What Are the Side Effects of Low Testosterone in Men?

Symptoms of low testosterone levels in men include depression, fatigue, weakness and the loss of sex drive, according to WebMD. Testosterone levels usually begin to decline after age 30. Low testosterone levels cause the bones to lose density, increasing the chances of fractures. Normal testosterone ranges are between 300 and 800 nanograms per deciliter, but symptoms may not be evident until levels drop to the 100 to 200 nanograms per deciliter range.