I have seen a lot of statements from thyroid experts saying that free T3 and T3 levels should be on the highest end of the normal range. People have often struggled because of this, though.

What are the optimal T3 levels? How about the optimal free T3 levels? If it feels complicated to you, you’re definitely not alone. Discovered what is considered low T3 and high T3 is essential.

So, if they raise their medications or added a T3-based medication in hopes of elevating their levels into that high end, what happens? Let me tell you what you need to know today…

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The Origin of High-T3 Arguments

In a broad sense, the ultimate goal here is for people to have healthy thyroid function. In addition, realizing that lab values, and the range of lab values, may be too broad to be reflective of optimal thyroid function.

One trend that has been popular, specifically in natural medicine, is to take normal laboratory values and make a new numerical midpoint. Therefore, arguing that one should be close to that midpoint, or slightly above or below it (and that this, ultimately, reflects optimal function).

To be honest with you, lab values are all so different. They are results which need to be analyzed both individually, and collectively, to really gain a comprehensive picture about your health.

Key Insight: The truth is that lab values mean things on their own, as much as they mean things in coordination with other values.


Thyroid Scores & TSH

Your thyroid stimulating hormone (TSH) is a backward marker (Read: Should you ignore your TSH). This means that the higher your score, the more someone can be considered hypothyroid.

Key Insight: What is TSH? It is your pituitary telling your thyroid gland to work. If your thyroid is “lazy,” or not working hard enough, elevated TSH levels are essentially your pituitary scolding your thyroid to work harder.

A lot of data has shown that you can be within the normal range of TSH, but if you are on the higher end you may still experience hypothyroid symptoms in some way, or experiencing an early state of Hashimoto’s disease.

Bottom Line: The TSH should be in the range of low-normal to reflect healthy function in the body.

Free Hormones


As opposed to your TSH scores, when it comes to free hormones the levels need to be understood in reverse. This means that the more that is in your bloodstream, the more hyperthyroid you are – and vice versa.

For this reason, it would seem intuitive that if a low TSH is commensurate with good health, that a high free T3 and free T4 would be, as well. It feels like the easy answer for optimal T3 levels.

Especially T3, because of the direct effect it has on thyroid hormone (as opposed to T4, which is more of a carrier for T3).  (Read: How to test your thyroid, the definitive guide)

Bottom Line: The point here is not that T4 is bad or unnecessary, because you do need it, but that T3 on its own is quite important. In fact, I think a lot of valid stances in this discussion revolve around acknowledging the importance of T3 in the body.

High T3: The Research

I understand how it can seem totally rational to argue that T3 should be on the high side. This is essentially because it acts as a balancing act with your TSH score in its optimal range.

Is this the case, though? Let’s talk about the facts…

One big drawback is that the TSH, the T3, and the T4 all mean very different things. At the same time, they are known to change in very different ways (particularly in response to changing levels of thyroid hormone).

Your TSH is what regulates how much thyroid hormone you have in circulation. The idea here is that the thyroid itself is a “lazy” gland, and that if it is not being directly told to work it will naturally goof around and avoid working.

Consider An Example

Let’s think about it like this. If you owned a factory, with one worker, and you needed to reach a certain quota every single day.

If you came into the factory, and your worker was working at half-speed, goofing around, and taking a nap every couple of hours, you would have to tell them to get to work.

At the same time, if you told them to work too hard they might start overproducing, make a mess, and make so much product that your bottom line starts to suffer. In that case, you might even tell your worker to take a break (or take a vacation) so that your business can catch up.

Your TSH works in this exact same way. It is your body’s main lever when it comes to controlling the “work rate” of your thyroid.

This does not mean that your TSH is always going to be perfect. But it is the main control of how much hormone is being produced.

Key Insight: Your body is unable to distinguish the hormone that your body produces on its own, and the hormone you get from ingesting a pill. This means that your body only thinks in terms of its TSH score, without necessarily knowing how much hormone the thyroid itself is truly producing.

Your free T3 and T4, on the other hand, reflect what is left over in circulation. Your body basically has two main ways of controlling thyroid hormones:


  1. You govern how much your gland puts out (determined by the TSH), and
  2. Your body has ways of determining how much T3 and T4 should be in circulation

Optimal T3 Levels: The Importance of Circulation

When it comes to circulation, this would include parts of your body such as your:

If you need an easy way to think about your T3 and T4, all you need to think about is iodine.

Whether it is T1, T2, T3, T4, these are all just additional atoms of iodine attaching themselves to a thyroglobulin protein (while it might be a slight oversimplification, this is a basic concept you can use to help think it through).

The free hormones reference this circulation process that we have just described. Your body works hard to keep them where you want them, even if there are too much or too little of them coming in.

Ultimately, your body still works hard to keep your levels just right.

What Happens If You Get Too Much Thyroid Hormone?

Knowing that, it would make sense that if your body was encountering too much thyroid hormone, the first thing your body would do would be to lower the TSH.

But, you would not immediately expect your T3 levels to go up.

But, everything down below, like your T3 and T4 levels, is working harder to compensate for these added levels of hormone (essentially bailing water out of the sinking ship to keep on floating down the river).

If someone were to get too much extra hormone, from taking too much or from Graves’ disease, there is an eventual state where all of these backup mechanisms are unable to keep up.

At this point, your levels climb higher and higher, but this is not the first step in the process. In fact, it is much later in the game.

Key Insight: This is why we do not see T3 levels elevate first, even if there are good amounts of thyroid hormone.

T3 Levels: Understanding The Range

So, what can you do to keep your T3 scores in check? If your T3 levels are blatantly below range, or above, that is a distinct problem.

But, studies done on healthy people with no thyroid problems show a large distribution of T3 within the normal range.

