How to Test for T2 Thyroid Hormone

How to Test for T2 Thyroid Hormone

T2 thyroid hormone is emerging as an incredibly important and potent thyroid hormone. 

And tons and tons of thyroid patients are taking notice. 

This has led many a thyroid patient to ask themselves an important question: 

“How can I test my own T2 level to see if I should take it?”. 

If this thought has crossed your mind then you are in the right place. 

Let’s talk more about T2 testing, why T2 thyroid hormone is so beneficial to thyroid patients, and how to determine if you should try it: 


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Can You Test For T2 Thyroid Hormone? 

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Let’s start with the bad news: 

Currently, there is no commercially available T2 test for thyroid patients. 

This means that, unfortunately, you aren’t going to be able to test your T2 level like you would your free T3 or free T4

This doesn’t mean that you can’t make highly educated guesses about your T2 status (which we will talk about below). 

And it definitely doesn’t mean that there are no T2 tests period, it just means that they aren’t readily available for you and me. 

This is for a couple of reasons: 

The first is that the available tests are not quite as accurate as we’d like. 

There are many different ways that researchers can assess T2 status for research purposes, but many of them fail to provide accurate results because they aren’t sufficiently accurate when T2 levels are low (1). 

Some of these T2 tests miss up to 1/3 of patients with low T2 levels. 

The second is that we are still learning about T2, its functions in the cell and on thyroid hormone receptors, and how it is bound and carried through the body. 

This information is well known for thyroid hormones like T3 and T4 which is why we have tests like free T3, free T4, total T3, and reverse T3

Researchers better understand the lifecycle of these hormones, how they are carried through the blood, and how they interact with thyroid hormone receptors. 

While we do know that T2 exerts powerful effects on many different systems in the body, and interacts with the thyroid hormone receptor (2), there’s still a lot left to learn. 

Just because you can’t test for your T2 level like you would, let’s say, your T3 level, doesn’t mean that you can’t estimate how much T2 is in your body or if you would benefit from taking a T2 supplement. 

So, at least for now, educated guessing is the only way to tell if you would likely benefit from taking T2. 

I understand that for many thyroid patients, this isn’t the ideal situation, but the only alternative is to just avoid T2 until commercial testing is available which may take several years.

But if you don’t like the idea of sitting and waiting while these tests are developed, then here are some ways that you can estimate your T2 status. 

Proxy Measurements To Tell if You Need More T2

These tests are what I call proxy measurements and while it would be preferred to have a true T2 test available, these measurements can still give you a lot of information about your thyroid status. 

Here’s how they work: 

While we may not have a good way to assess T2 levels in the body, we have a pretty good idea of how T2 functions

So what we can do is look at the systems that T2 impacts to see if it’s doing what it should be doing. 

If it isn’t, then we can make an educated guess that there is probably not enough T2 in the system. 

And this method of evaluating thyroid hormone shouldn’t be surprising to many of you because it’s something that we often do for evaluating T4 and T3 levels. 

If you are taking a thyroid medication like levothyroxine and still experiencing symptoms like weight gain or hair loss, then you can make an educated guess that you probably aren’t getting enough of it. 

The primary difference here is that you’d be able to confirm your suspicions with thyroid lab tests, which is not something we can do, but we can still do the first part. 

How accurate is this method of looking at proxy measurements? 

Based on my experience, they are fairly accurate. 

I say that because I’ve had the advantage of monitoring and interacting with thousands of people who have used my own T2 supplement and we rarely ever see problems using this method. 

With this in mind, let’s talk about these proxy measurements: 

#1. Resting Heart Rate

The first is a simple metric that you can test at home right now. 

Here’s how it works:

Your heart contains thyroid hormone receptors (3) which are known to be sensitive to T2 thyroid hormone. 

We know this because excessively high doses of T2 (not the type of dose you would find in a supplement) can cause cardiac enlargement (4). 

This enlargement doesn’t happen with normal doses, but the fact that it happens with high doses tells us that T2 has some impact on the heart. 

In the hypothyroid T2 deficient state, we would expect that the heart rate would decline to a low level and this is exactly what we see in many thyroid patients

Just using this measurement alone can be tricky, though, because we also know that T3 thyroid hormone acts on the heart as well. 

So if you are a thyroid patient taking levothyroxine (which contains T4) and experiencing a low resting heart rate, how do you know if your problem is with T3 or T2?

Well, the most obvious way to tell the difference is with testing. 

You can’t test for T2, but you can definitely test for T3. 

