High T3 Symptoms With Thyroid Medication & Without

High T3 Symptoms With Thyroid Medication (& Without)

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T3 is the single most important thyroid hormone that your body creates. 

It is also the most powerful and biologically active of all thyroid hormones. 

But, like anything in life, too much of a good thing can be a problem. 

In this article, we are going to explore T3 in more detail. I will walk you through the symptoms which may indicate that your T3 is too high, the various causes of high T3, how to test for it, and whether or not having a high T3 is dangerous.

Symptoms Of High T3

Let’s first discuss the symptoms that tend to be associated with a high T3. 

Because T3 is the most biologically active thyroid hormone (1), it makes sense that having a high level can cause problems for the body. 

And while that turns out to be true, it’s probably not as straightforward as you may think. 

For instance:

It’s possible for you to have a high free T3 or high total T3 and experience the symptoms of excess T3. 

But it’s also possible for you to have a high free T3 or high total T3 and feel great!

In fact, many people who take thyroid medication find themselves feeling “optimal” as their free T3 rises higher and higher. 

There are some people, however, who are more sensitive to T3 and may experience the symptoms of excess T3 at “normal” levels (more on that below). 

What symptoms am I talking about? You can find a list below.

Symptoms that indicate your T3 may be too high:

  • Anxiety
  • Jittery sensation
  • Heart palpitations
  • Diarrhea
  • Headaches
  • Stomach Pain
  • Heat intolerance
  • High blood pressure
  • High blood sugar
  • Hot flashes, hot flushes, or increased sweating
  • Insomnia
  • Fatigue

It’s important that you use the combination of your symptoms AND your T3 lab tests to figure out what is happening in your body. 

If you are, however, experiencing ANY of these symptoms AND you are taking thyroid medication, then it’s possible that your T3 may be too high. 

But, we are just getting started here, so let’s dive into a little more detail…


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Testing T3 in the Serum/Blood

Now that you understand the symptoms of high T3, it’s time to talk about how to actually go about testing for it. 

If you are experiencing any of the symptoms listed above then you will want to get these tests:


  • Serum Free T3 (triiodothyronine, free) 
  • Serum Total T3 (total, triiodothyronine)


These two tests help you understand exactly how much T3 is floating around in your body, but each tells you slightly different information. 

The amount of free T3 circulating in your body is a measure of how much hormone is free and active.

Most hormones circulate in your bloodstream bound to certain proteins (2) which inactive them until a certain time and place. 

If the hormone is “free”, it means that it is not bound to a protein and it is immediately available to be used by your body. 

In endocrinology, we almost always prefer to look at free hormones (this includes free testosterone, and so on) because this measurement has more meaning than understanding the “total” amount of hormone available. 

But this doesn’t mean that the other test, total T3, is any less important!

Total T3 gives you information about the total amount of T3 available in the body (both free and bound forms). 

In this way, total T3 provides a more stable measurement of T3 in your body at any given time. 

Free T3 tends to fluctuate on a daily, hour-to-hour basis while total T3 tends to be more stable over time. 

Both tests are important, however, which is why you generally wouldn’t want to test one without also looking at the other. 

It’s possible, for instance, for your free T3 to be high while your total T3 is normal. 

In this setting, if you only looked at your free T3, without looking at your total T3, you might incorrectly think that your body is getting too much T3. 

I also recommend that you look beyond your free T3 and total T3 and into other indirect measurements of T3 status in your body with lab tests like reverse T3. 

Reverse T3 is a byproduct created when your body is not able to produce ENOUGH T3. 

High levels of reverse T3 directly compete with and block cellular activation of T3 and having high levels are associated with several disease states including obesity (3), inflammatory states (4), the use of certain medications, and chronic illness. 

Why do Some People Experience Symptoms While Others Don’t?

It’s very important to understand that the symptoms of excess T3 need to be separated from your absolute lab tests. 

What do I mean?

