 5 weeks ago I started having pain in my arms and shoulder. I was also having fatigue and my doctor changed my dosage, after my test was low. After the change in dosage, my fatigue got better, but the pain is still in my arms. My primary doctor of many years would not change me the generic and she retired and my new doctor switched me to generic, because my new insurance price for synthroid was expensive. I see now why she did not want me to switch and I wish I had not switched. I may return to synthroid.

    • Hi Shirley,

      It’s unusual that switching makes a difference but it’s certainly true in a subgroup of people, you seem to be in that group!

  16. I am 55 years old and hypothyroidism runs in my family. I was prescribed Synthroid brand until the generic Levothyroxine became available (and insurance strongly pushed generics). My bloodwork results had always come back within tolerance until a few months after beginning the generics. My family doctor varied my generic dosage to dial in the test results, however, my reaction was wildly unpredictable. The test swung over and under the norm for over 2 months. Time to call in the highly-paid Endocrinologist. She had seen similar cases and immediately put me back on the Synthroid brand. My bloodwork came back to normal. My understanding of the issue is that the quality of generics is not monitored closely enough and some pharmacies mix the generic pills coming from the various manufacturers/batches (which increases the potential for volatility in the pills dispensed). I overpaid for useless generic prescriptions & doctors/specialists visits to “experiment” with generics. Lesson learned: Should have stayed on the brand name. I hope this story helps somebody get to the solution faster. DEMAND SYNTHROID BRAND NAME if the use of the generic drugs causes fluctuation in your blood test results.
    Money Savings Tip: The makers of Synthroid offer coupons on their website. It may reduce your insurance copay (worked for me).
    Full disclosure: I do not work for nor receive compensation from the pharmaceutical company.

  17. I’ve been on a generic thyroid drug for years now. Levoxyl and Levothyroxine (not sure when or why I switched from one to the other). My thyroid tests always show me in the normal range. However, I have been experiencing fatigue, super itchy skin, and weight gain over the last year (or so!) and my doctor is finally recommending a change, from Levothyroxine to the brand name Synthroid – same dose. Says I should notice a difference in about a week and if not, I guess we’ll come up with a different plan. I’m open to anything because the fatigue and itching are really driving me crazy. Very surprised this is needed after years of being on the same meds. The doctor has done every blood test under the sun but there doesn’t seem to be anything else wrong me with 🙂

  18. I have been taking 75 generic levothyroxine and have noticed I am lethargic. My recent test showed I was near 3 TSH which is .7 higher than last year. The doctor upped my dosage to 88 and switched me to Synthroid. I noticed immediately that my thyroid gland was kind of sensitive, where it felt more comfortable by putting some pressure on it with my hand at times. On the new medication my lethargy had subsided and I felt like doing stuff again, however wasn’t sure if I felt fully normal yet and my 2nd test after 6 weeks shows TSH over 5. I have improved but I can’t tell, is synthroid a problem and I should go back to generic Levothyroxine on a higher dose, or was the generic not working right all along and now synthroid is working but I need a still higher dose? not sure what I should think… waiting for Doctor to weigh in on this.

  19. I had my thyroid removed 10 yrs. ago. Cancer, but no treatment necessary. I have taken 112 mcg of levothyroxine only. Mylan was backordered and I have been given levoxyl and then another company’s levothyroxine. I’m having very hard side effects. Headache, shakes,an hour after taking it. I’ve asked for synthroid. I’ve had major surgery and I have lost 25 lbs. Can this affect the dose I should take? Seeing my doctor next week,but wouldn’t mind your opinion. Regards.

  20. I switched from Levothyroxine to synthroid a month and a half ago and since switching my vertigo has improved, I have lost 8 lbs, and I dont have so many aches and pains. I was currently on Levothyroxine for 8 years. I switched! I was told that the difference between the 2 drugs was the manufacturers. The levothyroxine supposedly is manufactured by several different companies and the synthroid is always made by the same manufacturer.

    • Hi Penny,

      Thanks for sharing and I’m glad you are feeling better! And you are correct in that multiple manufacturers are involved in producing levothyroxine.

