How to use The Total T3 Lab Test to Help Evaluate your Thyroid

Total T3 is one of many thyroid lab tests but it's one that not many patients are aware of. 

I've been successfully using total T3 in many patients and I feel that it is an invaluable tool to help you completely understand how your body is utilizing thyroid hormone. 

Article highlights:

  • Total T3 is a measurement of both free and bound T3 in your body. 
  • T3 is the single most important thyroid lab test you can order because T3 is the most important thyroid hormone. 
  • Optimizing your T3 may help you feel better, lose weight, and reduce your symptoms of hypothyroidism.
  • You should optimize your total T3 to the top 30% of the reference range but be cautious of making it go higher.

More...

What Exactly is Total T3?

Before we jump in let me provide some quick information. 

All of my articles contain links to clinical studies which help provide further information on the claims that I make in my articles. 

Unfortunately, there just isn't a lot of research when it comes to total T3. 

Much of this has to do with the current thyroid treatment paradigm which focuses on other lab tests such as the TSH and the free T4. 

There are more studies on those topics than on T3, especially total T3. 

With that in mind, I'm going to focus on how I look at this particular test and how why I believe that it has value to you as an individual.

Most of the information I will be presenting here is based on my own personal experience in using this lab test and in helping treat many patients. 

So, back to our regular discussion. 

What exactly is total T3?

Total T3 is a simple thyroid lab test (one of many, by the way), which is used to give you information on how much T3 thyroid hormone is in your bloodstream. 

The idea is that the more T3 available, the more likely your thyroid is to work. 

This simple logic is why every single thyroid patient should have their thyroid hormone levels tested in addition to testing the TSH!

Do not neglect these tests. 

Total T3, along with free T3, is perhaps the single most important thyroid tests that you can order because they give you the most information about your thyroid. 

Even if you don't know much about your thyroid you should remember this:

T3 is the most biologically active thyroid hormone in your body. 

Why?

Because T3 is the main way that thyroid hormone influences your cells and turns on the right genes. 

If you don't have sufficient T3 in your body (total or free) you will simply not feel well. 

There's much more to this concept, but I want to keep it brief for purposes of this discussion. 

If you want to dive into more detail you can find more information on free T4 here and TSH here which will help you understand how these lab tests fit into the greater picture. 

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. 

How to Calculate "Optimal" Free T4, Free T3, & Reverse T3 Ratio: 

Calculating these ratios is important because it can help you determine if your efforts are on the right track and whether or not your medications are working. 

Download more free resources on this page

Free T3 vs Total T3

Total T3 is a completely different test and should be differentiated from free T3. 

Both tests are important, but each test gives you different (but useful) information. 

Often times, doctors put more emphasis on the concentration of free hormones when compared to the total concentration of hormones. 

Why is this?

Because we know, and this is true for total T3, that the free component of any hormone is much more active (1) compared to the bound or "total" concentration of protein in the body. 

Thyroid hormone circulates through your body in one of two ways:

#1. Bound to proteins which act to stabilize and prevent the decay of thyroid hormone.

And #2. Free and unbound are available to be used by the body at a moments notice. 

Your body uses this system to help prevent the unnecessary use of thyroid hormone and to save it for the tissues that really need it. 

If all of your hormone was free and active then your body would have a hard time saving it for certain tissues. 

So, instead, your body binds up 99% of the thyroid hormone (2) in your blood and only leaves a small fraction, less than 1% (0.04% to be exact (3)), free and active. 

In this way, your body creates a system which is in equilibrium. 

When you test your free T3 you are testing for the incredibly small, but incredibly active, amount of thyroid hormone in your body. 

Your total T3, on the other hand, represents both the free and total amount and gives you a bigger picture as to what is happening with T3 in your body. 

This is very important because it's possible for your body to have a sufficient amount of total T3 but an insufficient amount of free T3 or vice versa. 

But you'd never know the difference if you only look at one marker. 

I consider free T3 to be a valuable tool in assessing the short term availability of T3 in your system. 