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If you have a low resting heart rate AND you are taking levothyroxine AND your free T3 is relatively normal then, by process of elimination, only T2 thyroid hormone is left. 

And in this situation, it would be a very reasonable idea to try T2 supplementation. 

One of the best things about this measurement is that it’s so easy to test for

All you need to do is find your pulse, count for 15 seconds, and then multiply that number by 4 to give you your resting heart rate. 

For best results, make sure you check your pulse first thing in the morning. 

Alternatively, if you don’t want to do the manual method, you can also use a wearable device like an Apple watch or Fitbit. 

A normal resting heart rate is somewhere between 60 to 80 beats per minute. 

When you are in a hypothyroid state, you may find that your resting heart rate is in the 50 beats per minute range which would be highly indicative that your heart is not getting enough thyroid hormone (T3 or T2). 

From here it’s just a matter of experimenting with T2 to see if you can bring that resting heart rate back up and better control your other thyroid symptoms. 

#2. Metabolism

The second proxy measurement you can look at is your metabolism. 

As far as thyroid hormones go, T2 is a major regulator of metabolism and it may even be more important in this regard than T3. 

Right now there’s a lot of effort and research evaluating T2 as a potential weight loss therapy (5), but this research is still ongoing. 

When thyroid hormones are low (both T2 and T3), your metabolism will drop in response. 

This is likely due to the impact that these hormones have on hypothalamic function, mitochondrial energy production, and leptin signaling (6). 

Either way, a sluggish or low metabolism is a potential sign of a hypothyroid T2 deficient state. 

Much like the example above, T3 also plays a role in regulating your metabolism so having a sluggish metabolism doesn’t automatically mean you have low T2. 

But, again, just like the example above, you can differentiate between T3-related low metabolism and T2-related low metabolism with testing. 

If your metabolism is low and your T3 is fine then it’s likely that T2 is playing some role. 

Testing your metabolism is actually quite difficult so instead of trying to assess how many calories you are burning on a daily basis, it’s best to look at your weight and your ability to lose weight as a proxy measurement of basal metabolic rate.

Most of us have a pretty good idea whether or not our bodies are responding to weight loss treatments the way that they should. 

If you are having a hard time losing weight despite regular exercise and healthy eating or if you are noticing that you continue to gain weight despite eating fewer calories than normal, then it’s likely you have an issue with your metabolism. 

In this setting, a trial of T2 supplementation would be very reasonable. 

#3. Cholesterol 

In addition to testing your resting heart rate and metabolism, you can also look at your cholesterol level as a proxy measurement of your T2 status. 

Your thyroid is a known regulator of your cholesterol and when thyroid function is low, you will see your cholesterol rise

The low thyroid state is associated with a high LDL, high triglycerides, high total cholesterol, and a low HDL. 

This cholesterol pattern is typical in those who suffer from insulin resistance and obesity which means it’s not a great marker by itself. 

However, there’s a lot of interest in using T2 and T2 analogs for their beneficial effects on cholesterol metabolism and as a potential treatment for fatty liver (7). 

As someone with thyroid problems, if you notice that your cholesterol is generally high and unresponsive to thyroid medications then you may want to try additional T2 to help normalize those levels. 

This marker isn’t perfect, though, because there are plenty of other factors that can impact your cholesterol panel. 

#4. T3 and T4 Levels

You can also attempt to assess your need for T2 based on your other thyroid hormone levels. 

The reason this strategy may work has to do with how your body metabolizes and breaks down thyroid hormones. 

It’s understood that thyroid hormones, starting with T4, get metabolized by deiodinase enzymes by taking off iodine molecules. 

If you remove 1 iodine molecule from T4 you’re left with T3. 

If you remove 1 iodine molecule from T3 you’re left with T2. 

And if you remove 1 iodine molecule from T2 you’re left with T1. 

So one way that you can attempt to assess your T2 status is by looking at T4 and T3 levels. 

If we know that your body creates T2 from T3 then if you are low in T3 you probably won’t be able to make very much T2. 

The same logic applies when looking at T3 status. 

If the majority of T3 in your body is created by T4 to T3 conversion then your T4 status is important for your T3 level. 

While this makes sense logically, it’s probably not as straightforward as I’ve made it sound. 

Some studies indicate that T2 status remains unchanged regardless of T3 levels (8). 

This is further complicated by the fact that there are multiple T2 metabolites and that T4 can also be converted into reverse T3. 

How reverse T3 impacts T2 levels is not known, at least at this time. 

