Prescription Medications That Block Thyroid Function

Prescription Medications That Block Thyroid Function (Avoid These!)

Are Your Other Prescription Medications Damaging Your Thyroid? 

If you have thyroid problems then there's also a high chance that you are taking OTHER prescription medications. 

But did you know that these prescription medications may actually be causing issues with your thyroid?

It's true. 

While those prescription medications may be helping other conditions in your body, you should never forget about the potential negative side effects that also come with them. 

And there are MANY medications that negatively impact your thyroid function in various ways

Today we are going to discuss a list of prescription medications that you should watch out for if you have thyroid problems AND if you are taking thyroid medications

You will learn how these medications negatively impact thyroid function, what these medications are used to treat, and how to make sure your medications are not interfering with thyroid medication (if you are taking any).

Let's jump in: 

Download my Free Resources:

Foods to Avoid if you have Thyroid Problems: 

I've found that these 10 foods cause the most problems for thyroid patients. Learn which foods you should absolutely be avoiding if you have thyroid disease of any type. 

The Complete List of Thyroid Lab Tests:

This list includes optimal ranges, normal ranges, and the complete list of tests you need to diagnose thyroid hypothyroidism correctly!

Download more free resources on this page

4 Ways That Prescription Medications Interfere with Thyroid Function

There are 4 main categories in which prescription medications can interfere with thyroid hormone function. 

These categories are all different but they are all required to function optimally in order for your thyroid to do its job. 

Different medications cause different problems with thyroid function, so be sure to compare your medications to those listed below. 

And when I talk about thyroid hormone function what I really mean is how well your thyroid is working in your body. 

If your thyroid is not working properly then you will most likely feel it as you experience thyroid-related symptoms (usually hypothyroid symptoms). 

Category #1. Medications that Block T4 to T3 Conversion. 

The first place that medications can interfere with thyroid function is through inhibiting or blocking something known as T4 to T3 conversion

T4 to T3 conversion is often referred to as thyroid conversion and is probably one of the most important concepts as it relates to thyroid function generally. 

This conversion refers to taking the inactive T4 thyroid hormone and converting it into the active T3 thyroid hormone. 

If this process is blocked or slowed down in ANY way then you will simply not have enough T3 in the body. 

If your T3 levels fall then you WILL experience low thyroid symptoms. 

Here are prescription medications which BLOCK this process (or slow it down):

  • Methimazole - Methimazole is designed to treat hyperthyroidism (high thyroid) so it's not surprising that it blocks thyroid function. What you need to understand, though, is that taking methimazole will take your thyroid from the hyper state to the hypo state and you may experience the symptoms of hypothyroidism in the process. 
  • PTU - PTU is another medication used to treat hyperthyroidism but it isn't used as much nowadays as methimazole is preferable. 
  • Beta blockers - Another big category is that of beta blockers. Beta blockers are commonly used to treat high blood pressure but they are also used to treat other conditions such as tremors and heart disease. If you have high blood pressure and you have thyroid problems make sure that you are not taking a beta blocker! If possible, ask your doctor to switch to a different blood pressure lowering medication (this may not be possible in every situation but it's worth asking). 
  • Narcotics - All types of prescription narcotics (such as Vicodin, Percocet, and more powerful narcotics) can all block thyroid conversion. What you may not realize is that low thyroid function can cause chronic pain which may complicate this issue further. Over the counter anti-inflammatories, like ibuprofen, do not cause this issue and are preferable if you are trying to prevent thyroid interference. 
  • Antidepressants - This is a HUGE one! How many of you are taking antidepressants for depression and didn't realize that it can actually block this conversion process? A great many thyroid patients are prescribed antidepressants because they experience depression (a symptom of low thyroid) which may worsen thyroid function and make their depression more difficult to treat. The best way to solve depression if you have thyroid problems is to focus on the thyroid issue FIRST. 

Category #2. Medications that Block TSH Production. 

These medications work by interfering with how your brain communicates with your thyroid gland. 

What you may not realize is that thyroid function starts all the way in your brain in something referred to as the hypothalamic-pituitary axis. 

This axis is how your body communicates with other hormone systems and it's this system that tells your body to produce hormones (or not). 

