Testosterone, Free (Direct)

The free testosterone blood test measures the amount of testosterone in the blood that is not bound to proteins such as albumin, Sex Steroid Binding Globulin (SSBG) or Sex Hormone Binding Globulin (SHBG).  The free testosterone blood test combined with the total testosterone blood test provide an excellent level of detail regarding your levels of this critical hormone.

The term bio-available testosterone (BAT) refers to the sum of free testosterone plus testosterone bound to albumin, as the binding with albumin is easily broken.  Some clinicians suggest that BAT represents the active amount of testosterone that readily enters cells and is a more illuminating measurement than total testosterone.