What does the Reverse T3 (rT3) - rT3 blood test mean? Get a free analysis of your blood test now. Here's what you get with our free analysis:
The Reverse T3 (rT3) test measures the levels of an inactive form of thyroid hormone in the blood. rT3 is produced from T4 but does not have the same metabolic effects as T3. This test is often used to evaluate thyroid function in conjunction with other thyroid tests, particularly in cases where standard thyroid tests yield conflicting or unclear results. Elevated rT3 levels can indicate a condition called 'euthyroid sick syndrome' or 'non-thyroidal illness syndrome,' which can occur in severe illnesses, starvation, or chronic stress. The rT3 test can help distinguish between true hypothyroidism and other conditions that might affect thyroid hormone metabolism.
A low rT3 level is generally not considered clinically significant on its own. It may indicate:
However, low rT3 should always be interpreted in the context of other thyroid function tests and clinical symptoms. It’s rarely used as a standalone diagnostic tool.
Elevated rT3 levels can indicate:
High rT3 should be interpreted alongside other thyroid tests and clinical presentation for accurate diagnosis and treatment planning.