  21. Hello
    Thank you so much for this information. It is very valuable. I got my thyroid removed in August 2018. I was put on Levothyroxine (75) to begin with. After 2 weeks my doc increased this to 100. I am having daily symptoms of tingling, numbness and burning (arms, face and legs). My TSH level was very high (40) so the Doctor increased my dose to 150 and it is now <5. Symptoms were still the same so I switched to Synthroid 2 weeks ago with no improvement. I am also taking calcitriol and calcium and with this my calcium levels are normal. Based on your experience what you think the issue could be, and what I might try next.

    Thank you so much, Bernie

  22. Hi,I’ve been on the generic brand (started at 50 now it’s 75)for a few years.Last blood test I had in April of this year came back normal yet I still suffer from fatigue,hair loss,dry skin,depression,cold intolerance-just to name a few!I recently seen my doctor and told her this but she didn’t mention anything about trying the brand name.I had another blood test done yesterday,so we shall see what that says!

  23. I had a nodule (benign) removed in August 2016, but since no part of my thyroid was removed, my levels looked OK. For years though I have experienced the symptoms of hypo….creeping weight gain or inability to lose weight, major fatigue, hair loss, etc. Doctor kept saying my labs looked ok. Finally, the endocrinologist started me on the generic at a dose of 50 and said I would feel better in about a week. At this time, my T4 was borderline low and he said it had been trending downwards over the years. The 3rd week on this medicine, I felt great…..felt like I actually lost a little weight and had more energy! The 4th week and thereafter (I’ve been on it a total of 9 weeks), I’ve experienced worse symptoms than when I began the medicine. Very rapid weight gain (almost 2 sizes in 5 weeks), horrible fatigue, dry hair that is falling out, dry skin, constipation, etc. Just did a round of labs. My T3 and T4 are now normal, but now my TSH was low. So, the doctor lowered my dose to 25 and switched me from the generic to the brand name, Synthroid. How soon should I notice a difference? Also, if symptoms are better does that mean my numbers should be ok? I just find it odd that I’ve suffered from the symptoms of hypo for so many years but my labs were always within range.

  24. Very useful article, thanks. I had half my thyroid gland removed due to hashimotos about 25 years ago. Have been on Levothyroxine since. About 4 years ago my symptoms started to get worse and since then life has been miserable. I’m hot/cold, no energy, can’t sleep, tingling in limbs etc, bloods are “normal”. Thinking about switching meds, so very helpful info.

    • Hi Audrey,

      Glad you found it helpful! Switching medications is certainly worth a shot, especially if you aren’t feeling well. Switching to a completely different medication such as Tirosint may also potentially be helpful.

  25. Which has more significant active ingredients? Synthroid name brand or Levothyroxine generic? I believe I’m allergic to acacia, lactose or corn starch (or a combination). My doctor switched me to Levothyroxine and I broke out in hives on my face and feel bloated. My low carb- healthy eating lifestyle results stalled. I would like to identify the drug with the least amount of additives.

  26. I unfortunately took a 30 day dose of levothyroxine which caused 40% necrosis of my liver. It led me to fulminate liver failure in 2 months. Where I had a full liver transplant at 30 yrs old. Which sparked the FDA recall recently. Tampa General Hospital said it was crazy how fast I went from the levothyroxine. Any attorneys working on the recall from China?

  27. I’m starting the brand name Synthroid tomorrow. I’m hoping the extreme fatigue, heat intolerance, dry skin, and dry hair subside. Oh yeah, the brain fog too. I was recently diagnosed with Hashimoto’s. TPO antibodies were 417. Was originally diagnosed with hypothyroidism in 2006. Have been consistently taking Levothyroxine since 2012. Was on 75 mcg and then was changed to 125mcg when my TSH got up to 11. I just want to feel better. It’s so frustrating trying to find a regimen to feel better.

    • Hi Barbara,

      It sounds as if your current set of symptoms may be related to hyperthyroidism which could be from your Hashimoto’s or from taking an excessively high dose of thyroid medication. You should have your labs tested to see where you sit.


