Hormone & Endocrine - Bloody Good
Thyroid

Reverse T3 (rT3)

The Reverse T3 (rT3) Test measures a form of thyroid hormone that is inactive. High rT3 levels may happen during stress, illness, or inflammation when the body slows metabolism. This test may help give a broader picture of thyroid and metabolic function alongside a Thyroid Function Tests (TSH, T3, and T4).

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Reverse T3 (rT3)

Experiencing thyroid symptoms despite normal tests, chronic stress, or unexplained fatigue and want assessment of thyroid hormone conversion for optimal function?

Overview

Think of your thyroid as having both a gas pedal and a brake pedal for your metabolism. The Reverse T3 test measures your body's "brake pedal" hormone – the inactive form of thyroid hormone that can actually block your active thyroid hormones from doing their job. When you're under chronic stress, fighting illness, or dealing with other health challenges, your body sometimes converts your thyroid hormone into this inactive form as a protective mechanism, like pumping the brakes on your metabolism.

This test is particularly helpful if you're experiencing classic low thyroid symptoms – like fatigue, weight gain, brain fog, or feeling cold – but your standard thyroid tests keep coming back "normal." Elevated reverse T3 can explain why you might feel hypothyroid despite having what appears to be adequate thyroid hormone levels, since this inactive hormone essentially competes with your active hormones for space in your cells. By identifying this hidden thyroid roadblock, you and your healthcare provider can better understand what's really happening with your metabolism and explore more targeted treatment approaches to help you feel like yourself again.

Reviewed by Dr. Vu Tran
Bloody Good’s Chief Medical Officer

Symptoms

You may benefit from this test if you experience:
Feeling tired all the time Extreme fatigue that doesn't improve with rest Always feeling cold even in warm weather Difficulty losing weight despite diet and exercise Feeling sad or down most of the time

Purpose

Essential for individuals with persistent thyroid symptoms, normal standard thyroid tests, chronic stress, or anyone needing comprehensive thyroid conversion assessment.

How to prepare

Fast for 8-12 hours before testing. Take sample before 10am. Drink only water during fasting period. Avoid training 24-48 hours prior to test.

Understanding results

Results show reverse T3 levels and T3/rT3 ratio. Elevated reverse T3 or low T3/rT3 ratio may indicate thyroid conversion problems requiring specialized treatment.

After the test

Address elevated reverse T3 through stress management, nutritional support, treatment of underlying conditions, and specialized thyroid hormone therapy. Work with thyroid specialists for complex cases.

Frequently Asked Questions

  • Reverse T3 is an inactive form of thyroid hormone that can block active T3, potentially causing hypothyroid symptoms despite normal standard tests.
  • Causes include chronic stress, illness, caloric restriction, certain medications, liver dysfunction, and conditions affecting thyroid hormone conversion.
  • Symptoms may include fatigue, weight gain, brain fog, depression, cold intolerance, and other hypothyroid symptoms despite normal TSH/T4.
  • Treatment focuses on addressing underlying causes, stress management, nutritional support, and sometimes specialized thyroid hormone therapy.
  • Testing is useful when hypothyroid symptoms persist despite normal standard thyroid tests or in complex thyroid presentations.
  • Yes, through stress reduction, treating underlying conditions, nutritional support, and addressing factors that promote reverse T3 production.
Reverse T3 (rT3)

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What to expect

We want you to feel bloody good—inside and out. Regular testing isn’t just about checking your current health; it helps you spot abnormal values you might not know about.

1

Book your referral

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2

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3
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View your lab results and receive a personalised review from the secure Bloody Good platform.

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