This blood test measures both total testosterone and free (calculated) testosterone. Total testosterone reflects all testosterone in the blood, including hormone bound to proteins such as sex hormone-binding globulin (SHBG) and albumin, as well as the small unbound portion. Free testosterone represents the fraction not bound to proteins. In this version, free testosterone is calculated using measured total testosterone, SHBG, and albumin values rather than measured directly. The test is used to evaluate testosterone levels in the body. It may be ordered to help assess symptoms that can be associated with low or high testosterone, to investigate fertility concerns, or to monitor hormone-related conditions. Because a large portion of testosterone is protein-bound, measuring the free fraction can provide additional information beyond total testosterone alone. Interpretation of results should be done by a healthcare provider.