The Worst Supplements To Take For Your Thyroid (Avoid These!)

The Worst Supplements To Take For Your Thyroid (Avoid These!)

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The right supplements can dramatically improve your thyroid symptoms and help your thyroid function in an optimal way. 

Using the wrong type or form of supplements will leave you with zero benefits and money left in the toilet…

But that’s not going to be a problem for you because you are reading this blog post!

Today we are going to be discussing the WORST supplements that you can take for your thyroid and what you should be using instead. 

And believe me, when I say, you’re probably taking several of these supplements without even realizing it. 

If you are, leave a comment below and let me know!

Let’s jump in: 

Avoid These Supplements (& Forms) If You Want To Support Your Thyroid

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First, here’s a quick disclaimer: 

I’m a huge fan of using supplements to support your thyroid as many of you probably already know. 

While I always advocate trying to get as many nutrients as possible from food, supplements often make sense, especially for thyroid patients

If you can get away without the need for supplements, more power to you. 

But if you are trying to augment your existing regimen, then you should find this information very helpful. 

I’ve found that many thyroid patients, simply due to a lack of knowledge, shop for supplements based on pricing. 

This results in poor-quality supplements that may end up doing more harm than good as you will soon find out. 


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#1. Magnesium Oxide. 

First on the list is magnesium oxide. 

Don’t get confused here because I’m not saying that magnesium is bad for the thyroid, I’m saying that magnesium oxide is the worst FORM of magnesium you can take for your thyroid. 

There’s a big difference. 

Magnesium is actually a great supplement for supporting thyroid health. 

It’s required for multiple functions that all help your thyroid including:

When you couple these benefits with the fact that so many thyroid patients are deficient in magnesium, it’s a no-brainer to supplement with it. 

The big problem is that the most commonly used form of magnesium is also the least effective form. 

And that form is magnesium oxide. 

I just did a video on the various forms of magnesium available so check that out below if you want even more information!

Magnesium oxide is a decent option if you want to treat something like constipation but it’s a terrible one if you are trying to get magnesium into your body for thyroid support. 

So what should you actually be taking? 

For thyroid support, I would recommend using magnesium glycinate

Magnesium glycinate is much better absorbed and only slightly more expensive than magnesium oxide making it a clear winner for thyroid patients. 

This is why you’ll only find magnesium glycinate or magnesium citrate in the supplements that I formulate

I didn’t mention magnesium citrate here, but in the video above I explain why that’s also a great form for thyroid patients. 

If you are currently taking a magnesium supplement then I would recommend checking the supplement fact panel on the back to see what form you are taking. 

On the back, it will state something like magnesium as magnesium “x”. 

If you find magnesium oxide on the ingredient list, especially in your thyroid support supplement, then you know that the manufacturer of this supplement has no idea what they are doing. 

This is because magnesium oxide is the worst form you could possibly recommend for thyroid patients. 

As a general rule to avoid problems like this in the future, don’t purchase supplements based solely on price but instead on a combination of price and ingredient forms and doses!

The reason you can find some supplements so cheap is because they use these forms but the reality is hardly any of those ingredients are actually making it into your body so you are wasting money. 

#2. Zinc Oxide. 

Just for clarity here, I’m not saying zinc is bad for your thyroid, I’m saying zinc OXIDE is bad for your thyroid. 

Zinc by itself is GREAT for thyroid support which is why many thyroid patients want to take it. 

Your thyroid needs zinc for T4 to t3 conversion (4), the binding of thyroid hormone to the nuclear receptor, and for the production of TRH

And because many thyroid patients are not getting enough zinc, and because it can be difficult to meet your zinc demands using diet alone, zinc supplements make a lot of sense. 

The only problem is that zinc oxide won’t help you replace low zinc levels nor will it support thyroid function.

And just like magnesium oxide, it’s the worst form of zinc you could use to support your thyroid. 

The fact that it’s poorly absorbed is only part of the problem. 

The other part is that the poor absorption necessitates higher doses which leads to major nausea and stomach pain when taken. 

These symptoms are the #1 reason that thyroid patients don’t take zinc! 

What’s crazy is that you can get by with a MUCH smaller dose when using slightly more expensive forms of zinc like zinc glycinate or zinc citrate (5). 

These forms are better absorbed which means you need much less of them which means you won’t experience any negative symptoms when you take them. 

join 80,000 other thyroid patients who have used dr. westin childs' thyroid support supplements.

If you are taking a thyroid support supplement make sure you check the ingredient list to see what type of zinc you are actually taking. 

If no specific form of zinc is mentioned then you can bet your bottom dollar that the quality of that supplement is dubious. 

Because it indicates that the manufacturer is either oblivious to the fact that zinc comes in different forms (which is obviously not ideal) or, worse, they are trying to be deceptive. 

#3. High-Dose Iodine. 

You didn’t think we could get through a supplement list without at least mentioning one of the most controversial ones, did you?

Well, here we are!

And when I talk about high-dose iodine, I’m really talking about doses higher than 1mg or 1,000 mcg.

For context, the RDA for iodine is around 150 to 300 mcg so this dosing is roughly 3x that of the RDA. 

