The Testosterone, Free (Direct), Serum with Total Test will determine the level of testosterone (free and total) in your blood. Testosterone is a hormone (commonly produced in males, but is also in females in small amounts) that affects sexual features and development. Testosterone levels explode in men after puberty and continue to rise until about age 40. Overall, this test will give you a better understanding of how much testosterone is in your blood. If you’re taking steroids, a testosterone supplement, or any other anti-aging medicine, you should consider Testosterone, Free (Direct), Serum with Total Test. These supplements promote muscle and bone growth, but too much can affect your body in other ways.