Testosterone, Total


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Quest Diagnostics Test Code: 873

Testosterone circulates almost entirely bound to transport proteins. Normally less than 1-2% is free. The principal transport protein for testosterone is known as sex hormone binding globulin (SHBG) or testosterone-estradiol binding globulin (TeBG). Testosterone measurements are used to assess erectile dysfunction and to assess hormone replacement therapy.

Testosterone is one of the main sex hormones (androgens) that are found in men. Although mostly a “male” sex hormone, it is also found in small amounts in women. Testosterone is responsible for the development of secondary sexual characteristics in males, and the virilization in females. In the body, testosterone is either bound to sex hormone binding globulin (SHBG), albumin or free. A total testosterone test is mostly done in men only and it measures the free testosterone and the testosterone that is bound to SHBG and albumin.

This test is performed in following conditions such as:

• Delayed or early puberty in boys
• Erectile dysfunction in men
• Decreased sex drive in men and
• Hypothalamus or pituitary disorders
• Infertility in men and
• Testicular tumors in men


THIS TEST IS FOR MALES ONLY. Dietary supplements containing biotin (also known as vitamin B7 or B8, vitamin H, or coenzyme R) may interfere in assays and may skew results to be either falsely high or falsely low. For people receiving the recommended daily doses of biotin, draw samples at least 8 hours following the last biotin supplementation. For people on mega-doses of biotin supplements, draw samples at least 72 hours following the last biotin supplementation.


Specimen Collected
  • Blood
Estimated Time Taken

Turnaround time for the Testosterone test is typically 1-3 business days.