    Hi, I have been on Levothyroxine for 10 years. We moved and I had to get a new doctor and bloodwork done. They put me on Synthroid and Armour Thyroid. On my third week…having a stiff neck and headache now itching on chest. I called the doctors office and they told me to not take any medication for one day then the next day I only take the Armour and not take Synthroid to see if that helps. How do I know if it’s the Synthroid or the Armour that’s causing this?

  29. I had thyroid cancer in 2000. I was on Synthroid 88mg& 25 Cytomel. Went to a new doctor switch to Armour 1.5. Starting losing weight and feeling better . My regular doctor didn’t like I switch to Armour. So she switched me back to Synthroid 125. I’m hoping that Synthroid makes me feel as good as I have been. Is there any problems with taking Armour, was told that the dose might not be the same every time. Just wondering which one I needed to be on. Thank you for your help.

  30. I was having shoulder and hip pain for a couple of years so my doctor suggested I take Synthroid instead of the generic brand I was taking and within no time I was pain free and have been ever since. I think of all the ibuprofen I took dealing with this chronic pain and it infuriates me. Hope this helps someone.

  31. Hi, I have been suffering from sever hair loss(I have lost about 2/3’s of my hair), being extremely cold, sensitivity to cold, dry brittle hair, dry skin to name a few things. My mom and both my sisters suffer from hypothyroidism and Hashimoto’s. My doctor checked my TSH and it was 2.7 due to it bring in the normal range he will not run any further test or check me for Hashimoto’s. I am wanting to know if you know of any doctor’s in Las Vegas that can help me to see if I have a thyroid issue or carry the Hashimoto’s gene?

  32. Hi, I had a total thyroidectomy 35 years ago due to cancer. I had been on levothyroxine, 75 mcg. for quite a few years. About 3 1/2 months ago I started taking a supplement that contained 100 mg. alpha-lipoic acid. My hair started falling out really bad. I’ve researched online and learned that this can happen and also to check with one’s Dr. before taking alpha-lipoic acid if one takes levothyroxine. I went to my Dr. around this time & TSH was very high, 10.550 and so my Levo dosage was increased to 100 mcg. and approx. 6 weeks later was tested again and TSH was low, .082 so my dosage of Levo was changed to 88 mcg. I did not tell my Dr. about taking the alpha-lipoic acid, but, of course, am no longer taking it. My worst concern is that my hair is still falling out badly. I’m taking 5,000 mcg. of biotin daily to try to remedy this and it is not helping yet. Can you connect the levothyroxine and alpha-lipoic acid problem and could I possibly do better on Synthroid? Other than supplementing with a hair, skin and nails supplement is there anything else I can do for my hair loss?

  33. Hello Dr. Childs: I had thyroid cancer 40 years ago and had a total thyroidectomy. For several years now I’ve been taking the levothyroxine 75 mcg. About 3 1/2 months ago I took a supplement that contained 100 mg. of alpha-lipoic acid. After over a month or so I noticed my hair was falling out more than it should. It was time for my routine checkup anyway so I went to my MD and my TSH levels were checked and TSH was high at 10.550 and T4 was normal at 1.33. At that time my MD increased my levothyroxine to 100 mcg. More than 5 weeks later I went back and was retested and my TSH was low at .082 and the T4 high at 2.20. At this time the Levo was decreased to 88 mcg. I had stopped the alpha-lipoic acid supplement because I had researched online and learned that I should have mentioned it to my Dr. since I was taking levothyroxine, and also that alpha-lipoic acid may cause hair loss. I would like to know what the connection between the two, Levo and alpha-lipoic acid is and what I can now do because my hair loss is still more than normal. I’m currently taking 5000 mcg. of biotin and a supplement for hair, skin, and nails. Also, I would like to know if perhaps I should switch to Synthroid.

  34. Hi Dr. Childs: I notice this morning that I have two comments on your website. I didn’t think the first one transmitted so I did another. Please feel free to delete the first one as the second one is more accurate. Very sorry for the inconvenience. I should have waited until the next day to confirm the transmit.

  35. Hi Dr. Childs,
    I’m a 55-year-old male, type 1 diabetic, and very active. I work out 4-5 days per week, ride mountain bikes, and dirt bikes.

