Testosterone testing is used to diagnose several conditions in both men and women, as well as detecting low levels or deficiencies in men. Testosterone is the main sex hormone in men and is responsible for male physical characteristics. Typically testosterone is considered to be a male sex hormone, but it is present in the blood of females as well.
This testosterone blood test measures the total amount of testosterone that is bound to proteins in the blood as well as testosterone that is not bound (free testosterone). Approximately two-thirds of testosterone circulates in the blood bound to SHBG and less than one-third is bound to albumin. A small percent (less than 4 percent) circulates in the blood as free testosterone.