Even with all of this uncertainty, it’s been my experience that having low T4 or low T3 is a fairly good predictor that someone will do well when taking T2. 

This is probably because T2 acts as a ligand on the thyroid hormone receptor making it more sensitive to circulating T3 levels. 

Again, we are still figuring all of this out but this is the best information I can give right now. 

#5. Thyroid Symptoms

Finally, you can also use your thyroid symptoms to help determine if you would benefit from additional T2. 

This is probably the most obvious out of all metrics and the one that everyone should understand the best. 

If you have a thyroid condition and you are experiencing persistent thyroid symptoms then there’s a good chance you probably need more thyroid hormone. 

This is probably because most thyroid patients are being treated with one thyroid hormone in the form of levothyroxine. 

The regulation of thyroid hormone in your body and in your cells is very complex and yet most doctors treat this problem with one thyroid hormone. 

It’s very likely that each thyroid hormone plays some role in the regulation of thyroid hormones including T4, T3, T2, and T1. 

So, if given the chance, and if you want to try and replicate the function of a healthy thyroid gland, it makes sense to replace as many of these hormones as possible. 

This is probably why so many patients prefer thyroid medications like Armour Thyroid.

Just because we don’t completely understand the function of all of these hormones doesn’t mean they aren’t important. 

For this reason, it makes sense for most thyroid patients, especially those who are having trouble managing their symptoms, to try T2 supplementation. 

Recap and Final Thoughts

If you ask me, I think it’s very likely that we will see a commercially available test for T2 thyroid hormone in the coming years. 

And within the next 10 years, I think that T2 testing will become part of the standard thyroid panel, that T2 thyroid hormone will make its way into several thyroid medications (think combination T4 + T2 medications), and that ultimately doctors will recognize the importance of all thyroid hormones. 

If you don’t want to wait 5-10 years for this to happen, you can always get started taking T2 thyroid hormone right away. 

And if you do decide to go that route, make sure you are at least keeping an eye on the proxy measurements that I’ve mentioned above. 

Just like T4 or T3, you don’t want to take more of any thyroid hormone than what your body needs. 

Now I want to hear from you:

Were you aware of T2 thyroid hormone before reading this? Or is this your first time hearing about T2? 

Have you thought about using T2 before? Did the fact that you can’t test for it stop you? 

What do you think your personal T2 status is? Do you think you should try a T2 supplement?

Leave your questions or comments below! 

Scientific References









how to tell if you need t2 thyroid hormone

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

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14 thoughts on “How to Test for T2 Thyroid Hormone”

  1. Hi do you have a resource for appropriate dosing for total thyrodectomy patients? Literature has left me with insufficient doses if my t4/t3 combo therapy and I need guidance on better dosing. Thanks!

  2. Hi. I’m 62 and have been taking levothyroxine for about 25 years. Constantly having to swap dosage between 125 and 150mg. I’ve gone from 8st to 11st and now on my way to 12st and my cholesterol has risen a lot. Been on numerous NHS weight loss courses and nothing is wrong with my diet and amount of exercise I do. Can I try T2 without it affecting my normal test. Thanks.

    • Hi Gwen,

      Based on what we know, T1 doesn’t seem to be super important. But that’s what they used to think about T2, so that may change as more research is done.

  3. What about T2 levels when a person is only on T3? FT4 and TSH are zero when FT3 is optimal, and since you indicate the body makes T2 from T3, a person with optimal FT3 levels should be making enough T2, correct? What if an optimal T3-only person still can’t lose weight despite being on an 80/20 carnivore diet (fasting glucose still over 100, ketones still low)? Is there a genetic variant that impacts T3 to T2 conversion similar to the DIO variants that impact T4 to T3 conversion?

    • Hi Aimee,

      That is not correct for the same reason it’s not correct to assume someone can make enough T3 if they have enough T4. That would be true, provided everyone had the same genetics, the same enzyme function, and no other medical conditions, but that’s certainly not the case so I would not automatically assume if T3 levels are sufficient that your T2 is optimal.

    • Hi Vickie,

      Absolutely. People theorize that NDT contains T2 because of its source but I’ve never seen any documentation to prove that it’s actually in there. Even if it were, though, it’s not standardized, the dosing is unknown, it would be insufficient as most T2 is in the peripheral tissues (not the thyroid gland), and would vary from lot to lot.

      For these reasons, you can’t count on NP Thyroid or any other form of NDT as a consistent dose of T2.


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