How to Safely use Phentermine with Thyroid Problems

How to Safely use Phentermine with Thyroid Problems

So you have a thyroid problem and you’re looking for prescription medications that can help.

If so, chances are high that you will run across phentermine.

Phentermine is one of the most commonly prescribed medications used to help patients lose weight.

There’s one big problem though:

While it can be effective, it has the potential to cause certain problems for thyroid patients (those with hypothyroidism, Hashimoto’s, thyroidectomy, and RAI).

If these conditions are untreated and you take phentermine you may be putting unneeded stress on your adrenals and thyroid which can make you feel worse.

But, if you use this medication correctly, you can get the results you are looking for.

​It’s certainly not a miracle drug that will result in dramatic weight loss, but it can be helpful for a variety of reasons and is still worth considering in certain situations.

With that in mind, let’s talk about how to use phentermine safely if you have a thyroid problem:

How Does Phentermine Work?

First of all, let’s set some ground rules.

Even though medications can help you with weight loss, they should never be used by themselves.

Weight loss medications, no matter how powerful they are, will never eliminate the need to eat healthily and exercise regularly.

I don’t recommend using weight loss drugs by themselves to try and force your body to lose weight because this tends to cause more problems than it helps.

If you will recall from my previous posts, losing weight and keeping it off requires that your hormones are in balance.

In this way, weight loss is more than just a calorie equation, it’s a hormone-balancing game as well.

If you are still of the opinion that weight loss is all about calorie reduction then stop reading right now and read this post instead.

​Now that we are all on the same page we can move on.

Is this the first time you’ve heard of phentermine before? ​

If so, let me fill you in on some basics.

Phentermine is a prescription medication frequently used for weight loss and it works through these two mechanisms:

  • The first is that it increases your basal metabolic rate (increasing your metabolism helps you burn more calories at rest)
  • And the second is that it reduces your appetite (managing your appetite helps you eat less junk food and stay on your healthy diet, you are planning on eating a healthy diet when you use it, right?)

If you are coming from the mindset that calories are the most important thing when it comes to weight loss then this will sound great to you.

But you can’t forget the importance that hormones play in the weight loss equation.

And it is the impact that phentermine may have on your hormones that can lead to problems down the road (more on that later).

Phentermine acts to increase your metabolism by increasing the amount of norepinephrine (adrenaline) in your body (1).

Norepinephrine is an adrenal hormone and it’s also known as noradrenaline.

This hormone is responsible for providing you with that get-up-and-go energy that you need when you are in the fight-or-flight response.

Stimulating the fight or flight response also comes with some other side effects such as a reduction in appetite.

And this makes sense if you think about it.

When you are about to fight for your life (or run for your life, as the case may be), would you really want your body to start having a craving for a meal?

Not exactly.

As a result of impacting this system, taking phentermine may cause patients to feel more energy, increase their basal metabolism, and reduce their appetite.

Sounds pretty good, right?

Not so fast!

This is how it works in patients without a thyroid problem.

But if you are someone with a thyroid problem then there are a few other things you need to consider.


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Phentermine Impacts Your Thyroid And Adrenal Glands

As you know, your thyroid (in conjunction with your adrenal glands) regulates the metabolism of your body.

Patients with hypothyroidism usually have a lower-than-normal metabolism (2) (sometimes as much as 30-40% below normal).

Because of the negative impact that low thyroid states have on metabolism, thyroid patients are already at a disadvantage when it comes to losing eight.

After all, losing weight with a slower-than-normal metabolism is like entering a boxing match with one hand tied behind your back.

Not something I would recommend.

At first glance, you may think that adding phentermine, which increases metabolism, would be a good idea.

Unfortunately, it isn’t that easy.

Taking phentermine when your thyroid is untreated puts excess strain on your adrenals which can ultimately make thyroid function worse.

Remember that your thyroid gland and adrenals function as one unit (3)!

If something drags down your adrenals it will also drag down your thyroid.

So putting extra stress on this system, especially if it is already impaired, is not a good idea for most thyroid patients.

This doesn’t mean you can’t use it, it just means you need to be cautious when you do.

You can take steps like pre-treating your adrenals (or treating them as you take phentermine) and ensuring that your thyroid medication dose is optimized before you start taking it.

Doing these two things will put you on equal footing with those people who don’t have a thyroid problem and will help the medication be more effective.