There are medications that BLOCK this process from working by directly interfering with pituitary function. 

These medications can be difficult to trace because pituitary problems are not often seen when you check your thyroid lab tests.

  • Steroids - Steroids are often given to patients as prescription medications to help LOWER inflammation in certain diseases. Most doctors know not to use these powerful medications long-term, but it may be necessary for some individuals. Steroids have a suppressive effect in the brain which reduces TSH production and this effect gets worse the longer you use the steroids. By the way, this side effect can occur if you are using topical steroids as well! Topical steroids in gels or creams are typically not absorbed very well (1) but they can be depending on where you place them. If you put topical steroids on your face, under your eyes, around your nose or lips then you are absorbing a lot more than you think. 
  • Dopamine agonists - Dopamine agonists are usually used to treat Parkinson's disease so they are not very common, but they can suppress TSH function (2). 
  • Metformin - Metformin is a VERY common prescription medication used to treat diabetes and insulin resistance. Metformin is so common because it's the drug of choice for diabetes and it works well with almost all other diabetic medications. So there is a good chance that you are taking this medication if you are pre-diabetic or diabetic. The problem with metformin is that it can reduce TSH production (3) and make your thyroid look better than it already is. You can get by using the smallest effective dose of metformin as possible. Doses around the 500 to 1,000mg range tend to be better for your thyroid compared to the 2,000 to 2,500mg/day doses. 

Category #3. Medications that Block Thyroid Hormone Production from the Thyroid Gland. 

Prescription medications can also directly block thyroid hormone production from the thyroid gland. 

These medications work by damaging the thyroid gland directly. 

If your thyroid gland isn't working properly then it doesn't matter if your brain is communicating with it, because it simply won't be able to respond. 

join 30,000 plus thyroid patients

If you have a problem with your thyroid gland then your thyroid will NOT produce T4 or T3 thyroid hormone when prompted and you may start to feel hypothyroid. 

These medications are typically rare, but you should be aware of them. 

  • Potassium iodide - This type of potassium is typically used for dermatology procedures and is not the type of iodine that you are probably familiar with. Unless you are getting frequent dermatologic procedures, it's unlikely you've been exposed to this medication. 
  • Lithium - Lithium is definitely more common because it is frequently used to treat mood disorders as well as bipolar disorder. Lithium, especially if used in high doses and for the long term can permanently cause thyroid damage (4). For this reason, everyone who uses lithium is required to have their thyroid checked at regular intervals. What's interesting here is that certain thyroid medications (like Cytomel and liothyronine) can actually help treat bipolar disorder. So if you are using lithium for bipolar disorder and you haven't tried those therapies you may want to look into them! 
  • Amiodarone - Amiodarone is usually used to treat certain heart conditions and is not frequently used nowadays. Like lithium, doctors know that amiodarone can cause thyroid problems so they usually keep an eye on thyroid function when you are taking it. 

Category #4. Medications that Block Thyroid Medication Absorption

The last section is for those prescription medications which actually interfere with thyroid hormone. 

The other medications that we've discussed cause problems with thyroid function, but this is completely different from medications which interfere with thyroid medication. 

In this section, I am referring to prescription thyroid medications such as levothyroxine and Synthroid (as well as all other brands of thyroid medications such as NDT and T3) which are taken if you have low thyroid function in the body. 

Many people reading this who already have baseline thyroid problems are most likely using some type of thyroid medication but if you aren't, then this information isn't super helpful to you (at least not yet!). 

  • Cholestyramine - Cholestyramine is what is referred to as a binder and it's usually used to help treat conditions like diarrhea. It works by binding to things in the intestinal tract which typically slows down intestinal motility. It's also sometimes used as a detoxification treatment by integrative doctors to help get rid of things you don't want in your intestinal tract. One of the downsides to using this medication is that it can block your thyroid hormone from being absorbed. 
  • Acid blockers - When referring to acid blockers I am talking about all kinds of prescription acid blockers as well as over the counter acid blockers. Things like Protonix, Zantac, or any other medication which blocks acid production in your intestinal tract can have negative consequences on thyroid medication absorption (5). These work by reducing acid production (which can help with acid reflux temporarily) but come at the cost of reducing your stomach's ability to absorb nutrients, vitamins, and even thyroid hormone medications. 
  • Fiber - The fibers I am referring to here are typically used to treat constipation. They work by pushing stool through the intestinal tract to help with bowel movements. But these fibers also have other consequences such as impacting the absorption of medications. 
  • Sucralfate - Sucralfate isn't used very often but when it is it is typically used to treat inflammation in the stomach (gastritis) or stomach ulcers. 
  • Estrogen - Estrogen doesn't directly impact thyroid medication absorption but it can impact how well your thyroid medication is being utilized. Estrogen increases thyroid hormone-binding globulin which can bind to free thyroid hormone and limit how much is available for your body to use. I've included it here because it somewhat closely fits in with these other medications which block thyroid medication absorption. 