Total T3 represents a more stable and long-term picture of T3 in the body. 

Free T4 vs Total T3

If total T3 is so important then why do doctors order free T4 instead?

Great question.

Let's break it down so you understand what your doctor is thinking. 

Doctors know, or at least they should, that T4 is considered a pro-hormone and it's primary value comes from being a precursor hormone to T3. 

Your body makes most of the T3 by converting it directly from the stores of T4 in your body (4). 

Put another way:

T4 is only important because it helps your body produce T3. 

Doctors know this and they make the assumption that if your body has enough T4 that your body will automatically produce enough T3. 

t4 to t3 conversion in the body

This logically makes sense, but it's not what we see in the real world due to the fact that so many variables influence this conversion process (5). 

I won't get into that topic here, but you can read more about the various conditions which blunt this conversion process

Free T4 is a measurement of the amount of T4 which is free and active in your body and which can be used by your cells to be turned into T3. 

This number is important because it has potential, but not because it has activity by itself (6). 

This doesn't mean that your free T4 is unimportant, on the contrary. 

It's very important, but it's not AS important as your total T3. 

But testing your free T4, if used along with the Total T3 and reverse T3, can help you understand if your body is taking that T4 and converting it into T3 at an appropriate rate. 

Reference Ranges for Total T3 & What They Mean

Let's take a minute to talk about references ranges and where you want your numbers to be. 

First off:

The reference range you see on your own labs may be slightly different compared to the values I'm showing here and that's okay. 

Each lab creates their reference ranges based on the local population, so they may be slightly different. 

Just do your best to compare your values to those I have listed here with a focus on the "percentage" range that I recommend. 

Secondly:

These values really only apply to those people who are actively taking thyroid medication

The range of "normal" is much broader for those people who aren't on thyroid medication. 

The standard reference range for T3 ranges from 76 to 181 ng/dL. 

If you are taking thyroid medication you want your result to be in the top 30% of the reference range

By being in this area you will ensure that your body has sufficient T3 (both total and free T3) to do the work that it needs to. 

To further clarify this range, let's look at a number of examples. 

Example of a low Total T3:

total T3 reference range

The first example is one of obviously low total T3. 

This patient has a Total T3 of 75 which is flagged as low. 

In cases such as these, priority should be placed on the total T3 to try and increase it dramatically because most people with a level this low will be symptomatic (fatigue, weight gain, etc.). 

Example of a low-normal Total T3:

low normal total T3

Perhaps a more common problem that many patients will face is the idea of a low but normal total T3. 

The example I've listed above illustrates this perfectly. 

Even though the total T3 is 91 (and still within the total reference range), it's on the low side of that range. 

People who find that they have a "low but normal" total T3 will often be symptomatic much like those people with a grossly low T3 level. 

The idea here is to bring that level up with the use of thyroid medications. 

Example of an "optimal" Total T3:

optimal total t3 for weight loss

My experience has shown me that most people do well when their total T3 is right around the tippy top of the total reference range. 

You can see this result, at 171 ng/dL, is very close to that high end of the range which is 181 ng/dL. 

I find that most people feel great and optimal at levels such as this (7). 

Ideally, you'll want to adjust your medication to get you there which may take some trial and error. 

You'll also want to try and get here without suppressing your TSH to a very low level

Example of a high Total T3:

elevated Total T3 example

Lastly, we also need to talk about what constitutes a high total T3. 

The good news is, much like a low total T3, a high total T3 is easy to spot. 

When high, your total T3 is will be flagged as much and you will often experience some set of symptoms consistent with hyperthyroidism (anxiety, heart palpitations, etc.). 

You can sometimes get away with having a high free T3 due to reasons such as when your medication was taken in relation to your lab tests, but you should never have a sustained high total T3. 

*Note: all of these lab results are from patients that I have personally treated.

Putting the Picture Together

Now that you understand the importance of total T3, how are you supposed to use it to help guide your treatment?

The answer is relatively simple. 