In some cases, especially in those with severe fatigue, it may make sense to support your thyroid for 4-8 weeks before you start taking phentermine just to ensure you don’t cause more harm than good to your adrenal glands.

To see if your physiology can handle phentermine answer these questions:

​Can Your Thyroid Handle Phentermine?

  • Is your basal body temperature < 97.8? – A low basal body temperature indicates that your thyroid dose is not optimized.
  • Are you taking T4-only medication like Synthroid or levothyroxine? – Many thyroid patients taking T4-only medications are underdosed.
  • Have you had a complete thyroid lab panel and are your thyroid lab tests optimized? – If your thyroid lab tests are not optimal then you know that your thyroid function is not optimized.
  • Do you still have hypothyroid symptoms? – If you are experiencing persistent low thyroid symptoms while taking thyroid medication then you know your thyroid isn’t optimized.
  • Do you have palpitations or feel like your heart is racing? – Symptoms like a racing heart or heart palpitations may indicate your thyroid medication is too high.

If you answered Yes to any of these questions then it would not be a good idea to take phentermine until they are addressed!

In many cases, slight adjustments to your thyroid medication dose will probably be necessary.

You might also find that changing to a completely different thyroid medication, one that contains T3, may be necessary as well to optimize your thyroid.

Alternatively, you can also try to optimize your thyroid the all-natural way but note that this process will take time.

Can Your Adrenals Handle Phentermine?​

In addition to your thyroid function, you also need to make sure that your adrenals can handle the extra stress put on them by phentermine.

You can do a quick and dirty adrenal health test by asking yourself the following questions:

  • Are you dependent upon taking adrenal supplements like adrenal adaptogens or adrenal glandulars for energy?
  • Do you have any of the symptoms of adrenal fatigue like feeling wired but tired, salt and sugar cravings, a 2 pm crash, decreased sleep, weight gain, and the inability to tolerate stress?
  • Are you dependent upon caffeine to get up and go?
  • Are you taking hydrocortisone or other steroids to support your adrenal health?

If you answered yes to any of these questions then you may want to pre-treat your adrenals prior to using phentermine.

You can do this by taking certain adrenal support supplements, eliminating stressors in your life, eating a healthy diet, taking advantage of low-intensity exercises at night, carbohydrate cycling, and using meditation.

Optimizing your adrenal glands for 1-2 months prior to using phentermine may be ideal for many thyroid patients.

How I Recommend Using Phentermine

Once you’ve confirmed that your thyroid and adrenal glands can handle phentermine, the next thing you need to do is make sure you are using it correctly.

As I said before, phentermine by itself doesn’t actually balance your hormones or lead to lasting weight loss.

But it does have some interesting side effects that we can exploit to make balancing your hormones easier.

We can do that in a couple of ways:

  • By augmenting treatments designed to reverse leptin resistance
  • By augmenting treatments designed to lower insulin resistance
  • Use it in conjunction with fasting protocols such as intermittent and prolonged fasting

Using phentermine in this way allows you to take advantage of one of its primary side effects which is appetite suppression.

This side effect can be very helpful in patients who suffer from intense food cravings (like those with leptin resistance) or in patients who need to be on fasting protocols because of insulin resistance.

As you may know, the key to reversing insulin resistance is reducing insulin levels, and there is no better way than fasting.

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One way to take advantage of this benefit without causing more problems with your hormones is to only take it when you are fasting.

Using it in this way allows for easier fasting days and doesn’t put you at risk of consistent calorie restriction which may cause problems with reverse T3.

Do you see the difference between using this medication by itself for weight loss and using this drug to balance other hormones for weight loss? ​

​There is a big difference!

How Not to Use Phentermine​

Unfortunately, the wrong way to use phentermine is the most common way that it is used.

Most people believe that taking the medication will reduce their appetite which means they won’t eat as much which means they will lose weight.

Remember that this does not lead to long-lasting weight loss and about 98% of people who try this type of diet ultimately end up gaining the weight back (4).

The biggest mistake you can make is using phentermine to reduce your calories for a prolonged period of time while still eating poor-quality foods, just less of them.

This method of use will result in further thyroid damage (5) and weight gain once you stop the medication.

Beware of this trap!​

The traditional advice is to take phentermine daily for several months and then give yourself a holiday.

This holiday is supposed to give your body a break and resensitize it to the medication.

I’ve seen far better results when phentermine is used just a few days each week instead of 7 days per week.