Make Sure you Double Check ALL Of your Prescription Medications

The moral of the story is that you should be very aware that prescription medications come with side effects and these side effects may include problems with your thyroid!

My recommendation is to take a close look at all of the prescription medications that you are taking. 

If you find that any of your medications are found on the list above then ask your doctor if you can switch to another type of medication. 

You will find that many times, switching your prescription medication may make a big difference in how you feel. 

And there are plenty of other classes of medications for treatments like high blood pressure, mood disorders, depression, and so on. 

In some cases, these conditions have 5+ different medications to choose from! 

Now I want to hear from you:

Did you know that these medications can cause issues with your thyroid?

Are you taking any of the medications listed above?

If so, did you notice a change in how you feel or how well your thyroid was working after you started them?

Leave your questions or comments below! 

References (Click to Expand)

these prescription medications can damage your thyroid

Dr. Westin Childs

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 45,000+ people have used them over the last 4.5 years. You can read more about my own personal health journey and why I am so passionate about what I do here.

63 thoughts on “Prescription Medications That Block Thyroid Function (Avoid These!)”

  1. I would like to know your thoughts on using betahistine for tinnitus/vertigo and does it interfere with my thyroid medication? And if so, should I stop taking it?

    Reply
  2. Hi, I’m on HRT. Does this mean my Thyroxine is not working well? According to my last bloods my TSH is a little high but my T4 is normal. They do not test for T3 under normal circumstances in the NHS in THE UK

    Reply
  3. I’m taking Mirtazapine which is classified as antidepressant. My PCP has never mentioned that this may interfere with my T3 conversion. Is Mirtazapine one that does interfere? My T3 is low at .78. I have lots of anxiety and take Lorazepam and melatonin for sleep in addition to Levoxyl and Liothyronine. Only other problem has been a lot of hair loss.

    Reply
    • Read the fine print of the medication pamphlet, I just recently notice under the note in the pamphlet that this medication interferes with iodine something Dr doesn’t know tweet about
      I stoped taking it 3 months ago and starting to feel much better, remeron was the brand name of antidepressant

      Reply
  4. Hi,
    I was diagnosed with Graves’ disease and I tried taking all different thyroid meds and have had really bad side effects to them all and felt like crap on them. My TSH is high but my T3 and T4 are both in normal range. Any help to figuring out why I feel like crap taking these meds to the point of anxiety and panic attacks. I have stopped my meds.

    Reply
    • Hi Lisa,

      It’s hard to say for sure without a lot more information but my guess would be that it’s a dose related issue.

      Reply
  5. I’m to be taking Prozac 20 mg and Olmesartan Medoxomil 40 mg and suffer from severe anxiety and should be taking clonazepam per my pcp 1 mg 3x daily as I can’t sleep. I’ve just beep it on Armour 30 mg. Any of this causing problems with Armour?? Thank you

    Reply
  6. I take thyroid medicine called levothyroxine 100 mcg once a day and it’s making me gain a lot of weight, I have hypothyroidism.

    Reply
  7. Hello~ I take 50MCG Levo but feel I could do more. Always been around 115-118 lbs @ 5’4″. need to lose 20-25lbs to get back. What would you suggest?

    Reply
  8. Hello~ I take 50MCG Levo but feel I could do more. Always been around 115-118 lbs @ 5’4″. need to lose 20-25lbs to get back. What would you suggest?

