9 Supplements That Hurt Your Thyroid: Are You Taking Any?

If you know me then you know that I’m a huge fan of using thyroid supplements to augment existing thyroid treatments.

Thyroid supplements, as long as they are used correctly, can seriously help improve your overall quality of life by improving thyroid function. 

But this assumes one very important thing:

You are using the right supplements for your thyroid. 

Because, while some ingredients can certainly help your thyroid, there are others that can easily cause more harm than good.

Let’s talk about the supplements and ingredients that thyroid patients should be cautious about using right now:

Exercise Caution When Using These Supplements

#1. Iron

The first on this list is iron. 

Iron is actually an incredibly important nutrient for your thyroid but it’s what I call a Goldilocks nutrient. 

You need just the exact right amount in order to feel better and improve your thyroid. 

How does iron impact your thyroid?

In many ways, but the most important is its impact on thyroid hormone function (1). 

Low iron leads to decreased thyroid function which, in turn, leads to reduced iron absorption which continues in a vicious cycle until you either fix your thyroid or take an iron supplement.

And this vicious cycle continues until you stop it by either fixing your thyroid or taking iron.

But there’s another problem:

You can’t just take iron and call it a day because iron has the ability to react with thyroid medication and render it inactive.

So if you take iron without taking it appropriately you can actually reduce thyroid function and cause worsening hypothyroid symptoms. 

How do you correct this problem?

Iron is one of those nutrients that must be taken 4 hours AWAY from any thyroid medication that you are taking (this includes all types). 

You do not need to avoid iron 100% if you have low thyroid function but you should be aware of its impact on your thyroid medication (if you take any). 

And be sure to look at your multivitamin ingredients and other supplement ingredients because you might find iron lurking in there. 

#2. Calcium

Next up is calcium and calcium does something very similar to iron. 

Calcium is another ‘binder’ of thyroid medication. 

While it doesn’t harm your thyroid directly it can absolutely bind to and inactivate thyroid medication (2) if you take them at the same time. 

Calcium is found in all sorts of multivitamins and supplements and it’s often recommended by conventional doctors in women who are suffering from bone loss. 

There’s a good chance you may be taking calcium and not realize that it can negatively impact your thyroid medication. 

Like iron, you must take calcium at least 4 hours away from your thyroid medication. 

The only two ingredients that require this strict 4-hour period are calcium and iron, though, so don’t let other ingredients stress you out too much. 

#3. Biotin

Biotin has a bad reputation among thyroid patients who don’t quite understand how it impacts the thyroid. 

Most people believe that it has some negative impact on the thyroid but they can’t quite define that impact and they don’t completely understand it. 

Let me set the record straight:

Biotin does not have any direct negative impact on thyroid function. 

Let me say that again…

Biotin is not dangerous for your thyroid. 

But it does have an impact on the accuracy of your thyroid lab tests which is why it’s included here. 

Biotin, if taken in high doses, can react with the thyroid testing assay and make it look like you have MORE thyroid hormone in your system than you really do. 

So if you are taking high doses of biotin and then you get your thyroid lab tests drawn and tested, it may look like you are taking a higher dose (3) (even when the opposite is true). 

But remember:

It impacts the lab TEST and not your thyroid FUNCTION. 

The simple solution to the biotin problem is to just avoid taking your biotin dose 2-3 days before you get your labs drawn. 

Problem solved!

Don’t avoid biotin because of this but do use it correctly. 

#4. Iodine

I already know what you are thinking on this one:

“How can you say iodine is dangerous when you recommend using it and even put it in your own supplements!?”. 

I do recommend iodine and I think that most thyroid patients are not getting ENOUGH of it. 

But I also believe that many people misuse iodine by using the incorrect DOSE and by using it without first paying attention to other important nutrient levels. 

And THIS is what causes the issues that people have with iodine. 

Taking high doses of iodine can absolutely be dangerous but you must understand what a “high dose” actually means. 

Small to medium doses of iodine (such as those found in my supplements) within the 50mcg to 200mcg dose are perfectly fine and safe for 99% of people. 

You don’t get into trouble until you start using doses higher than 12.5mg per day. 

Sometimes these doses even go all the way up to 50mg per day. 

Once you get into these high doses you start to increase your chance of developing autoimmune thyroiditis, Hashimoto’s, and even Graves’ disease. 

The bottom line?

Use iodine but don’t use excessively high doses as they are increasingly dangerous without any increase in benefit compared to lower doses. 

If you stick to any of my supplements here you should be good to go because they are formulated with all of this information in mind. 

#5. Thyroid Glandulars

I’ve been critical of thyroid glandulars in the past and now I want to walk back my previous statements with a bit of added caution. 

If you aren’t aware of thyroid glandulars let me fill you in: 

Thyroid glandulars are portions of animal thyroid glands that have been dried and crushed and added to over-the-counter supplements. 

This should sound very familiar to you, especially if you take any medication that falls into the natural desiccated thyroid camp. 

Because this is nearly identical to the way that NDT medications such as Armour Thyroid and Adthyza are created. 

There’s one big difference, though: 

Thyroid glandulars are not supposed to contain any active thyroid hormone (such as T4 or T3) whereas NDT is supposed to contain these hormones. 