This method comes with built-in drug holidays (breaks from the medication) and doesn’t cause the same hormone and thyroid problems that consistent daily use does.

If you are determined to take it daily for a long period of time make sure that you use it at most 5 days out of the week and take a 1-month break every 2 months or so.

Doing this will allow your receptors to re-sensitize to the medication and keep it working for you longer. ​

Side Effects to Watch Out For

Even though phentermine can be beneficial does not mean that it will be for every individual.

In my experience up to 15-20% of patients don’t tolerate it well due to a variety of side effects. 

The most common side effects that I see in patients include the following:

  • Insomnia – This is a big one, do not take this medication if it keeps you from sleeping. A lack of sleep leads to weight gain (6)!
  • Worsening Fatigue – This is what happens when you take it without treating your adrenals or thyroid first.
  • Fatigue in the morning with bursts of energy at night – Another sign that your adrenals are not ready for this medication.
  • Irritability
  • Dry mouth
  • Palpitations or racing heart
  • Hair loss
  • Decreased libido

Phentermine can cause additional symptoms that are rarer including (7):

  • Chest pain
  • Mental changes
  • Dizziness
  • Tremors or trembling of the extremities
  • Shortness of breath
  • Weakness
side effects of phentermine to watch out for

If you experience these side effects you can try reducing the dose by half, or even taking the medication every other day (or only on fasting days). 

But don’t continue taking it if your symptoms don’t resolve with these changes.

It’s not worth impairing other systems in your body to lose a couple of pounds. 

Don’t take Phentermine Without Taking These Supplements

If you currently have hypothyroidism or Hashimoto’s and you are considering taking phentermine, it’s a good idea to take a few supplements with it.

Here are a few of my favorites and why they should be considered:

  • Adrenal support with a combination of adrenal glandulars and adrenal adaptogens – This supplement was designed just for thyroid patients to help support the adrenal-thyroid connection.
  • Glucomannan powder – Glucomannan is a dietary fiber that expands when introduced to water. It’s another helpful supplement that you can use to safely manage your appetite.
  • Berberine – Berberine is a plant-based compound that has been shown to assist in building muscle mass and lower blood sugar.
  • Glycosaminoglycans – Glycosaminoglycans may help sensitize your body to leptin while also reducing inflammation.
list of adaptogenic herbs that can be used with phentermine

Combining these supplements with proper thyroid medications (like Naturethroid or liothyronine) balances both your cortisol and thyroid levels.

You can (and probably should) take it a step further by adding in regular exercise and a fasting protocol.

Combining all of these treatments together will put your body in a position to burn fat and build muscle while ensuring that your thyroid and adrenal glands stay happy!

​Wrapping it up

Phentermine isn’t a magical medication that will help every patient lose weight but it definitely has the potential to help some when it is used correctly.

My favorite side effect of this medication is appetite suppression which can be used in conjunction with fasting to reverse insulin resistance and leptin resistance which both plague thyroid patients.

Even though it can be helpful in some people it can also cause more harm than good in others, especially if it’s used in patients who are being undertreated for their thyroid or in patients with untreated adrenal fatigue.

Now it’s your turn: 

Have you used phentermine before?

Did you feel that it helped you or hurt you?

Did you try taking it in the way mentioned above or did you use the conventional method?

Did it work for you long-term or did you eventually regain back the weight you lost while you were on it?

Would you recommend it to other thyroid patients?

Leave your questions or comments below!

Scientific References








thyroid patients should be cautious using phentermine

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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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76 thoughts on “How to Safely use Phentermine with Thyroid Problems”

  1. I so appreciate you and your blog
    I have a nodule on my thyroid I have every single symptom of thyroid and adrenal fatigue my blood test for thyroid issues come back in normal range over the past two years I have gained 30 pounds I am looking into taking Phentermine would you recommend that I do so even though I have every single symptom of thyroid disease my endocrinologist is just watching my symptoms but not treating them because my blood tests are coming back okay I appreciate you your time and your advice thank you peaceful day to you

    • Hey Sheshe,

      I don’t think using phentermine would be a good idea in your situation. If you were to take it now you would probably lose a few pounds here and there, but once you stopped it would most likely come right back. It is certainly NOT a long term weight loss solution by itself.

    • Just read this article and will read the previous one you recommended regarding Phentermine.
      I have a question. I was told my cortisol levels were extremely low. (Surprising since I’m a 45yo female that I feel I’ve been stressed since birth) so my endo dr. immediately put me on hydrocortisone pills. Would Phentermine not be recommended in my case for weight loss because of the low cortisol and the pills?