Many people wouldn’t even consider 1,000 mcg of iodine to be a high dose because those same people often recommended doses as high as 50 mg or 50,000 mcg per day. 

I’ve been clear that these types of doses should be avoided for the majority of thyroid patients because once you get above the 1mg or 1,000 mcg threshold, the risks simply don’t outweigh the potential rewards. 

Consistent use of high-dose iodine has been well-documented to trigger autoimmune thyroid diseases like Hashimoto’s and Graves’ (6). 

In other words, it CAUSES thyroid problems. 

Proponents of high-dose iodine will tell you that this connection isn’t real or that it’s safe because the Japanese population consumes that much iodine without any problems. 

But both of these statements are false. 

There’s absolutely a connection between iodine intake and autoimmune thyroid disease that occurs in a U shape pattern. 

Below the 150 to 300 mcg level you see thyroid problems increase and as you approach the 150 to 300 mcg level you see those same problems decrease and then you see them increase again once you go over 300 mcg. 

But even if this weren’t the case, we know that the Japanese don’t consume anywhere near the doses that people say. 

Recent estimates suggest that they consume closer to 1 to 3 mg (which is 1,000 to 3,000 mcg) of iodine per day.

This is significantly less than even the lowest of high-dose iodine recommendations which typically start at 12.5 mg/day or 12,500 mcg/day. 

The Japanese definitely consume more iodine on average than people in the United States (which is mostly my audience here) but their lifestyle and other food choices are completely different. 

So you can’t really directly compare their iodine intake and health outcomes to people in the United States or other countries for that matter. 

The bottom line?

Stick to iodine doses in the range of 150 to 300 mcg and you won’t have anything to worry about any of this. 

#4. Cyanocobalamin. 

Cyanocobalamin is an artificial and synthetic form of vitamin B12 and it has 2 big problems:

The first is that it requires activation by the body before it can be used. 

So forget about the fact that it’s artificial, which is not ideal by itself, it also requires energy to be activated. 

And there are some common genetic mutations that interfere with this activation process. 

Those with the MTHFR genetic mutation struggle to convert this form of B12 into the active and usable form. 

That’s problem #1, problem #2 is that cyanocobalamin comes bound to a compound called cyanide. 

Yes, cyanide is toxic to humans, but the amount you get from the breakdown of cyanocobalamin isn’t enough to cause toxicity by itself.  

Having said that, the cyanide component still MUST be eliminated by the body which requires extra effort and work. 

In addition to being potentially toxic, cyanide also acts as a goitrogen when it is metabolized into a breakdown product called thiocyanate (7). 

Despite all of this, some people still try to suggest that cyanocobalamin is fine and safe to use. 

I’m not saying it’s necessarily harmful, but why on earth would you take an artificial and synthetic form of b12 that is 1) difficult for a huge portion of the population to utilize and 2) that can potentially cause thyroid problems during its metabolism? Especially when there are better and cleaner options available. 

I’ll let you decide which option you prefer but I know which one I’m sticking with. 

If you want to use a quality form of vitamin b12 then stick to methylcobalamin, adenosylcobalamin, or hydroxycobalamin

#5. Vitamin D2. 

Notice I said D2 here and not D3. 

Improving your vitamin D level is incredibly beneficial for general thyroid health but what you need to understand is that not all forms of vitamin D supplements do this equally well. 

Vitamin D2 is known as ergocalciferol and vitamin D3 is known as cholecalciferol. 

Vitamin D2 is primarily found in plants whereas vitamin D3 is primarily found in animals. 

Vitamin D2 is cheaper to manufacture so it’s the vitamin D that is frequently used to fortify foods like milk (8). 

Vitamin D3 is the preferred form because it provides more effective at increasing vitamin D levels (9) in the serum when taken. 

There are also more studies highlighting its effectiveness over vitamin D2. 

Outside of fortified foods and injections from doctors, I don’t see vitamin D2 being used that often but just double-check your supplements to make sure you aren’t taking this form. 

The ideal vitamin D choice is vitamin D3 somewhere around 1,000 to 10,000 IUs per day depending on your sunlight exposure. 

Final Thoughts

Guys, the bottom line is that it comes down to quality. 

Yes, some of the alternative formulations that I’ve mentioned above are more expensive than the section highlights but, at the end of the day, we are talking about your health. 

I think it’s worth paying a little extra to get quality ingredients that you know will actually have a positive impact on your health and on your thyroid. 

If you are using any of my supplements then, naturally, this is all taken into account so you don’t need to worry about it. 

And if you just want to see what a quality formulation looks like, you can see all of my thyroid support supplements here

Even if you don’t end up using them, you should at least use them as a guide to understand what you should be taking. 

Now I want to hear from you:

Be honest, are you taking any of the supplements that I’ve listed above?

Were you aware that there are different forms of various supplements available? 

Are you planning on making any changes to your supplement regimen after reading this?

Leave your questions or comments below! 

Scientific References










these supplements make your thyroid worse

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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.

P.S. Here are 4 ways you can get more help right now:

#1. Get my free thyroid downloads, resources, and PDFs here.

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#4. Follow me on Youtube, Facebook, TikTok, and Instagram for up-to-date thyroid tips, tricks, videos, and more.

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