Q: I'm a generally healthy 72-year-old man, but my energy level and sex drive are not what they were 10 years ago. How do I know if I need to take testosterone?

A: Based on the ads you see on TV, you'd think the answer is straightforward. But experts are still trying to understand which men benefit from testosterone therapy.

If there were no side effects, a trial of testosterone would usually be reasonable. But there are potential problems and some of them can be serious.

Doctors won't hesitate to treat men with a low blood testosterone level and classic symptoms of low testosterone. Those symptoms include low sex drive, low sperm count, loss of body hair and hot flashes. Low bone density with a low blood level is also a good reason to take testosterone.

But few men fit the classic picture. Most men wondering about testosterone have non-specific symptoms. Less interest in sex is the most common one.

Other symptoms you might be experiencing include:

Difficulty concentrating

Feeling down

Trouble sleeping

Lower energy level

Less "get up and go"

Decreased muscle mass

These non-specific symptoms may or may not be related to low testosterone. Some men with at least one of these symptoms have low testosterone levels. But many others with one or more of these symptoms have normal levels.

Even if your testosterone level is low, it's possible that these symptoms might be due to depression, low thyroid function or some other medical problem. And that should be considered first.

Testosterone therapy carries risks. The U.S. Food and Drug Administration just issued a new warning about an increased risk of blood clots in veins related to testosterone therapy. This is in addition to prior concerns about a higher risk of heart attack and stroke.

Talk with your doctor about the potential benefits vs. the risks. If the balance tips in favor of you moving forward, then trying testosterone might be a reasonable thing to do.

(Howard LeWine, M.D., is a practicing internist at Brigham and Women's Hospital, Boston, Mass., and Chief Medical Editor of Internet Publishing at Harvard Health Publications, Harvard Medical School.)

(For additional consumer health information, please visit http://www.health.harvard.edu.)

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