  2. Dr. Childs,

    I’ve been struggling for the past 10 with hypothyroidism, adrenal fatigue, and fibromyalgia. I used phenthermine in the past, which worked great while I was on it, but after 3 – 4 months, all the weight bounced back! So I decided not to used again, but my fatigue and exhaustion is driving me crazy! No doctors have figured it out yet how to help me.

    • Hi Libby,

      Great point. If you use phentermine incorrectly then all the weight that you lose while taking it will simply come back once you stop.

  3. This is a nice blog informing you about thyroid and phentermine. This is my question… I just started taking phentermine HCL 30 mg now and its been a week, but I also have Hashmito Thyroiditis and Graves. I have 1/3 of my thyroid left after surgery so I was wondering about the DFS to take with the phenthermine because of the fatigue and trying to exercise. I have been off thyroid medicine for over 2 years because it was over medicating me so I just take b-12 pills and biotin for energy. I need to lose weight so that was the purpose of going on phenthermine. Your thoughts.

    • Using phentermine in the conventional way will lead to some weight loss initially but it will all come back once you stop the medication.

  4. Dr. Child’s,

    First off, your website has been a great resource and I’ve learned a lot. I’m currently taking 3/4 grain Naturethroid and have been treated over the last 3 months with adaptegens to support my thyroid and adrenals. My question is this, if I was to do alternative day fasting (36 hours) and take the 30 mg phentermine I currently have at home, how far apart from this dose do I take the Naturethroid? Last I checked, my fasting insulin was 7.2 and I’d like to use intermittent fasting to bring that down. In addition, I’m eating a ketogenic diet of 20 or less carbs a day and test my blood ketones regularly to make sure I’m in ketosis. Even with this, my weight remains stable and I haven’t been able to lower that set point through the keto diet alone. But only by fasting. My guess is, once I can lower the fasting insulin through intermittent fasting, the weight will start to come off much easier. Your advice is appreciated!

    • I was wondering if the licorice root or Korean ginseng would help me with the phentermine for energy and weight loss. I have hashimoto and graves and 1/3 of my thyroid left but I don’t take thyroid meds since it was over medicating me

  5. I just had my fasting insulin done and it’s 7.1 and my leptin is 19.5 and A1C is 5.7…with this being the case, will fasting on the weekends with phentermine (Friday, Saturday, and Sunday) improve the leptin resistance? I understand fasting is great to improve insulin sensitivity but what does it do to leptin sensitivity?

  6. So I just started phentermine 18.75 mg day. I also take NDT for my hashimotos. I love the energy Phen gives me, but does any weight I lose on this automatically come back when I stop? I eat really healthy and exercise. I just haven’t heard of anyone keeping the weight off after stopping the pills.

  7. Hello,
    I was diagnosed with hyperthyroidism and anemia. Is it OK to take phentramine with those conditions? I have not lost any weight with the hyperthyroidism. Also, I am extremely dizzy. Is it OK to take? Thank you

    • Hey Liv,

      You should consult your primary care physician but in general I would suggest that it would not be a good idea to use phentermine with hyperthyroidism as that may put too much demand on your heart and lead to damage over time.

  8. My husband was on Phentermine for over 8 YEARS!!! He has now been off of it for at least 5 years but his body has never been the same. Initially he lost about 50 pounds and maintained that for the first few years. Then the weight just climbed back up (even on the med). He is now 48 years old and his body is incredibly resistant to weight loss. He is 5’10” and 210 pounds (most of the weight sits in his round distended abd).We have tried every form of healthy eating with NO change-Paleo, Ketogenic, well balanced, low calorie, etc. We see a functional medicine NP now but her knowledge seems limited with Phentermine (in fact their practice does prescribe it). My husband is currently being treated with Naturethroid, Leveothyroxine, Testosterone and Estrogen blocker. We have also tried lots of supplements, probiotics, allergy food testing, iGG, probiotics. Any suggestions on what we should do next? I have been unsuccessful in finding any studies on how to reverse the damage done by his long term phentermine use. Are there any you can direct me to so I could provide to our NP? I wonder if trying to support his adrenals would help. All of his glucose numbers are WNL but I think on the high side. Any suggestions would be greatly appreciated.

