Free testosterone is just that, its free! It is not attached or bound to any proteins in the blood. Free testosterone is also called “bioavailable” testosterone. It is important to get this part of the levels tested because it can provide a lot more information about having low testosterone and provide an explanation as to what is going on in the body. The last thing anyone wants is to get a misdiagnosis or get prescribed a medication that is not necessary. The best way to start on the right path is to have a test done to check the free testosterone to help decide the best course of hormone replacement therapy.