I mean that it’s possible for you to experience the symptoms of high T3 even with normal T3 levels. 

It’s also possible for you to not feel the symptoms of high T3 even though your labs show that your T3 is elevated. 

But, how can this be?

Well, it’s not completely understood, but I have a theory as to why this exists. 

It shouldn’t surprise you to know that each individual reacts differently to medications and hormones. 

For instance:

If I gave 100 people the same dose of thyroid medication we would find that not all 100 people would react the same way. 

Some would feel great, others would feel poorly, and still, others would experience no change at all. 

This shouldn’t surprise you. 

But why does this happen?

Part of the reason has to do with how SENSITIVE your cells are to thyroid medication compared to others. 

In order for thyroid hormone to work in your body, it must act on your cells via a nuclear receptor and make changes in your cells. 

How well your body does this depends on a number of factors including your genetics (5). 

So, there will always be some people who are MORE sensitive to the cellular effects of T3 and others who are more resistant to it. 

The more sensitive you are to T3, the more likely you are to experience the symptoms of high T3

People who are sensitive often find themselves experiencing heart palpitations or hair loss with small doses of T3. 

The more resistant you are to T3, the less likely you are to experience the symptoms of high T3

People who are more resistant to T3 find themselves needing a high free T3/total T3 to feel optimal. 

The bottom line?

Don’t be surprised if you don’t conform to the “standard reference ranges” provided by the lab company. 

You are an individual, and what your body needs is going to be unique. 

The Two Causes of High T3

There are two main ways that may find yourself with a high T3 in your body. 

It’s actually quite important to know which is causing the problem in your body because the two conditions that result in high T3 are VERY different. 

The first cause of high T3 can stem from the use of thyroid medication. 

Thyroid medication is often prescribed for those people who have an under-functioning thyroid gland or those who suffer from hypothyroidism. 

The second group of people who suffer from high T3 is those who have a problem with thyroid production in their own bodies. 

These people have a problem with the thyroid gland which results in excess production of thyroid hormone from their own thyroid gland. 

Because these conditions are so different, we need to explore them in a little more detail. 

From Thyroid Medication

You can get a high free T3/total T3 from the use of ANY thyroid medication

It is, however, most common to find yourself with a high-free T3 when using medications that contain T3 thyroid hormone. 

Medications that contain T3 include all formulations of Natural Desiccated Thyroid, T3-only thyroid medications, and sustained-release T3. 

These medications are most likely to result in a high free T3/total T3 in your body simply because they contain that hormone!

Most people, however, are not taking these medications. 

Most people use medications such as Synthroid or levothyroxine

And these medications contain only T4 (thyroxine)

It’s still possible for your body to convert that T4 into T3 (at a high rate) which may result in a high free T3/total T3, but this is unusual and not seen unless you are taking doses higher than 200mcg per day. 

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Experiencing a high T3 from thyroid medication is VERY different from a high T3 which your body produces naturally. 

When you take thyroid medication, you are effectively changing how thyroid hormone is processed and utilized in your body. 

As you take thyroid medication, your TSH will start to drop and the cross-talk between your brain and your thyroid gland declines

As this occurs, and as your TSH drops, you become reliant upon thyroid medication that you are taking by mouth to provide thyroid hormone to all of your body. 

And this is completely different from instances where your body produces excess thyroid hormone on its own (such as Graves’ or hyperthyroidism). 

This is one reason why people taking thyroid medication can have a high free T3/total T3 and NOT necessarily experience the symptoms of high T3. 

People who have conditions such as Graves’ or hyperthyroidism will always experience symptoms because the etiology of these conditions is different. 

It is important to note, however, that it is absolutely possible to take too much T3 and cause a hyperthyroid state in your own body. 

Those in this state will find it hard to miss, however, because they will experience all of the same symptoms associated with hyperthyroidism. 

Be sure that you avoid this scenario, especially if you are taking thyroid medication that contains T3 thyroid hormone. 

