Testosterone is a hormone produced by the human body that helps boys develop men’s features, such as muscle strength and mass, facial and body hair, and a deeper voice. It can also affect your sex drive, erections, emotional state, bone density, and sperm production.

Signs of low levels of testosterone (called low-T) include low sex drive, weaker and fewer erections than before, and wanting sex less often. Low-T also causes non-sexual signs, including an increase in body fat, lower energy, reduced muscle mass, depression, low iron (anemia), and decreased bone density.

Possible Causes

Low-T can be caused by a number of conditions, including:

  • Alcohol use
  • Chronic liver or kidney disease
  • Depression
  • High blood pressure
  • High cholesterol
  • Hormonal disorders
  • Infection
  • Injury to the testicles
  • Stress and anxiety
  • Testicular cancer (or treatment for testicular cancer)
  • Thyroid problems
  • Type 2 diabetes

Diagnosis and Treatment

We test testosterone levels with a blood test. If your testosterone level falls below about 300 nanograms per deciliter (ng/dL), we call it low-T.

We use hormone replacement therapy to treat low levels of testosterone level in your blood. In addition to erectile dysfunction, low testosterone can cause decreased sex drive (libido), fatigue, depression, decreased muscle strength, weakened bones, and difficulty with memory and concentration.

We typically administer testosterone replacement therapy using intramuscular injections, gels, patches, or long-term pellets that we insert under the skin. Oral hormone replacement therapy is not approved in the United States because it can result in liver damage. Men with prostate or breast cancer are not candidates for hormone replacement therapy because it can result in the growth of cancerous prostate or breast tissue. Potential side effects include increased cholesterol levels and red cell count and decreased sperm count.