The normal range for a male's testosterone level is 300 to 1,000 nanograms per deciliter, according to MedlinePlus. Higher results are sometimes caused by testicular cancer, disorders of the adrenal gland or drugs that raise testosterone levels.
There are many possible reasons for a male's level of testosterone to be less than 300. Chronic illnesses, testicular diseases and benign pituitary tumors lower results, states MedlinePlus. If the pituitary gland is producing insufficient amounts of hormones, levels are affected. Testosterone is impacted when the hypothalamus is damaged or diseased. In some cases, low levels indicate a delay in puberty.
Testosterone levels are most often checked in males when physicians suspect inadequate amounts of the hormone are being produced, MedlinePlus explains. Symptoms include late puberty, infertility, low sex drive and erectile dysfunction.