Testosterone is the primary sex hormone in males, but it is also important in females. Most testosterone (~97%) in the blood is bound to proteins, in particular sex hormone binding globulin (SHBG) and to a lesser extent albumin. Measurements of total testosterone are often sufficient; however, they may not detect mild abnormalities of testosterone homeostasis, particularly if an individual has abnormal levels of SHBG and/or albumin. Therefore, taking accurate measurements of total testosterone, SHBG, and albumin enables the identification of any abnormalities in each of the tested biomarkers, and allows for the calculation of free testosterone, and a better understanding of the levels of the active portion of your testosterone.
Free testosterone unit of measure:
There are several different units of measurement for free testosterone: nmol/L, pmol/L, ng/dL, and pg/mL. The table below lists the conversion factors to use to change between the different units, and allow you to compare your results to other sources available.
| Unit | Conversion Factor | Unit |
| nmol/L | x 1000 | pmol/L |
| ng/dL | x 10 | pg/mL |
| nmol/L | x 28.84 | ng/dL |