The importance of reverse T3

The importance of reverse T3 by Dr. Amie

The importance of reverse T3

Reverse T3 is a thyroid hormone that most people have never heard about but has a big impact on your metabolism.

The thyroid is a small fist size and butterfly shaped organ on the front side of our neck.1 Even though it is comparatively small it has a huge impact on our bodies. It regulates our metabolic rate by controlling our heart, muscle, digestive, and brain function. 2

The way it does that is by producing hormones that function as little messengers delivering information from one organ to another. The two main hormones that thyroid glands produce are triiodothyronine (T3) and thyroxine (T4).

T4 is the inactive form and is the most abundantly produced (80%). It is released into the blood stream and is converted to T3, the active hormone, when it arrives at the target organ. What most people don’t know is that T4 is also able to convert to reverse T3, a hormone that looks a lot like the active T3 but is metabolically inactive. You could say that reverse T3 is the imposter trying to mimic the active T3 but having the opposite effect.3

What does reverse T3 do?

 As said before, reverse T3 looks a lot like T3 and is even able to dock on the free T3 receptors on cells. Just like a key, it can enter a lock without being the correct key. In this way it competes with T3 for those receptors.  The higher the amount of reverse T3, the higher the chances are that the wrong keys are blocking the receptor locks and free T3 is not able to enter the cell.

At first thought this sounds like a bad thing, but our body rarely does anything without having a reason for it. There are situations in which it is beneficial for the body to have less thyroid function increasing the metabolic rate. An example for this situation is when your body is in survival mode, for example due to trauma, infection, or injury. Your body in those moments wants to store energy to be able to use it for healing.

What is the optimal level for reverse T3?

If you are not in an acute response due to the situation mentioned above, optimal levels for reverse T3 is below 15 ng/dl. Depending on the other thyroid hormones and clinical judgement it may even be beneficial to have optimal values below 11-12 ng/dl.

Are there any other reasons why my reverse T3 is elevated?

 While there are physiological and other important reasons for reverse T3 to be elevated, our modern way of living often leads to elevated levels due to pathologically prolonged stress periods. Reasons for elevated T3 are physical and emotional stress, toxin exposure, insulin resistance, poor quality supplement use, excessive exercise, inflammation, low calorie dieting, chronic untreated gut infections, as well as some medications.

What can I do to lower reverse T3?

Give your body everything it needs to convert correctly from T4 to T3. Your body needs sufficient iron, ferritin levels, magnesium, and iodine to be able to function properly as well as other hormones such as sex-hormones, insulin and cortisol needed to be balanced. Another way to reduce T3 is by practicing stress reducing activities like meditation, yoga, or breathing techniques.

In summary

Reverse T3 acts like an imposter to free T3, the active thyroid hormone. It stops T3 from entering the cells and from acting as a metabolic rate enhancer. In moments of extreme stress like trauma, or infection it helps your body to store energy to survive. Daily it is essential to have optimal reverse T3 levels.


  1. The Butterfly (Gland) Effect. The Portland Clinic. Published January 25, 2018. Accessed July 22, 2021.
  2. Information NC for B, Pike USNL of M 8600 R, MD B, Usa 20894. How Does the Thyroid Gland Work? Institute for Quality and Efficiency in Health Care (IQWiG); 2018. Accessed July 22, 2021.
  3. RT3 – Clinical: T3 (Triiodothyronine), Reverse, Serum. Accessed July 22, 2021.
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