An SHBG blood test measures the level of a protein called sex hormone binding globulin (SHBG) in a sample of your blood. SHBG is made mostly in your liver. It binds (attaches) to sex hormones such as testosterone and estrogen and helps control how much of these hormones are active in your body.

Measuring SHBG levels can provide information about how much of your testosterone is active in the tissues of your body.

Source: MedlinePlus, U.S. National Library of Medicine