    Reply
  9. Hello Dr. Child’s! There is one more category that I would like information about. It is surgical procedures (ie: Roux-N-Y gastric bypass) and digestive tract disorders that interfere or impair with absorption or dosages of thyroid medications. Would you please update this article or give a link to other articles you have written about this specific concern? Thank you for all the important information you share with us!

    Reply
    • Hi Giovanna,

      You are 100% correct that gastric bypass will impact thyroid medication absorption but I wouldn’t classify it as a prescription medication which is why it isn’t included in this article. Having said that, I still think writing about that topic is a good idea so thank you for the suggestion 🙂

      Reply
  10. I started taking my thyroid meds at night (Tirosint & Cytomel) to be sure they are away from any vitamins. My husband just passed away and my Primary doctor prescribed a low dose of Zoloft (25 mg) during the day and Zanax at night for sleeping. It has only been 2 months since I started. My hair has started to fall out even loosing eyelashes. Of course it could be stress. Should I speak to the primary of my endocrinologist to start to wean myself off of these meds?

    Reply
    • A side affect of Tirosint and Cytomel is hair loss. Have you tried an NDT. I had the same issue when I took synthetics T4 T3. I am very sensitive to them. They even tried giving me Time released, but with it being a synthetic same issues. I am very senstive to synthetic T3. I had always taken Armour 90mg, but for some reason my Doc changed me to NP Thyroid which was recalled for super potency and all my problems started Last year when this happened. I am now back on Armour. Since the switch my hair loss is almost gone in a few weeks, my eyebrows are growing back. I get 90 MG and split them in half. I have started with 45mg in the morning and I will be working my way back up, splitting the other 45 in half and taking smaller doses a couple times a day. Hope you can figure it out and Good Luck

      Reply
    • Hi Rita,

      It’s probably more related to stress but it would still be a good idea to see your doctor and get your labs checked to see if you need to make any changes.

      Reply
  11. Great info as always. Thank you.
    I never had any idea that PPIs could interfere with thyroid med absorption. I also just started HRT via pellets that my doctor slices me and puts into my backside. My TSH has been a little too low for months, but my T3 was good and I think my T4 was slightly low or vice versa. My pcp told me to stop taking the cytomel. I was taking 5 mg a half every other day. It definitely gave me a little more energy and made me less lethargic. So I’m worried that I’m going to get lazy and tired again now that I stopped using it about a month ago.So now I’m just taking my armor thyroid. When I first was diagnosed I was put on Synthroid and then the generic version and they really made me extremely anxious. The armour thyroid has definitely helped with my anxiety levels.

    Reply
  12. Hi Dr. Childs,

    On your list of meds that interfere with thyroid medication is estrogen, which is what I take each morning and evening in bioidentical form, transdermally. Because I want to continue to take estrogen, would you suggest spacing these meds apart a few hours?

    Reply
    • Hi Lisa,

      Estrogen impacts thyroid function because it impacts thyroid hormone-binding globulin. In other words, this effect will still occur regardless of when you take your thyroid medication in relation to your estrogen and regardless of HOW you take your estrogen.

      Reply
  13. An endocrinologist tried treating me for 5 years with not good results. Every time I started to take the Synthroid or Levothyroxine I would have heart palpitations and would have to stop or take it every other day BUT nothing helped. I met a compounding pharmacist who told me I needed estrogen but the bioidentical kind. Once I started taking that, I could take the Levothyroxine with no palpitations. I also take a bioidentical progesterone so I don’t become estrogen dominant. BUT, today I read about how estrogen can inhibit the absorption of my medicine. I’m confused. My labs are normal. I take 75 mg of Levothroxine and 10 mg of Cytomel each day. I take them both in the middle of the night to avoid interference with my vitamins. What say you, Dr. Childs? It’s been years since I’ve been on the estrogen (I’m 69 now) so maybe I could go off of it. Please advise.

    Reply
    • Hi Connie,

      I’m not really sure I follow the question, are you asking if you can get off of your thyroid medications?

      Reply
  14. I was given CORDARONE Amiodarone for A-Fib from 2016 to 2020. High doses of it and loaded several times in hospital.
    The doctors never told me of the side effects nor did any follow up tests. I now have hypothyroidism due to this drug.
    I know that there is a half life and that it remains in my cells and tissues and organs for years after stopping.
    My question is
    How can I detox and will it every leave my body.
    Can the Hypothyroidism be reversed and would I be able to come off my NDT.
    I have gained so much weight due to CORDARONE Amiodarone toxicity.