You should focus on therapies which help preserve your total T3 and maintain a high (but not overly high) total T3 in your body. 

Because T3 is one of the best measurements of thyroid status in the body, you can use this test to help you understand how well (or not) your body is utilizing thyroid hormone. 

For instance:

Let's imagine a scenario in which you are someone who is suffering from hypothyroidism but who has a normal TSH and a normal free T4. 

From the perspective of your doctor, you are "treated" and any symptoms that you are experiencing can and should be chalked up to some other cause (this is around the time that patients get diagnosed with things like depression, or "aging").

The only problem is that unless you order the total T3 (and free T3) you can't accurately make that assumption. 

In this hypothetical instance, most of you will find that as you order your total T3 you will find that it is either grossly low or on the very low-end of the reference range. 

And, when you put this into context with other your other lab tests and your symptoms you will often find that it helps explain the full picture. 

T3 conversion booster results

If your TSH is normal and your free T4 is normal but your total T3 is low, then that is a problem that must be addressed. 

Your total T3 should take precedence over other "normal" thyroid tests because it carries more weight than they do. 

My personal recommendation is that each and every person who suspects they have thyroid problems and those who know they do have thyroid problems should get a complete thyroid lab test which includes the total T3. 

These tests may not be necessary each and every time that you check the status of your thyroid via lab tests, but they should be required for your initial evaluation. 

Conclusion

If you are someone with thyroid disease then you should have your total T3 evaluated. 

This is especially true if you are taking any type of thyroid medication including T4 only thyroid medications. 

By checking your total T3 you will have more information about how your body is processing and utilizing thyroid hormone. 

Total T3 gives you an idea as to how much free and active T3 is in your body as well as bound and inactive T3. 

My recommendation is to try and optimize your total T3 to the top 30% of the reference range while maintaining a non suppressed TSH. 

Now I want to hear from you:

Have you had your total T3 tested?

What values did you get?

How are you feeling?

Are you having trouble getting a doctor to order this test?

Leave your questions, comments or experiences below! 

References (Click to Expand)

Dr. Westin Childs

Dr. Westin Childs is a Doctor of Osteopathic Medicine. He provides well-researched actionable information about hormone-related disorders and formulates supplements to treat these disorders.He is trained in Internal Medicine, Functional Medicine, and Integrative Medicine. His focus is on managing thyroid disorders, weight loss resistance, and other sex hormone imbalances.You can read more about his own personal journey here.

22 thoughts on “How to use The Total T3 Lab Test to Help Evaluate your Thyroid”

  1. Hi Dr. Westin!
    I have been following your page for a few months now and used your advice to request testing for Hypothyroidism with a new dr that would actually listen and do a full panel. However, I don’t think they knew much about thyroid issues as they just wanted to put me on meds. I have been on Synthroid when I was pregnant with both kids but got myself off about 5 years ago. After taking on a very stressful teaching job this past Oct… I believe it onset my hypothyroidism even quicker! I am experiencing major fatigue, weight gain, brain fog, headaches, hair loss, sensitivity to cold, anxiety, mood swings…
    I really could use some direction in what supplements would be best for me to start with…and understanding my lab results a little more as I feel my new dr might not truly understand the complexity of thyroid issues.

    My results as of 3/18/19

    TSH – 5.090
    Free T3- 2.5
    Free T4 – 1.00
    Reverse T3- 16.1
    Total T3 – 97
    TgAB- 2
    TP0ab- 2

    Your videos, podcasts, and articles have been so helpful! Thank you so much for the work you do and sharing it!

    -sincerely…
    One exhausted Kindergarten teacher

  2. I had recently been on Armour (90) & had bouts of hives lasting 3 months. Through the MRT blood test, I found I was moderately reactive to pork. Have since switched to bovine NDT, Thyro-gold. I started a week ago & feel better already after my trial with a different bovine previous to this (which I heard hadn’t been giving stable results.) Thyro-gold only comes in 150 & 300’s. I started with a 150. Could you advise me on my next step? I’m wondering if I should take part of a capsule in the early afternoon or just stay with the 150 in the morning. Thank you for any help you can give.