You will often see some:

  • High
  • Moderate
  • A little higher
  • A little lower

There is even data that suggests that you would not want to be in either the highest or the lowest side of the normal range. I will come back to that and address that point a little later on in this article.

Key insight: When you are getting more hormone than you need, you do not first see the T3 come up. That is only when the body cannot regulate itself quickly enough.

What If You Were Below Range?

Why would it be, then, that you have too much hormone but you are still below range on T3. In those cases, it is about something in your peripheral control not working correctly – this could be:

Those are situations that cannot be solved by taking more thyroid into your system. All you will do is exacerbate that problem, because you will make your body work harder to regulate itself (where it is already not working hard enough).

Bottom Line: If someone has enough total thyroid hormone, based on their TSH score being in the 0.5 – 1.5 range, even if your T3 is low, you will not be able to fix that issue in a positive way by adding more T3 on top of that. It will ultimately make it to where your body becomes thyroid resistant, and you may even start seeing side effects.

NDT Therapy

Some have asked about natural desiccated thyroid (NDT) – does it have too much T3? The overall ratio found in NDT is about 4 parts of T4 to one part of T3.

The argument is then that natural circulating levels in humans is 10 parts of T4 to one part of T3. Therefore, NDT could have too much for the body.

Instead, I would ask that you consider both what is in circulation as well as what is in the body’s thyroid itself.

The body stores T3 in the body, both in the liver and gut, and can release it when the body requires more, and absorb it when there is too much.

Bottom Line: If everything is working well, and is done with a decent frequency, can make due.

A really common pitfall that I want to address, as it concerns your T3 and NDT, is the overall timing of your blood tests and your morning dose.

It is common for someone to roll out of bed, take their dose, and then test their blood. Unfortunately, this ultimately skews the results due to the increased absorption of T3 during that time.

Key Insight: In this event, a doctor may suggest that the patient in question is getting too much T3. But, everything else will look normal. In these events, if you have a blood test, be sure to take your dose of NDT afterward.

T3 Levels: The Risks

The optimal goal of medicine is to help people feel well and to help them thrive. For this reason, we always need to push against things that make us feel great in the moment. If we do not know for sure what they will do to us in the long term.

Your T3 levels are the same way. If you increase your dose, you might feel healthier in the moment, but it might not help you in the long run.

Let’s run through the different levels of T3, and what research has shown levels can mean beyond the immediate results…

Low-T3 Levels

The most important thing to know about below-normal T3 levels, there is an increased risk for cardiovascular disease.1 Essentially, you never want to be below range, as these levels typically lead to disease down the road.

High-Normal T3 Levels

On the high end of normal, we have seen some negative associations with that as well. Here is what the science has to say:

  • A risk of non-alcoholic fatty liver disease.2
  • Higher BMI and more visceral fat, higher blood pressure and fasting glucose.3
  • High values are associated with high insulin levels and HOMA-IR, and low HDL-C.4

Given these risks, we do not want to push somewhere towards a high-normal T3 level. In fact, the idea that someone should have a high T3 level just to feel good and be healthy is really quite dangerous. It can lead to long-term disease risk down the road.

One Large Study

There is one large study I want to call your attention towards. This study tracked a large group of people, and sought to find out which folks had the best response to combination thyroid therapy (meaning T3 and T4).5

In this case, the group of patients on T4-only treatment had persistent symptoms throughout. They reported remaining tired, struggling with weight, and dealing with things like muscle cramps and dry skin. They still remained symptomatic.

After checking all of their levels, the researchers put those studied on a combination of T3 and T3 treatment. A large number, about 70%, saw benefits to these symptoms. They were classified as “responders,” meaning that the symptoms they had on T4-only treatment were improved upon the introduction of combination therapy.

Here is the fascinating part. Comparing responders to nonresponders, there was really no significant difference in T3 levels – or changes down the road.

T3: Action Steps

What can you do about your T3 levels? If you are way above or below range, that is not good – you should take steps to get back within the normal range.

Key Insight: The first step is to be at optimal thyroid status, based on your TSH scores. For most ages, that can be found in the 0.5 – 1.5 range.

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What if you are within the normal range of T3, but you are not on the higher end of it? Honestly, I can tell you that it is not a problem to worry about. Healthy people are not on the highest end of the range for T3.

Furthermore, being on the highest end of the range is probably not something that correlates with good long-term health. There are risks associated with that, ones that we discussed prior in this very article.

Assess Your Thyroid Today

Interested in learning more about getting your thyroid levels just right?

First, you need to have a more comprehensive understanding of your thyroid – its current state, and what action steps you can take to heal it today.

Please, take the Thyroid Quiz today (Click Here), and learn more about what you can do to secure your long-term health.


1 – https://www.ncbi.nlm.nih.gov/pubmed/22877896
2 – https://www.ncbi.nlm.nih.gov/pubmed/28081779
3 – https://www.ncbi.nlm.nih.gov/pubmed/21670570/
4 – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4041934/
5 – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5422753/

P.S. Whenever you are ready, here is how I can help you now: 1. Schedule a Thyroid Second Opinion with me, Dr. C, Click Here for Details 2. Download and use my Favorite Recipes Cookbook Here 3. Check out my podcast Medical Myths, Legends, and Fairytales Here Dr. Alan Glen Christianson (Dr. C) is a Naturopathic Endocrinologist and the author of The NY Times bestselling Adrenal Reset Diet, The Metabolism Reset Diet and The Thyroid Reset Diet. Dr. C’s gift for figuring out what really works has helped hundreds of thousands of people reverse thyroid disease, lose weight, diabetes, and regain energy. Learn more about the surprising story that started his quest.