Reverse T3
What this test measures
Reverse T3 is an inactive form of thyroid hormone made when the body breaks T4 down by an alternative route. It rises in illness, fasting and stress. It is not part of NHS thyroid testing.
Why doctors request it
Appears on some private thyroid panels. Its clinical usefulness is limited and NHS guidance does not recommend it.
What commonly pushes it up
- Acute or long-term illness
- Fasting and very low calorie diets
- Some medicines as a class, for example amiodarone and steroids
- Taking levothyroxine
What commonly pushes it down
- Recovery from illness
Everyday reasons for a value outside the range
- Illness of almost any kind raises it, which is why it is rarely informative
- Units and ranges differ between the few labs that run it
About the sample
No fasting needed.
Upload a photo or PDF and see every line against the range your lab printed, explained in plain English. First report free.
Read my report freeThis is an educational summary of results you uploaded. It is not medical advice, a diagnosis or a treatment plan, and it does not replace the doctor who requested the test. If you are worried, or a result is marked outside range, discuss it with your doctor. Written and reviewed by a UK consultant physician. Reference ranges vary between laboratories.