    I found out that I have Hashimoto’s back in May 2019, after being fatigued and tired all of the time and bloated after eating, which included stomach cramps.

    My Endo put me on Levothyroxine, which seemed to help, especially after I removed gluten, soy, and most dairy. We needed to make some adjustments to get my TSH under 2 and in addition to that, I was able to talk the Endo into trying some T3, Liothyronine to try to get my T3 in a more optimal range.

    Things got better, but I still didn’t quite feel right, so we switched from Levothyroxine to Synthroid. That’s when I started to feel horrible. I wasn’t sure if I needed to let my body adjust, so I gave it 10 days. I felt so bad that I could barely function. I had to take time off the gym and rest. I could barely move. I felt like something was very wrong. My blood sugar has been effected big time with the lack of exercise, etc., and very hard to control.

    Have you ever heard of such a drastic change for the worse after switching from the generic, Levothyroxine to Synthroid? I wanted to hang in there and give it a chance, but I’m about ready to switch back.

    Any input would be greatly appreciated!

    Thank you.


  36. I have been hypothyroid since at least the early 1990s (I’m 71 now) and for 95 % of that time have taken Synthroid. For a short time several years ago, I was prescribed Levothyroxine, but it didn’t work out well for me. Went back to Synthroid. For the past maybe 10 yrs I have had two different dosages. 125 mcg on Monday, Wednesday and Friday. 137 on the other 4 days…fine. New doctor this early summer. I requested a thyroid med refill and received same dosages but in generic. After a month or so on it, I was experiencing constipation and then rectal bleeding from hemorrhoids. Then a couple of times I have had sudden vision issues. The PA called me Friday and said I have HYPERthyroid for the first time EVER! At the time I had forgotten until later that evening about the fact that I had been prescribed the generic and not my Synthroid. It all makes sense when looking at the time period of when the generic was started and the issues also began. I am now asking to be put back on my Synthroid to see if, in a month or so, any issues clear up. Does this make sense?

  37. Most people say they feel better after switching from generic to Synthroid but I tried it two times at .75mcg and .88mcg(usual dose) and by the 5th day I couldn’t function. Not sure what’s wrong with it but you shouldn’t have such dramatic symptoms like that just from switching brands. Would be great if there was stricter regulation on this stuff.

  38. After being diagnosed with hypothyroidism as a teenager, I was prescribed levothyroxine which wasn’t giving optimal results. My labs would come back within normal range but I was still symptomatic. For the past twenty years I have paid more in order to receive Synthroid which helped control symptoms better. The cost difference if frustrating! People are always surprised when I tell them there’s a difference in the two medications.

  39. I have been on immunotherapy for lung cancer for about 6 months. Due to the immunotherapy, my thyroid became lazy. Oncologist put me on Levothyroxine, after a few weeks of being on Levothyroxine my glucose shot up to 633, after several weeks of it increasing by a couple of 100 for about 5 treatments. I am now on oral diabetic medication & insulin. My family doctor wants to to take the Brand Synthroid to see if my glucose drops. (I have never been diabetic) Have you ever heard of this?

    • Hi Laura,

      It’s probably not the thyroid medication that caused your problem but more likely related to the same thing that caused your thyroid medication (probably your other therapies for lung cancer).

  40. Hi, I have a televisit with my PCP today to go over my thyroid labs from last week. I have been taking NP Thyroid (60mcg) once a day (before bed) and two on Thursday and Sunday. Previously I was on Synthroid, then Levothyroxine, then a combo of synthetic T3 and T4. Finally I was switched to Armour and when that wasn’t available, to NP Thyroid. I can never get my T3 (and sometimes T4) in range or they are at the bottom. We will see what labs say today. I just turned 65 and am now on Medicare and of course my Rx insurance doesn’t cover NP Thyroid or Armour or any generics, only synthetics. Don’t know if I should go back on levothyroxine, levo and liothyronine, or pay out of pocket for NP Thyroid. Frustrating.

