Why Hypothyroid Patients Should Never Ignore High Reverse T3 Levels

High Reverse T3 Levels

Reverse T3 is a valuable thyroid marker that most doctors unfortunately never test their patients for. However, just because conventional medicine doesn’t recognize its importance, it doesn’t mean that elevated reverse T3 cannot cause or contribute to your hypothyroid symptoms and should be ignored.

In fact, since reverse T3 (rT3) is seldom evaluated and taken into account when choosing thyroid treatment, you may be at risk to never get a chance to recover from hypothyroidism and find out the true cause why you continue to suffer from hypothyroid symptoms despite all test results in the normal range.

In conventional medicine reverse T3 is seen as an inactive degradation product with no metabolic effects on the body. The important physiological role of reverse T3 has only recently emerged and shows that reverse T3 can indeed provide a lot of value.

TSH and T4 thyroid tests alone don’t provide us with information whether active T3 hormone reaches your cells and tissues and how effective it performs its metabolic action. It is the reverse T3 that is one of the important indicators that allows to evaluate how hypothyroid you are on a cellular level.

There are research studies that:

”…demonstrate that TSH and/or T4 levels are poor indicators of tissue thyroid levels and thus, in a large percentage of patients, cannot be used to determine whether a person has normal thyroid levels at the tissue level. Reverse T3 inversely correlates with physical performance scores and the T3/rT3 ratio is currently the best indicator of tissue levels of thyroid.”

What Is Reverse T3?

Elevated Reverse T3

Reverse T3 is a thyroid hormone that is produced in your body through a conversion from T4. The majority of circulatory reverse T3 is synthesized by deiodination of one iodine atom of thyroxine (T4) in your peripheral tissues such as liver, kidney and muscles.

The major role of reverse T3 is to block the action of active T3. This may sound counter intuitive but this is a part of your body’s self-defense mechanism to protect you from too much active T3, for example in hyperthyroidism, Hashitoxicosis and thyroid storm.

Reverse T3 is used by your body in case it has to “put on emergency brakes” and lower the amount of T3 when more T4 converts to T3 than it can handle. This is a natural adaptive mechanism that reduces energy expenditure and protects you from a high metabolism.

Your reverse T3 levels are directly connected to how much T4 you have and are usually low in hypothyroidism and high in hyperthyroidism. Problems arise when excessive reverse T3 is produced along with less T3 and it is blocking the conversion of T4 to T3 in people with hypothyroidism and Hashimoto’s disease making them even more hypothyroid.

Causes Of High Reverse T3

Any one of the following conditions can create a situation when the conversion of T4 to reverse T3 is being favored over the production of T3:

  • Leptin resistance
  • Inflammation
  • Dieting
  • Nutrient deficiencies such as low iron, selenium, zinc, chromium, vitamin B6 and B12, vitamin D and iodine;
  • low testosterone;
  • low human growth hormone;
  • Insulin dependent diabetes;
  • pain;
  • stress;
  • environmental toxins;
  • free radical load;
  • haemorrhagic shock;
  • liver disease;
  • kidney disease;
  • severe or systemic illness;
  • severe injury
  • surgery;
  • toxic metal exposure.

In either condition a person deals with prolonged periods of stress when adrenals produce more cortisol to deal with stressors. High cortisol inhibits the 5-deiodinase enzyme type 1 and conversion of T4 into T3 leading to an increase in reverse T3. As a result, a person has low T3, too much reverse T3 or an improper T3/rT3 ratio.

Both T3 and reverse T3 bind to thyroid hormone receptors. However, while T3 stimulates healthy metabolic activity of the receptors supporting your metabolism, reverse T3 does the opposite and blocks receptor sites from T3 activation which may cause hypothyroid symptoms.

For most hypothyroid and Hashimoto’s patients having too much reverse T3 means that regardless of whether or not their TSH is in the normal reference range, they remain hypothyroid on the cellular level. This condition is called cellular hypothyroidism and is often the reason why a person has persistent hypothyroid symptoms that just don’t go away with a standard hypothyroidism treatment.

How To Test For Reverse T3

Reverse T3 test

Checking reverse T3 is not a part of routine evaluation for thyroid disease. However, reverse T3 can be measured by a simple blood test which is fairly inexpensive.

