Measures the amount of inactive T3 in the body.
T3 is the primary functioning thyroid hormone that is produced in the pituitary through the conversion of T4 into T3. Free T3 represents the useable T3, what our body can make use of. The remaining inactive T3 is referred to as reverse T3 or RT3. RT3 levels may increase due to illness but is rarely associated with a thyroid condition.
Recommended with Reverse T3
Is Fasting Required? No
More Information: http://www.questdiagnostics.com/testcenter/TestDetail.action?ntc=90963