    • Hi Kathy,

      Even if insurance doesn’t cover the medication you want the out of pocket cost usually isn’t too bad. So it’s often best for thyroid patients to pay for whatever is working (provided it IS working).

  41. Dr Childs.
    what is your input on taking thyroid medication first thing in the morning verses at night ? do you take it on an empty stomach or after eating? does it matter or have any affect on the effectiveness ? thank you.

  42. I am a 75 yo female. I went from an overactive thyroid to an under active thyroid about 12 years ago. I have been o 50 mcg levothyroxine since then. Recently my hair started falling out again along w chest pressure, heart palpitations and other symptoms and my doctor increased my dosage to 75 mcg. This helped a great deal however I am now having a reaction to the med. ie rash on back, nausea,pain in fingers and toes, mild headaches, pressure at base of my skull, dizziness and more. Doctor suggested talking to pharmacist about mfr. Pharm says same mfr. and talk to my dr. Should I request Synthroid? I had tried taking a pill and half of the 50 mcg for about a week and didn’t have this reaction.

  43. I have a prescription that I have been tacking for 8 years and on the bottle it states – Synthroid 175mcg, Levothroxine sod 175mcg.
    Am I getting synthroid or Levothroxine ?

  44. I had chemo for Hopkins lymphoma 25 years ago and went on 25 mcg of synthroid. About 7 years ago I was diagnosed with Lupus. My Rhumetologist said my levels needed to be adjusted and I’ve been on 175 mcg of levothyroxine for maybe 2 years.

    5 months ago I was hospitalized for a tear in my colon from diverticulitis. With the inability to eat substantially for a little while, I lost about 15 lbs going from 170 to about 155 (I’m 6’2″)! Since then, I’ve continues to lose weight, get night sweats, fevers, shortness of breath, swollen lymph nodes just to make a few. Never crossed my mind it may be a medication. I finally have an appointment with my Rhumetologist Monday, hopefully he’s got some good answers for me.

    • Hi Tam,

      I have a hard time understanding the mechanism by which levothyroxine can cause cancer when it’s the exact same hormone that the body produces naturally. How is it that taking the very same hormone the body produces all of the time can cause an increased risk of cancer when healthy people are producing it naturally each and every day? It’s more likely that there is just a broad increase risk of cancer across all people which is being picked up in this study and inappropriately attributed to levothyroxine use.

  45. I was on Synthroid 75 mcg for a long time and was now put on 50mcg and was given generic form. My hair has been thinning and falling out. I hope to get Synthroid on this prescription. Don’t want to go bald!

  46. Hi Dr. Childs: I was diagnosed with a pituitary tumor and an arachnoid cyst back in 1978 and had been on Bromocriptine until 2020. I had surgery at Weill Cornell then to remove the tumor and have been taking Levothyroxin 75 MCG every morning and Hydrocortisone 2 tables (10MG) in the morning and one at night.

    I have had a bad time until recently with severe fatigue, balance issues, vertigo. I also have had a weight gain that I cannot control and loss of hair, brittle nails, and very dry skin. I am very interested in your recommendation of perhaps switching to another synthroid. Joan Whalen

    • Hi Joan,

      I’m not able to provide medical advice but I have tons of information on this blog to help people learn more about their conditions!

  47. At 34 I found a lump in my neck and after surgery was diagnosed with thyroid cancer (so they removed the other half). I then had radioactive iodine treatment. There’s no family history of this problem. I was put on T3 liothyronine for about 5 months and then switched to T4 by the NHS endocrinologist. I’ve been having annual blood tests with him for the past 13 years, at first the T4 was ok but for the last 3 years he’s been seriously decreasing my dose I’m not on only 75mcg of T4 levo and I’m 2 stone heavier than I’ve ever been and started having digestive issues. I’ve changed my diet which has helped I’m getting a private doctor to check my bloods tomorrow but I HAVE to get this sorted. My weight and energy levels are troubling me. I won’t take no for answer and accept that I can’t have the quality of life I once had. I’m determined to make the change. I’ve given up alcohol and reduced sugar intake massively.