An indication for the reverse T3 test can be a combination of factors including hypothyroid symptoms and other thyroid tests such as normal TSH with normal or high T4 and low T3. In addition, a sex hormone binding globulin (SHBG) test can help to evaluate the cellular levels of T3.

Calculation of T3 to reverse T3 ratio can give an idea about

The ankle reflex relaxation time (ART), which can be measured using an achillometer or kinemometer, also correlates well with the severity of cellular hypothyroidism. But unfortunately, this simple thyroid testing tool is underutilized in clinical practice.

How To Lower Reverse T3 And Improve T3/rT3 Ratio

High Reverse T3 thyroid Hormone

Successful reverse T3 treatment usually involves:

First, balancing your cortisol levels and calming down the stress response.

If a person is under chronic stress and cortisol is high, it is very important to address it before starting work on lowering reverse T3 levels. When cortisol remains elevated it continues to inhibit the 5-deiodinase enzyme 1 and as a result the production of rT3 remains high reducing the effectiveness of thyroid treatment.

On the other hand, low cortisol levels also need to be treated because:

  • Low cortisol reduces the number of available T3 receptors and prevents T3 from entering the cells. This hinders the recovery while on thyroid treatment.
  • People with low and sub-optimal cortisol levels respond poorly to thyroid medication in general.
  • Hypoglycemia or low blood sugar is a very common imbalance that comes together with low cortisol issues and is also known to increase reverse T3.

Second, correcting any other identifiable factors that inhibit the 5-deiodinase type 1 activity and lead to high reverse T3

such as:

  • Nutritional deficiencies of selenium, zinc, vitamins B6, B12 and E, iron and iodine
  • Low sex hormones

Third, only after all these aspects above are addressed a proper thyroid therapy needs to be initiated.

The use of thyroid drugs should have a goal to reduce excess of T4 and gradually increase T3 levels until reverse T3 gets in the middle and Free T3 is in the upper part of their normal reference range.

When you have high reverse T3 and hypothyroid symptoms being on T4-only drugs or increasing their dose can make you feel even worse. Adding T4 into your system is like giving a fire more fuel to burn and more T4 is going to convert into more reverse T3.

When it comes to cellular hypothyroidism it is important to look beyond the standard T4-only treatment. Patients feel better on a combination T4 and T3 thyroid therapy and especially when taking slow-release T3. If a person gets T3 instead of T4, the body will have less T4 to convert to reverse T3 reducing its levels naturally and hypothyroid symptoms will slowly subside.

The T3/rT3 ratio can be used to determine whether thyroid medication should be considered to correct high reverse T3 levels. Ideally the ratio of T3/rT3 multiplied by 100 should be in the upper end of the normal reference range of 1.06 to 2.2. If this ratio is at the low end of this range or below then rT3 is still high and a slow-release T3 thyroid should be used to achieve the best results.

It is important to remember, that thyroid medication alone is not always the right answer when it comes to the high reverse T3 problem. Your first step should be trying to eliminate possible contributing factors to high reverse T3 before reaching for a T3 medication, otherwise your treatment can be ineffective.

The best place to start is this hypothyroidism program because it covers all cortisol imbalances and nutritional deficiencies involved in solving problems associated with high reverse T3.

Thyroid Hormone Pathways

P.S. There is a lot more to discover about hypothyroidism and Hashimoto’s disease. Get FREE e-mail course Nutritional guide for hypothyroidism and Hashimoto’s disease to learn more.


1.Clinical challenges in thyroid disease: Time for a new approach? Maturitas. 2016 May;87:72-8.

2. Thyroid Hormone Concentrations, Disease, Physical Function and Mortality in Elderly. Men. J ClinEndocrinolMetab 2005;90(12):6403-9

3. Thyrotoxicosis with low T3 and high reverse T3 levels. 9 cases. Nouv Presse Med. 1980 Jan 5;9(1):30.

4. Does Reverse Triiodothyronine Testing Have Clinical Utility? An Analysis of Practice Variation Based on Order Data from a National Reference Laboratory. Thyroid. 2018 Jul;28(7):842-848. doi: 10.1089/thy.2017.0645. Epub 2018 Jun 13.

About Marina Gutner, PhD

Marina Gutner, PhD, researcher, medical writer, thyroid blogger, founder and Admin of Outsmart Disease who writes about life-changing treatments for hypothyroidism, Hashimoto's thyroiditis and autoimmune disease and how to balance hormones in women