If we are talking raw power, some of the best thyroid supplements for your money would be those that help your body convert T4 into T3.
Why?
Because T3 is the most powerful thyroid hormone and it’s the hormone that most thyroid patients don’t have enough of.
But you can increase how much your body is capable of producing naturally by taking the right supplements.
And these supplements work no matter what type of low thyroid problem that you have.
In fact, your thyroid can even be removed and they still work because this conversion process occurs outside of the thyroid gland.
So, should you take them? I think so and let me explain why:
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1. They Can Increase Free T3 Levels
Free T3 is the measure of the most active thyroid hormone in your entire body.
The more free T3 that you have, the better you will feel.
And if we are looking at thyroid patients across the board, most of them simply don’t have enough T3.
Sure, they are taking thyroid medications like levothyroxine but this medication will do nothing unless your body actively converts it into T3 (which we will talk about in a second).
For many people, increasing free T3 is truly the missing piece to helping them feel better.
It’s also the reason that they may feel terrible despite having normal labs.
Because you can have a normal TSH and even a normal T4, but that won’t help you feel better if your T3 is low.
2. They Can Help Reduce Thyroid-Related Symptoms
Another huge benefit, and probably the reason that most people take these types of supplements is because they impact how you feel.
Many thyroid patients focus on all of the wrong things and none of the right ones.
For instance, they will focus on their lab tests while ignoring their symptoms.
But who cares what your labs show on paper if you feel terrible?
This is where T4 to T3 conversion supplements step in.
By supporting T3 levels, even at the cellular level and even if they have no impact on your free T3, you can take control of some of the most discouraging symptoms that thyroid patients like:
- Persistent fatigue
- Weight gain or difficulty losing weight
- Brain fog
- Hair loss
- Sensitivity to cold
- Hair loss
- And a sluggish metabolism
All of these stem from a lack of thyroid function, specifically T3, at the cellular level.
The more support you provide to your cells, the more likely you are to see a reduction in these symptoms.
And, at the end of the day, that’s really what matters. Getting back to feeling like your old self.
3. They Support Thyroid Medication Function
There’s a big problem with the most commonly prescribed thyroid medications like levothyroxine and Synthroid:
They only contain T4.
This means your body has no use for them unless they can be activated and turned into T3.
But we know, based on genetics and other factors (1), that not every single thyroid patient is able to manage this conversion process.

And if you are one of the unlucky few who can’t, you’re going to feel it.
This is where thyroid conversion supplements step in:
They help your thyroid do its job by helping your body to activate them and turn them into T3.
The result is better thyroid function, more efficient use of thyroid medication, and fewer thyroid-related symptoms.
Ingredients That Help Your Body Convert T4 Into T3
Whether or not your conversion supplement will work has everything to do with its ingredient profile.
But let me be blunt:
Not every thyroid conversion supplement is created equal.
And because thyroid conditions have become somewhat trendy as of late, there are a lot of bad products on the market that walk around masquerading as conversion supplements when they are anything but.
I’m not going to name and blame here but instead, provide you with the information you need to know to make sure you’re taking the right ingredients.
Here’s a list of ingredients that can help your body convert more T4 into T3:
- Zinc: Many thyroid patients are deficient in this essential mineral which is used by the very enzymes that convert T4 into T3 (2). If you are deficient in zinc, your body will have a hard time creating T3. End of story. And because sub-optimal zinc levels exist in many thyroid patients, taking zinc is a good idea. But how much you take and in what form matters. For best results, use 5-15mg per serving of zinc glycinate, zinc amino acid chelate, or zinc citrate.
- Selenium: Much like zinc, selenium is another powerhouse nutrient that supports deiodinase enzymes which are needed to convert T4 into T3. In addition, selenium provides protection to your thyroid against oxidative stress (3) by supporting glutathione production. So it’s also a no-brainer if you have low T3. For best results, take 75 to 150 mcg of selenium each day as selenomethionine, selenium glycinate complex, or selenocysteine. But do not exceed this threshold because you can easily overdose on selenium if you aren’t careful.
- Guggul Extract: Guggul extract is a naturally occurring resin that enhances the enzymes that convert T4 into T3 (4). It also has anti-inflammatory, cholesterol-lowering, and metabolism-supporting properties making it great for thyroid patients.
- Ashwagandha: This adaptogenic herb supports T3 levels indirectly by reducing stress (5), which negatively impacts T4 to T3 conversion.
- Vitamin A: While not directly involved in the conversion process, vitamin A helps your T3 work more effectively at the cellular level by supporting its binding to the nuclear receptor (6). So while you may not need it for T4 conversion per se, it’s still a great complementary nutrient to take along with the other listed here, especially since most thyroid patients don’t get enough from their diet.
How to Tell If You Need to Support T4 to T3 Conversion
Many thyroid patients overthink this but it’s actually quite simple.
Whether or not you need thyroid conversion support depends on two factors:
- The first? Your Lab Tests: If your free T3, total T3, or even free T3 level is low, there’s a good chance you would benefit from taking them. The T3 lab tests make sense, but why free T4? Well, because your body uses T4 to create T3, so if your T4 is low then we know your body is not going to have enough substrate to create the T3 it needs. Don’t worry about your other lab tests, just focus on these.
- The second? Your Symptoms: The reality is if you still have low thyroid symptoms despite taking thyroid medication, regardless of what your labs show, you are hypothyroid. Period. So when in doubt, focus more on your symptoms than on your lab tests (they are also much easier to test).
When in doubt, it’s safe to assume that you probably have a conversion problem and would benefit from taking these ingredients.
I can say this after having helped thousands and thousands of thyroid patients over the years.
The Bottom Line
T4 to T3 conversion supplements are a game-changer for many thyroid patients, especially those who have struggled to feel better on conventional medications like levothyroxine.
But managing these symptoms is as easy as ensuring your body has what it needs to create more T3.
And doing that is as easy as taking the right supplement.
I’ve already done the leg work and research needed to put all of the most bioavailable ingredients in the correct forms and at the correct doses in my T4 to T3 conversion supplement.
So if you want the easy route, you can just take that.
If you prefer to piece together your own ingredients, one by one, you can do that as well.
But no matter what you decide to do, just make sure you do something.
By the way, did you know that there are other ways to naturally increase free T3? You can find a list of those treatments here.
Scientific References
#1. https://pmc.ncbi.nlm.nih.gov/articles/PMC9544560/
#2. https://pubmed.ncbi.nlm.nih.gov/30982439/
#3. https://pubmed.ncbi.nlm.nih.gov/26854239/
#4. https://pubmed.ncbi.nlm.nih.gov/15798994/
#5. https://pubmed.ncbi.nlm.nih.gov/28829155/
#6. https://pmc.ncbi.nlm.nih.gov/articles/PMC9592814/