  48. Long story but will try and be short. Have been on levothyroxine for about 20 years but continued to have symptoms but the docs never suggested any change in meds since blood tests always looked fine. In mid January of this year I was just so fed up, I decided to stop taking it altogether. Eased myself off of them and went on a clean food diet, nothing processed and actually started feeling better, especially with my gut issues. But after about 2.5 months, early April, things started to go downhill. Was weak, swollen eyes, blurry vision, spaced out feeling and even slurred speech. I didn’t see my doc about any of this, but because I was getting worse, I decided to start back on the meds about 5 weeks ago. So things are somewhat better except now back to the horrid symptoms, was crying the first day back on them from a sadness that wasn’t situational, but was uncontrollable, also tired a lot, weak muscles and other symptoms not sure from hypothyroidism, low blood pressure, extreme sleepiness after eating, blurred eyesight after reading for short periods, and dizziness at times. So, basically I’m wondering if I should ask my doc to switch to a different med to see if results would be better. I obviously should change docs perhaps but don’t see that as an option until November of this year. I also think I’ve other issues that might be going on that are affecting my thyroid. Other organ issues perhaps. Since childhood (I’m 68) I’ve suffered from fainting spells that seemed to be from gut issues that come on every 5-6 years and no doc has figured out why. Had surgery when I was 10 years old but they couldn’t find anything to explain the episodes. I also suffered from an eating disorder for many many years and wonder if I’ve done some permanent damage to certain organs. I had my gallbladder removed about 12 years ago (though I think it was taken out because they couldn’t figure out what was really going on (was told afterwards that no stones were found) since I think it’s removal has not helped my gut issues). Anyway, sorry to go on, but after reading your article I’m thinking perhaps trying a different med might be beneficial. I’d prefer none, but perhaps that’s not an option. As the symptoms I continue to have now once again are heat/cold intolerance, deep depressive moments that are not situational but more of a gut feeling, low energy, and freezing cold hands always. I might add, I do get sufficient exercise and walk daily. I’m just tired of taking the meds but still having all the symptoms! Very frustrating to say the least. I feel like a lemon car. You know, things going wrong but the mechanics (docs) can never figure out what it is. Thank you so much for all of your informative articles on hypothyroidism.

  49. I have been on medically necessary synthroid since having my thyroid removed in 2015. I had 3 nodules and 3 cystic masses. I chose to have my thyroid removed after the 3rd cystic mass appeared with calcification. The biopsy came back negative. Removal and cross section revealed stage 1 cancer.
    I recently decided, through a pharmacy error, to try the levothyroxin. I took it for almost 3 months. The fatigue was terrible. I switched back and feel alot less symptomatic. Also, should I take a T3 supplement?

  50. I have been on generic levothyroxine for past 2 years but went to name brand synthroid 3 days ago and wow what a difference. Night sweats, heart rate and BP up. Feel very irritated. So no doubt there’s something to the change.

  51. This information is extremely valuable .Thank you! At age 5O I was diagnosed with Hypothyroidism and was prescribed Synthroid. I am now 80 years old . The pharmacist dispensed Levothyroxine at my last refill even though my doctors have indicated , Brand only. I know age brings on fatigue, and other nuisances , but this happened all too fast and I believe it is the change in the medication. As I have had reverse results with other medications, I suspect I am sensitive to this change . I have an apt.with my doctor in August. In the meantime can I approach the pharmacist and request a return to Synthroid. Thank you once more for this important article .

  52. Hi, because of being allergic to fillers and inactive ingrediances I took Tirosint and dont know why but had burning skin and upset stomack I thought it was free of allergens – should I try compounding – I dont know if Im allergic to microcrystalized cellulose that are added as a filler. Rita

  53. Hello Dr. Childs,
    I recently discovered that the generic brand of T3 (Liothyronine) contains mannitol, a sugar alcohol. My body does not tolerate any sugar alcohol well. It gives me g.i. upset, so I am going to switch to Cytomel!

    I just thought if you didn’t already have this information listed somewhere on your website, you may want to mention it.

    I also saw on the STTM website that Adthyza also contains mannitol. Folks who have trouble with sugar alcohols might want to stay away from these medications.

    Thanks for your extensive information! It’s a great resource!


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