  3. Dr. Childs,

    My recent lab results show a very low TSH (.15) and a low T3 (59). My T4 is normal. I had a thyroid obliteration four years ago and take 150 mg levothyroxine daily. My assumption from these lab results is that I am taking too much of the thyroid replacement, having crossed now into hyperthyroidism and need to reduce my dosage. I have not been able to find information on the unique combination of a low TSH and a low T3. Could you clarify this and how it is possible?
    Thank you!

    • Hi Christine,

      That’s probably not what is happening in your body because hyperthyroidism is a state of excess thyroid hormone which is typically caused by excess T3 and you don’t have that at all. So, absent of any hyperthyroid symptoms, that is probably not what is happening in your body.

      Instead, you are taking a high dose of T4 which is not being converted to T3 appropriately but which is sufficient to lower the TSH. This is most likely an indication that you are not on the right type and dose of thyroid medication.

      You can learn more here: https://www.restartmed.com/normal-thyroid-levels/

  4. Hi, I have to ask, as I’ve not seen it anywhere else. Is it possible high t3 can cause (bad) asthma symptoms? I only seem to have asthma when I can’t get my thyroid levels optimal. I had thyroid cancer, so I’ve been without a thyroid for many many years. Not one doctor is willing to entertain the fact that my on and off symptoms are thyroid related.

  5. Dear Dr. Childs,

    Thank you for the detailed, yet simple, articles on thyroid function and disorders.

    I gave birth to my son in 2017, after which I developed a goiter. I’ve had labs tests, ultrasounds and biopsies performed on my thyroid since then due to my family history of cancers.
    My thyroid markers were all normal (Total T3 – 1.09ng/ml, Free T4 – 1.3ng/mL and TSH – 0.93 u(IU)/mL) and the biopsies reported benign.

    However, I have symptoms of hypothyroidism – or so it seems: Fatigue, intolerance to cold (this has been life-long), hair loss after my pregnancy, extremely dry skin during my pregnancy that has mostly resolved, thyroid enlargement, brain fog/memory difficulty (and anxiety).

    To be fair, during the past 2 years I experienced deaths in my family including my father and I started to experience anxiety attacks and sleep disorders. Also, it has been difficult for me to distinguish what may be causing my fatigue since I have a toddler and spent many nights for years caring for my father and currently, studying for my MPH/RD. Recently, I have been exhausted and it is difficult to wake up energized.

    Bottom line – is it possible that I can have sub-clinical thyroid symptoms? Should I test for my iodine levels and would that matter? I take a morning multivitamin, liquid form.

    Thanks so much for reading and I look forward to your reply!.

    Kindly,
    Amber

  6. Hi. Just did some thyroid labs this week and here are the results:

    Tsh 1.98
    T3 107
    T4 8.0
    Free t4 1.3

    What are your thoughts?
    My appointment is next week to discuss those labs, reason my dr order this was because of symptoms.
    Sleepy, always tired, weight gain, brain fog.

    Hope I can hear from you.
    Thanks in advance.

  7. Hi, I finally got my lab results today and my Total T3 is 232, but my TSH is .015…what does this mean? I’m confused about the results. I had to call several times to have the receptionist email my results to me, but she said the doctor had not reviewed the labs yet so I’m waiting on a call. Does anyone have any idea why the results are so far out of range? Thanks.

  8. Evening, I started the Keto diet. Since then I started having severe hot flashes and cold flashes afterwards. Dry eyes, severe night sweats and heart palpitations. I started cutting back my Armour and this has helped. Do you have experience with patients having any issues such as this? Can a Keto diet help thyroid issues?

