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How Is Low Testosterone Diagnosed?
Many symptoms of low testosterone
can occur in other diseases, so low testosterone
usually cannot be diagnosed based on signs and symptoms alone. This is especially true in adult men, for whom the symptoms can be quite subtle and nonspecific.
Therefore, a healthcare provider should obtain a detailed medical history and perform a thorough physical examination. If low testosterone is suspected, he or she will then use certain tests to confirm a diagnosis and find its cause.
Different Testosterone Tests
As you would probably suspect, the first test used to diagnose low testosterone is usually a blood test. Specifically, a "serum total testosterone" test is typically used. This is the basic, "run-of-the-mill" test that can be handled by most laboratories.
In rare situations, your healthcare provider might want to use a "serum-free testosterone" test. It is "free" because it measures only the testosterone that is not bound to proteins in the blood. Only a few laboratories in the country are capable of performing this test properly. The "serum total testosterone" test that is almost always used measures both the bound and unbound testosterone.
Although each lab may vary slightly in the values they consider to be normal, based on the specific testing equipment and chemicals used, the standard normal range for serum total testosterone is usually 300 to 800 ng/mL. Anything below 300 ng/mL is usually considered a low testosterone level
Keep in mind that testosterone levels vary from day to day, and from hour to hour during the day. Therefore, it is usually recommended to always have your test drawn in the morning (8:00 a.m. is ideal). If you are already taking testosterone, the timing of your blood test will depend on the type of replacement medication you are taking. Sometimes, a second test will be recommended to verify the initial results, especially if the results are borderline.