    • Hey Karen,

      Most functional medicine provider consider medications like phentermine to largely harmful long term (and some of that is warranted), but there are still ways to use the medication effectively without the damage that may result.

      It’s hard to say that his metabolic damage was caused purely by phentermine alone, especially if he has concomitant insulin resistance and hypothyroidism. I would recommend you look into fasting insulin levels (and if those are normal then 2 hour post prandial insulin levels). In addition I’m not really a huge fan of the combination of levothyroxine + NDT. It seems that he may have several hormone imbalances that are not being addressed correctly.

  9. Dr. Childs,

    IIn your experience, which is better for fat loss while using phentermine, extended fasting (i.e., 3 day fasts) or alternate day fasting? I’ve been fasting by having my last meal on Thursday evening and then taking a phentermine Friday and Saturday and then resuming eating a keto diet on Monday. I’ve been doing this since Thanksgiving weekend and have lost 13 pounds. What are your thoughts?

    • Hi Dawn,

      It really depends on your body, your appetite, your current metabolism and so on. Some people do well on extended fasts while others should avoid fasting completely. I usually make that decision based on a number of factors including past medical history, weight loss goal and so on. I wouldn’t say one is better than the other as a general rule but that one may be best for your body.

  10. I’ve been taking levothyroxin for 5 years now and my weight has been stuck between 133-140 every day it fluctuates by 4-5 lbs. A month ago my Dr finally prescribed phentermine for me because I was just stuck with my weight even with 45min to an hr of workout 5 times a week. My first week I finally got down to 131. Now I’m back at 133-137. I eat healthy and my portions are small……please tell me what I should do next.

  11. I have half of my thyroid the other half was removed due to a tumor the size of a tennis ball. I now have on the half of thyroid i have left two nodules one on the base, and one on the right side. In addition i also have a tumor on the right adrenal gland and a cyst on the left. I am allergic to synthriod and have been put on tirosint. I just went for lab work and my creanitine came back minor abnormal as well as my t3 and my acth. They were all just slightly higher than what they should be and i go back to my endo on may 23rd. I have been on adipex for the last year off and on and have managed to keep off 30 pounds. I am suppose to return to my PCP tomorrow to be put back on it. Any thoughts would be appreciated.

    • Hi Bonnie,

      In general you don’t want to stay on phentermine for an extended period of time as it may cause issues in cardiac tissue and so on. In cases such as yours it may be better to explore newer and more efficacious weight loss medications with your physician.

  12. I was diagnosed with hyperthyroidism can I take Phentermine or will my doctor prescribe Phentermine in this condition?

  13. Hi Dr Childs,
    My endocrinologist is considering prescribing Phentermine for weight loss, but I’m hesitant based on the many comments that the weight always comes back. I have Hashimoto’s (treated currently with levothyroxen and liothyronine) as well as insulin resistance (and take Metformin for that). Some years ago I was also diagnosed with leptin resistance as well. My naturopath has told me I have adrenal fatigue – I do take Ashwaganda.

    My question is – for long term weightloss, it sounds like you recommend intermittent fasting for the phentermine to work with thyroid issues – is that correct? Thank you!

    • Hi Rain,

      If phentermine is going to be used at all then that is probably the best way to use it – in an intermittent fashion. If you use it consistently each day to suppress your appetite then any weight you lose while taking it will come back once you stop.

      Hope this helps!

  14. Hi Dr Child’s

    I have Hypothyroidism and PCOS. I am being medicated for both. I wanted to know what the ideal dosage is for weight loss when you have hypothyroidism?

    Thank you

    • Hi Liv,

      I wouldn’t say that there is an “ideal” dosage for weight loss based on medical conditions but rather based on the individual and their sensitivity to the medication.

  15. Hi Dr. Childs,

    I’m 31 and found out earlier this year I have hypothyroidism. I’m so happy to have found your website, I can’t wait to read more! My PCP prescribed me 100MCG of Levothyroxine, which now shows my thyroid levels are normal.

    My question is: How do I tell if my adrenal glands are good to go? I have access to my blood test results if it’s on there I can look – or can they not be tested by blood tests?

    I want to start on Phentermine but want to make sure my adernal glands are okay and/or start taking the natural supplements to get them in order.