    I have most of the side effects from it.

    Can or will I be able to repair my Thyroid problems

    Reply
    • Hi Christine,

      Unfortunately, some of the damage may be permanent but there will be no way to know for sure unless you are able to get off of it and see how much thyroid function can be restored. You will need to talk to your cardiologist (or whoever prescribed it) to see what other options are available for your a fib.

      Reply
  15. Thank you for this article! I take Tramadol maybe once or twice per week for chronic back pain. I believe that it is an opioid narcotic. I just wasn’t sure if it is considered one that can block thyroid function. I don’t take it often but I hate to cause more issues for my poor thyroid.

    Reply
  16. Hi….
    As I’ve said before your email topics come at the most perfect time.
    Yes, I understand no calcium, iron or magnesium supplements.
    I did not know “potassium iodide was one of them. I was given a custom iodine supplement ( potassium iodide an iodine titrate = 12.5 mg). My iodine lab went to 859. I stopped but not bec I follow the conservative range. Because people take large amts every day as you mentioned, I do not understand how much is the optimum range to be at. I was going to start back on my iodine today but read this email saying potassium iodide was not good. Now what do I do? Could go back to my Nasent iodine extract at 1950 mcg. Iodine was the cause of my losing T4/T3 per my own testing. It also resolved the headaches I had everyday for years. Always told I was fine. Over a asbestos over. What a bunch of idiots! Always knew it was either deficiency or chemical imbalance. Resolved two major issues. Can’t wait to write on the website about every single doctor I saw.

    Reply
  17. Also….
    As for anti depressants, was going to start Wellbutrin. Search said no interference w thyroid meds. Yes, no?
    I know it’s better to not but I’m not having fun over here.
    Cytomel not working and dose too low. (digestive disorder). Waiting for my dr. to prescribe SR T3 for me. I don’t think he knows allot about compounding.

    Thank you

    Reply
    • Hi Cindy,

      Wellbutrin works via a different mechanism than traditional anti-depressants and shouldn’t cause issues with the thyroid, at least not to the same degree as SSRI’s.

      Reply
  18. My daughter is on anti-depressants. As her mother, I have been on thyroid medication since I was pregnant with her (26 years).
    I would love to see her not have a problem with her thyroid, especially with the T4 to T3 conversion. She should probably ween of her meds??

    Reply
    • Hi Ann,

      In my experience, depression can almost always be treated without the use of anti-depressants and if she can avoid taking them then that would be better for her health overall.

      Reply
  19. I take an BHRT: Bioidentical hormone treatment that is a combo of Estradiol, Progesterone and Testosterone. Is this not good due to the estradiol?

    Reply
    • Hi Martha,

      It’s not really a good or a bad thing by itself. Whether or not it’s good depends on your body and whether or not it helps you feel better. If it does, then you should keep in mind that it may impact your thyroid levels so that should be accounted for.

      Reply
  20. Thank you for consistently providing such empowering, useful information. Is Lexipro considered an antidepressant? It was given to me as an anti-anxiety med but I’m wondering it it could be contributing to my conversion problem. I have tried many different doses but no matter what I go on my T3 seems to hover between the mid-twos and upper twos range. This was the case for a while before I started the anxiety meds but I’m just curious if that could be counterproductive to my goal of trying to optimize my T3. I’ve ordered your thyroid daily essential vitamin in the hopes that maybe that will help something budge. When I first started thyroid meds my body seemed to be converting very well. I’m still trying to figure out how to support it to get it back in a more optimal range. Mainly, I just need that pep back in my step!!!

    Reply
  21. I have been on different thyroid meds since I was 6-7 yrs old. I’m 63. I went on supplements and off of all thyroid meds but still don’t feel well with thick tongue, pain tingling in hands and puffy eyes and weight gain among fatigue. I just read about B12 and I’ve been taking the wrong one. My doctor told me in March 2021 my labs look great. I told him I’m not doing well. So I stopped synthroid. I did try Raw thyroid but that was no help. I am 40-50 pounds overweight and started fasting and auto immune diet. I have had pituitary tumor but now that’s gone.