From Your Own Body

People who have a high T3 as a result of excess thyroid hormone production are rarely ever missed. 

If you have this condition then the chances are very high that you are experiencing all of the symptoms I listed above. 

These people present to their doctors and are often found to have high free T3 levels and a suppressed TSH. 

About 80% of people who fit this category have an autoimmune condition known as Graves’ disease (6). 

I won’t spend much time talking about these people because they are rarely ever missed and this condition must be treated because if it isn’t then you run the risk of becoming thyrotoxic or going into a thyroid storm. 

Is High T3 Dangerous?

The answer is not as straightforward as you might think. 

The short answer is it can be in some cases, but not always. 

I have found that it’s always ideal to try and mimic the normal healthy levels that your body produces naturally when it is healthy (7). 

For your thyroid, that means attempting to keep your labs in the “optimal” ranges found in this article

If you can keep your lab tests in this range then you will avoid any potential problems. 

On the other hand, I also recognize that these ranges are not one-size-fits-all. 

And for several reasons, including chronic disease states or genetics, it may be necessary for some people to go outside of those ranges. 

So, for some of you, you may find that you feel “optimal” with a free T3/total T3 which is flagged as “high”. 

If you fit into this category then you need to be cautious to prevent negative consequences. 

Having a high T3 is dangerous if it is associated with the symptoms of hyperthyroidism

Having a high T3 is probably not dangerous, as long as you are not experiencing these symptoms. 

One study (8), for instance, found that after 20 years of T3 use there was no increased risk of death, no increased risk of atrial fibrillation, and no increased risk of cardiovascular disease. 

This is very important because many doctors scare patients away from T3 by telling them that T3 will cause heart problems (atrial fibrillation) and osteoporosis (reduction in bone density). 

These side effects can be avoided if T3 is used correctly! 

But remember:

How well your body tolerates T3 depends on how you are using it!

If your dose is too small then you won’t notice any positive side effects. 

If your dose is too high then you may start to experience negative side effects. 

Pay close attention to your symptoms as you titrate or adjust your dose and follow your free T3 and total T3 lab tests. 

If you find that you are experiencing the symptoms of excess T3 then make sure to adjust your dose to avoid complications. 

It is possible to cause damage to your body with excessively high doses, but this damage will always be evident because it will be associated with symptoms

Dropping your dose should be enough to prevent this damage from occurring. 

When in doubt, don’t be afraid to go to a cardiologist to get a complete workup!

This may include tests such as an EKG and echocardiogram (9). 

In addition, be sure to monitor your bone health with DEXA scans (10). 

If you get the “okay” from your cardiologist and you find that your bone health is not osteoporotic or osteopenic, then you are in a good position. 

Final Thoughts

Monitoring your free T3/total T3 levels is important for everyone, but especially for those people who may be experiencing the symptoms of excessive T3. 

If you fall into this category, make sure you take a look at the medication you are taking and make adjustments as necessary. 

The combination of a high free T3/total T3 with symptoms is a sign that you are getting too much thyroid hormone and may be damaging your body. 

A high free t3, in the absence of symptoms, does not necessarily mean the same thing!

Now I want to hear from you:

Are you experiencing the symptoms of high T3?

What is your free T3/total T3?

Do you feel better with a higher-than-normal T3?

Are you extremely sensitive to T3 medication?

Leave your comments or questions below! 

#1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4699302/

#2. https://www.ncbi.nlm.nih.gov/books/NBK285566/

#3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3608008/

#4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3978663/

#5. https://www.jci.org/articles/view/77588

#6. https://www.ncbi.nlm.nih.gov/books/NBK448195/

#7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3752520/

#8. https://www.endocrine-abstracts.org/ea/0038/ea0038OC5.6.htm

#9. https://www.ncbi.nlm.nih.gov/books/NBK395556/

#10. https://www.ncbi.nlm.nih.gov/pubmed/11922536

signs and symptoms of too much T3 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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