  16. Hi
    I was diagnosed with hyperthyroidism 5years a go and they did a radioactive iodine which made me hypo. I take medicine everyday and have my thyroid under control. My tsh is at 3.33
    My doctor gave me Phentermine, I only took it one day and had the worst headache I have ever had. I have not taken it again. I don’t know if maybe taken half would help me with the headaches. What do you recommend

  17. What a fabulous blog – very informative (and i have been searching for all sorts of information online). I have put on a tremendous amount of weight due to thyroid issues and have started on Levothyroxine – i need to try again in losing weight which has been incredibly difficult – could you suggest anything that i could take to help with the metabolism – I have a shaking machine now and will be increasing walks and exercise – I’m still working out the right dosage of my thyroid meds but would like to help my body get back to normal – can you advise me of anything??… Thanks again for putting this information out int he world it really is a help to those of us having to deal with these issues.

  18. I had a thyroidectomy in December 2017 due to cancer. I believe my endocrinologist has my hormones leveled out now at 175 mcg Synthroid and 5 mcg Cytomel, however I can not drop the weight. I was wondering if Phentermine might be an option for me?

  19. Hello Dr Childs,

    I’m a 30 year old female. Until the last six months I have always yo-yoed in weight. But since the death of my mother and a significant break up I have always found it easy enough to lose weight. I used Phentermine a year and a half ago loose 15kgs and it stayed off fine. This time when taking Adipex I seem to be putting on weight even with the drugs and all of a sudden have belly fat – which has never been a problem for me before. Is it possible that I am retaining water? Also – the Phentermine I was taking before was in the form of Duromine rather than Adipex and my Adipex dose is much lower.

    I’m very confused and concerned. I am eating well and walking for at least four hours a day and I just keep swelling. Any information would be very helpful. Thank you.


  20. What I would like to know is “when” to take the phentermine with regards to levothyroxine. I have Hashimoto’s, have been on levothyroxine many decades and always take it when I wake up. When do I take the phentermine?

  21. Hi,

    I am a 28-year-old woman, and I had my thyroid completely removed in 2014 since then I have gained about 40 pounds so my dr. recently prescribed me Phentermine to try to lose weight. Is there any advice you can give me while on this medication? I am currently taking levothyroxine 137 mg.

  22. I’ve been taking phentermine for about four months and recently found after going to my PCP for having to go potty so many times during the night. He did thyroid TSH test which resulted in a .230 (L) value with normal range being 0.450-4.500ulU/mL then a thyroid panel with all of those numbers being in range T4 7.7, T3 27, FTI 2.1 – could the phentermine be the cause or play into my TSH number being .230? I had an ultrasound on my thyroid yesterday and won’t know the results until next week. Thanks!

  23. Hi Dr Child’s,

    I’d like to take phentermine for 2 months. My S TSH is 0.30 and my S FT4 is 12.7. It’s been consistently like that for years and I have no thyroid symptoms. Would this drug be safe?


    • Hi Stella,

      It depends on how you would use it. If you use it daily to suppress your appetite then it probably will cause problems long term.

  24. Hello Dr. Childs,
    I am 24 years old and have hypothyroidism. I recently went to my doctor and he put me on levothyroxine and recommended me to take phentermine for the next 3 months until I see him again. I just started taking my levothyroxine, how long should I wait until I start taking the phentermine? thank you!

  25. I had hyperthyroidism, then my doctor treated me and gave me too much medicine when I got an iodine ablation. Now I have hypothyroidism and I’ve gained almost 45lbs. I take 125mg of Levothyroxine. My doctor prescribed me 37.5mg of Phentermine to help me lose weight. What’s the best way to take this medicine so that the weight doesn’t come back once I’m off of it, since I no longer have a thyroid?

  26. Hey, so currently I’ve been struggling with my weight. It was good until recently I’ve gained around 30 pounds. Next month, due to my religion I’ll be fasting for the whole month, meaning no food or water from sunrise till sunset. I have hypothyroidism and am currently taking levothyroxine. I really need to lose my weight, as it’s really affecting my self-esteem. Do you think taking phentermine in my case would help? Of course, when I do eat my meals, I will eat healthy foods to replenish my body and drink milk and water. I just really want something to work and don’t want to hurt my body or lose weight and gain it all back.

  27. Dr. Childs,

    I used Acxion in the past for a short period of time and it helped me lose some weight. Now that I’m older I’m having some under active thyroid issues and have been on Levothyroxine for a year now. I’m currently taking 77mcg and my thyroid level has been under control. But in the last year I have gained 15lbs that I cannot get rid of no matter what I do. So I started taking Acxion this week to help me with that. A 15mg dose is perfect for me, when I tried the 30mg it was too much. But wanted to know your opinion if its safe for me to take while taking Levothyroxine and what’s the best way of taking this medication.