But the problem with some thyroid glandulars is that they do contain some amount of thyroid hormones and this is why they can be dangerous. 

You never want to take any supplement that may contain active thyroid hormones as they will be inconsistent in their dose and they WILL interfere with your ability to interpret your thyroid lab tests. 

This is why thyroid glandulars make this particular list. 

But are glandulars dangerous if they do not contain thyroid hormones?

This is where I’ve changed my mind. 

I used to think they didn’t have a place in thyroid treatment and management but I’ve since changed my mind after I’ve been using them more recently. 

As long as your thyroid glandulars come from a reliable source AND they do not contain any active thyroid hormones they can be very helpful for thyroid function. 

They are especially helpful in those people who don’t have a thyroid gland because of thyroid surgery, in those post radioactive iodine ablation, and in those who have end-stage Hashimoto’s. 

#6. Fiber

When most people think about fiber they probably think about foods high in fiber but there are also supplements that are high in fiber as well. 

These include things like Metamucil, Citrucel, Benefiber, and so on. 

All of these are over-the-counter supplements that contain massive amounts of fiber. 

I’m not going to get into whether or not fiber is healthy for you here but you should know that fiber CAN impact your thyroid. 

It impacts your thyroid because it can SLOW down the absorption of your thyroid medication if you use your fiber supplement around the same time of day as your thyroid medication. 

If you are taking a fiber supplement (of any type) just be sure to take it AWAY from your thyroid medication. 

Because there’s really no reason to take your fiber supplement at the same time of day as your thyroid medication you should separate them out and take one in the morning or one in the evening (if you even use a fiber supplement, that is). 

#7. Caffeine

Next on the list is caffeine. 

And let me take the unpopular position here and just say that if you have thyroid disease of any type then you should be avoiding caffeine 100%. 

This includes all sources of caffeine including coffee (which has a negative impact on your thyroid by itself (4)), energy drinks, sodas, and any other source of caffeine. 

Why do you need to avoid it?

For several reasons: 

The first is that caffeine by itself has a stimulatory effect on your intestinal tract. 

The more caffeine you take the faster your intestinal tract will move and the less time your thyroid medication has to be absorbed. 

Caffeine will almost always reduce the absorption of your thyroid medication if it’s taken anywhere near your thyroid medication (again, including all types of thyroid medication). 

But there’s another reason…

Caffeine also has a stimulatory effect on your adrenal function and virtually every person with low thyroid also suffers from adrenal problems (to some degree). 

So caffeine not only negatively impacts the absorption of your thyroid medication, but it can also negatively impact your adrenals which WILL impact your thyroid function. 

Do your best to stay away from caffeine from all sources, especially caffeine supplements or pre-workout supplements that contain very high doses of caffeine. 

#8. Acid Blockers

I’ve included acid blockers here even though they are technically an over-the-counter medication and not a supplement. 

They could be considered a supplement because they are so easy to purchase (they can be bought at most box office stores) and people use them so often that they might as well be considered supplements. 

It turns out that while acid blockers are terrible for your general health, they are also terrible for your thyroid. 

Acid blockers work by reducing the amount of acid that your stomach can produce. 

This may reduce the symptoms of acid reflux but it comes at the cost of reducing virtually every other nutrient that you need to absorb in your intestinal tract. 

It also reduces the absorption of medications and supplements, leads to nutrient deficiencies, and disrupts your gut microbiome. 

If you have thyroid disease you do NOT want to take acid blockers for conditions such as acid reflux. 

It will worsen your thyroid function directly and lead to nutrient deficiencies that will further harm your thyroid (such as iron, B12, and magnesium deficiencies). 

#9. Estrogen Enhancing Supplements

Estrogen is obviously a good thing and something that you want to have an adequate amount of in your body. 

But you can get into trouble if you take supplements or medications that either enhance estrogen levels or directly provide your body with estrogen. 

Estrogen has a stimulatory effect on something known as thyroid-binding globulin (5). 

Thyroid-binding globulin is the protein that holds and carries thyroid hormone in your bloodstream. 

If you have high levels of thyroid-binding globulin then there is a limited amount of thyroid which can interact with your cells thus changing the state of thyroid hormone. 

Estrogen supplements are not bad or harmful but you should be aware of the impact that they have on thyroid hormone metabolism. 

If you take these supplements you need to account for them when you adjust or interpret your thyroid lab tests. 

If you don’t then you may not make the appropriate adjustments to your thyroid medication. 

Final Thoughts

Taking supplements if you have thyroid disease (of any type but especially hypothyroidism or low thyroid function) can be incredibly helpful!

Just realize that not all supplements are “good” and that those who have thyroid problems are in a unique circumstance compared to other people. 

You also can’t, and shouldn’t, count on your doctor to know these things!

Most doctors are barely aware of the biotin issue I mentioned above (even though it can seriously impact the accuracy of your lab tests) and only a handful are aware of just how strong of an impact things like calcium and iron have on your thyroid medication. 

This means it’s up to YOU to be aware of these things!

Now I want to hear from you:

Were you aware of these supplements and how they impact your thyroid?

Are you taking any of these supplements or nutrients already?

Are you planning to change how you take them?

Or do you have any other suggestions to add based on your own experience?

Leave your questions or comments below!