    Reply
  22. Hi Dr,
    I have had hashimoto’s for 21 years now – medication I take daily
    Levothyroxine 0.05mg x 4pw &0.1mg x 2pw Liothyronine sodium
    / Prolia 60mg/mL injection 2xpa / Hemp oil capsules /
    Is it safe to take Moringa supplement
    Thanks.

    Reply
    • Hi Teresa,

      It’s probably a good thing for thyroid function but there aren’t a lot of studies that show one way or the other.

      Reply
  23. Dr. Childs,
    It seems most of your topic articles are not based on those of us with hypothyroidism due to cancer and total thyroidectomy. Your list of antidepressants seems very short, is that all that I need to be concerned about? I currently take two prescriptions and have for over 20 years. I had my TT 11 years ago. One is an angiotensin II receptor antagonists due to MI in 1998, the other is an SSRI antidepressant medication that works in the brain. It is approved for the treatment of major depressive disorder (MDD) and generalized anxiety disorder (GAD).
    I have taken Protonix for so many years I cannot remember. Surgery is out of the question, I have a hiatal hernia, slow motility, and nutcracker esophagus. Can be very painful so once in a while I do take a Sucralfate that I always take at a time when it won’t interfer with the Armour, and this is the shortlist of meds I take.
    Any additional help would be appreciated.
    Most of what I found in this particular article seems to be related to levo and others of its sort. I am currently taking Armour, not my favorite, but with all the other NDTs facing hurdles, this is what I am stuck with. I did start with levo after my surgery then switched to Nature-thyroid.

    Reply
    • Hi Rhonda,

      All of my articles that talk about hypothyroidism are also relevant to those without a thyroid from any cause. So this information is 100% relevant to you as well as most of my other articles (95%+).

      Not all anti-depressants cause issues but those that are SSRIs or SNRIs have the potential to.

      Reply
  24. Hi Dr. Childs,
    I was medicated liotirinina (25mg) and and also Levotiroxina Sodica(100mcg) and I take half of each tablets in the morning before any meals. And as you said in your article yes, I also was given Metformina (850mg) 1 pill a day. It has been almost a year since I’ve started to take them but unfortunately they don’t help. The results in my test blood are almost the same. And every time I have an appointment with my doctor I ask him to change the medicine . Now after reading your article I understood why I have no results.
    Can you suggest me anything else instead of those medications?
    Thank you so much.

    Reply
  25. Is Setraline HCL 100mg. (1and 1/2) daily ) (Zoloft ?) one of the anti-depressants on the “avoid” list ?

    AND – I take pramipexiole nightly for restless legs syndrome — a problem for thyroid ?

    Reply
    • Hi Karen,

      Yes, sertraline is an SSRI which means it’s on the list. I am not sure about pramipexole, though, as I haven’t studied it.

      Reply
  26. Thank you so much Dr. Childs! What are your thoughts on calcium channel blocker medication (for example, amlodipine) used to treat high blood pressure? It does not appear on your list of potential harmful medications for the thyroid. Is there any chance it may block iodine and its functions related to the thyroid? Thank you!!

    Reply
    • Hi Jackie,

      As far as I know, calcium channel blockers do not interfere with thyroid function. In terms of treating hypertension, it’s always best to try and reverse it, though, if possible.

      Reply
  27. Hi Dr. Childs,

    I was diagnosed with Graves in January 2020 and have been taking Methimazole since. Lately, I have been trying to follow your recommended diet of clean eating, I try really hard, but not the best at it. I’ve gone down from 15mg to 2.5mg every other day now.

    The TSH levels were high the last 2-3 times I got lab work done. Could this be because I’m on Methimazole?

    -Should I stop going to my Endo and stop Methimazole altogether?
    -What can I do to balance out my TSH and TSI so my Endo can take me off of Methimazole?

    Reply
    • Hi Riley,

      I’m not able to give recommendations on how to adjust your dose of medication but if your TSH is increasing that means you may not need the methimazole any longer.

      Reply

Leave a Comment

0
Your Cart
Your cart is emptyReturn to Shop
Calculate Shipping