  28. Hi. Thank you for the information. When I was turning 50, I went on Phentermine. It was great. Lost the weight, no side effects. Went off it and I didn’t watch my weight, gained it back slowly. Now 10 years later, I just turned 60, I want to do Phentermine again. Six years ago low Thyroid, now taking Levothyroxine 50 MCG. Results from recent annual lab test: TSH = 1.380; Thyroxine (T4) = 9.3; T3 Uptake = 30; Free Thyroxine Index = 2.8. You wrote Levothyroxine can cause weight gain? What are your thoughts and suggestions? Thank you.

  29. Thank you for this information! I have been on Phentermine for 1.5 years to treat ADD symptoms. I’m 40 years old. It’s probably been 25 years, I’ve struggled with untreated Hashimoto’s. About six months, I went gluten-free along with dairy-free (4 years). I’ve been able to lose weight and relieve some of the inflammation in my body. You are so right, though, about all the negative side effects of Phentermine. None of the physicians I have seen have told me to get off of Phentermine to stop the weakness/numbness in my arms and legs, insomnia, or heart palpitations. They think those side effects are caused by anxiety and tell me to take a benzo or change my antidepressants around. Here I’m left with untreated hypothyroidism. I’ve stopped the Phentermine to get my lab work to come out the correct way to prove I was primarily using it because my thyroid was shot, and I was exhausted. I see a new doctor soon. Thank you for giving me hope!

  30. Dr. Childs, I had my thyroid removed and having problems and need a doctor like you. Could you tell me if there is a doctor in Alabama or northern part of Florida you would recommend to me.

    Thank you,
    Sandra Glass

  31. I just started on phentermine again after taking a very long break. This time, my endocrinologist prescribed me the phentermine alone without the use of topamax. With my PCOS and hashimoto’s, I’ve always had a hard time losing weight. I’m 44 and obese. I’m 5’4 / 170 lbs with a waist size of 33.5 inches. I’m vegetarian, eat very healthy. I’m now incorporating gluten /dairy free to help with eating less inflammatory foods. I’ve been up and down for the last 12 years. I also have an active job and work out with weights once a week. I know it’s not enough but I also fight fatigue. I hate using phentermine because it’s a crutch but I’m desperate to lose weight. My TPO antibodies were 56. My thyroid medication is levothyroxine 25mcg. I take a lot of supplements as well.

    • Hi Nicky,

      I would strongly caution against using it in that way. You are trading short-term weight loss for long-term problems.

      You can find out how to lose weight and keep it off here:

      How you use it is up to you and your doctor but I can tell you from experience that it tends to cause long-term problems in thyroid patients.

  32. I have had ideal thyroid levels for 5 years with NP thyroid and T3. I gained 30lbs in 2020 on Zoloft, switched to Wellbutrin, quit gaining but couldn’t lose. Started phentermine 4 months ago, have lost 27 pounds. 6 weeks ago I checked ferritin due to symptoms and it was 9. I’ve been taking iron since and feel amazing- best I have in 15 years. Now- ferritin good at 40, D good, insulin and glucose great, but I’m slightly hyperthyroid now. My gut tells me thyroid is functioning better due to iron. Thoughts? Phentermine raising thyroid? Or iron?

  33. What do you think of PhenQ. Tried your weight loss program, for me two many steps in taking all the pills with your program.

    • Hi Norma,

      A quick glance at PhenQ suggests that there’s nothing special about it. As a good rule of thumb, if you can’t find a product on Amazon, then it’s probably not a good idea to buy it. That’s because businesses can’t manipulate reviews on amazon, but they can on their website.

      The reality is that if you want long lasting weight loss, you’re going to need a combination lifestyle changes, dietary changes, multiple supplements, an exercise program, and potentially hormones or medications. It will require time, effort, and energy consistently over many months.

      I would run, not walk, away from anyone or any product that tries to suggest otherwise.

  34. This is a great article. I have been wondering about taking this. I had a complete thyroidectomy in 2012. I am on 137mg of levo and I need to lose about 60 lbs. I get my blood work done every three months. I do also take a high blood pressure med amlodepine. Would I be able to take phentermine and topamax.

    • Hi Trish,

      They can be used together, yes, but whether or not that’s a good idea for your own personal situation will require further evaluation.


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