Reverse T3 (rT3)

TIMING: Follow standard thyroid draw timing — take meds as usual the day before, draw first thing AM before that day's dose. Elevated rT3 (above 15–20 ng/dL) is considered significant by the functional medicine community as evidence of poor T4→T3 conversion, often driven by chronic stress, high cortisol, inflammation, or low iron. Standard medicine largely disregards rT3. STTM recommends calculating the Free T3:Reverse T3 ratio — above 20 (using pg/mL:ng/dL) is generally adequate conversion. Below 20 suggests the body is converting T4 to inactive rT3 instead of active T3. These notes reflect common practices in thyroid/functional medicine communities.

Reflects common practices in thyroid, BHRT, and functional medicine communities. This may differ from standard clinical guidelines. Not medical advice — always discuss with your provider.