FT3 (25T/Kit) refers to a testing kit used to measure levels of free triiodothyronine (FT3) in the blood. FT3 is the unbound, biologically active form of triiodothyronine (T3), which is a thyroid hormone involved in regulating metabolism, growth, and development in the body.

The kit, labeled as “25T/Kit,” indicates that it contains 25 tests, meaning it can be used to measure FT3 levels in 25 blood samples.