  9. I’m surprised (to say the least) to see a doctor advocating optimal T3 levels, and working with both NDT and synthetic T3, stress the importance of a non-suppressed TSH. I find that (and I know I’m not alone since I read this all the time on the thyroid forum I’m a member of) that many, if not most, patients optimally treated with NDT and/or T3, will have a TSH <0.01 and fell perfectly fine, with no symptoms of being over medicated. So I’m afraid statements like the ones you make in this (otherwise interesting) article is not going to help patients feeling well only on thyroid drugs containing T3, be that NDT, Cytomel, or any combination thereof.

    • Hi Anna,

      There’s a lot to unpack here and I won’t be able to do it in this comment but I think you are making the assumption that in order to feel well on NDT or T3 your TSH must be suppressed and this simply isn’t true. This stems from the flawed logic that free thyroid hormone levels must be optimized in order for patients to feel well or that you can brute force thyroid function with ever-increasing doses of NDT and T3. And this logic stems from the undertreatment of patients for many years with T4 only thyroid medications. But now it seems that the pendulum has swung from undertreatment to overtreatment.

      My personal experience suggests that most of the patients who fit into this category are overcompensating for other problems that are not being addressed. And using higher than normal doses of thyroid hormone to overcompensate for these issues will eventually lead to problems.

      I know from experience that having a low TSH may be necessary for some people, but your starting point (or acceptable treatment point) should not be suppressing the TSH. There may be some cases in TSH suppression where the benefits outweigh the risks, but this should be the exception and not the rule.

      There will always be consequences to suppressing pituitary hormones and those consequences should not be ignored. Many other tissues in your body have TSH receptors which will be affected by TSH suppression.

      *As a side note, just to frame this information and put it into context, I am someone who has treated hundreds of patients with all variations of thyroid hormones including T3 only, NDT only, NDT + T3, etc. etc. and in this time I have suppressed more TSH’s than I can count. The information I’m providing here is a result of these therapies and my deep dive into the literature and because of this, I would not be comfortable suppressing the TSH of my wife/mother (both who have thyroid issues).

  10. Good article, but I think you are wrong about one thing. A lot of people taking T3 medication have a very supressed TSH and that is not a problem at all. Actually one of the biggest mistakes doctors seem to make is dosing by TSH or being to careful of not surpressing TSH.
    Greetings from the Netherlands.

    • Hi Roxana,

      You are correct in that there are some people who have a suppressed TSH and who do not experience negative side effects but there is much more to it than that. For instance, pre-menopausal women have virtually no risk of bone loss with a suppressed TSH but post-menopausal women do. In addition, the length of time that your TSH is suppressed and the degree to which it is suppressed all play a role in how it affects your body.

      But to suggest that there is absolutely no risk to suppressing your TSH is just false. Whether or not you accept those risks and whether those risks outweigh the benefits of using certain thyroid medications is another question entirely.

      If you are speaking from personal experience with a suppressed TSH then you should read this article and the studies cited: https://www.restartmed.com/suppressed-tsh/

  11. Dr. Westin, my free T3 (with cytomel and NP) is at 3.1 with the high reference range being 3.9. My total T3 is at 90 with the reference range 80-175. T4 is at 0.96 and that ref. range is 0.76-1.70.

    I’m feeling horrible. I’m having many hypo symptoms. My current dose is 90 mg of NP and 25mcg of cytomel. Both taken at night. Reverse t3 hasn’t come back as of today.

    I’m fine on D, B’s, iron and I take selenium.

    Thoughts? I’m pretty much on my own on dosing, as my doc isn’t up on how to help.

  12. Dr. Childs,
    I have been doing a lot of reading on all of your research. I am very interested. My labs show TSH-0.924, Free T-4 0.68, T3 Total 77, and TPO AB-1. I am on 0.88 mcg Levoxy, and my Dr says I am at all normal ranges, yet I have multiple modules in my thyroid and gaining weight at furious rates with dieting and exercise. Hair falling out, dry skin, extreme fatigue, all the symptoms, and I continually go back and tell him about my symptoms. He specializes in Endo. His only suggestion has been switching to Synthroid as to date. Very frustrating. Any suggestions to take to him? I already have to specify which labs I want. Thank you in advance!!

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