It is believed that over 13 million men in the U.S. have low testosterone. This deficiency is linked to the body's inability to produce enough testosterone, the most important sex hormone in males.

Testosterone replacement therapy can have side effects. Only men with symptoms of low testosterone and blood levels that confirm this as the cause of symptoms should consider testosterone replacement. Talking with your doctor is the only way to know if testosterone therapy is right for you.

Subtle Symptoms of Low Testosterone

The symptoms of low testosterone are sometimes obvious, but they also can be subtle. Testosterone levels decline naturally in men as they age over decades. But certain conditions can also lead to an abnormally low level. Symptoms of low testosterone include:

• Low sex drive (libido)
• Erectile dysfunction
• Fatigue and poor energy level
• Decreased muscle mass
• Body and facial hair loss
• Difficulty concentrating
• Depression
• Irritability
• Low sense of well-being

If a man has symptoms of low testosterone and tests show he has an abnormally low testosterone level (less than 300 ng/dl), a doctor may suggest treatment. For millions of men who have low testosterone levels but no symptoms, no treatment is currently recommended. It is has also not been approved for treating men with low levels because of aging.

Forms of Testosterone Supplements

Testosterone replacement therapy is available in several forms. All can improve testosterone levels:

Skin patch (transdermal): Androderm is a skin patch worn on the arm or upper body. It's applied once a day.

Gels: AndroGel and Testim come in packets of clear testosterone gel. Testosterone is absorbed directly through the skin when you apply the gel once a day. AndroGel, Axiron, and Fortesta also come in a pump that delivers the amount of testosterone prescribed by your doctor. Natesto is a gel applied inside the nose.

Mouth patch: Striant is a tablet that sticks to the upper gums above the incisor, the tooth just to the right or left of the two front teeth. Applied twice a day, it continuously releases testosterone into the blood through the oral tissues.

Injections and implants: Testosterone can also be injected directly into the muscles, or implanted as pellets in the soft tissues. Your body slowly absorbs the testosterone into the bloodstream.