If you're a man of a certain age, you've probably noticed all the ads for supplemental testosterone, hinting that taking the male hormone could cure all that ails you, from waning sexual performance to dwindling muscle mass and strength.

And the ads seem to be working: The number of prescriptions written for testosterone have skyrocketed by more than 300 percent since 2001, reaching 7.2 million in 2013, according to an April 2016 analysis by researchers at Massachusetts General Hospital, Weill Cornell Medical College, New York University, and Stamford University School of Medicine. And an estimated 70 percent of those prescriptions for testosterone boosters are written for men between the ages of 40 and 60.

Other research suggests that all those prescriptions are good for the drug companies that make and sell the pills: testosterone sales topped $1.6 billion in 2011, according to a 2013 study in JAMA.

But is extra testosterone good for you, too?

The Testosterone Problem

Although some men who take testosterone report better sexual function, most don’t. That's in part because erectile dysfunction usually stems from low blood flow to the penis, caused by high cholesterol levels or high blood pressure, not low testosterone, according to the American Urological Society.

And taking a testosterone booster doesn’t improve physical stamina or energy, either, according to a study funded by the National Institutes of Health and published in February 2016 in the New England Journal of Medicine.

“My patients come in all the time asking for it after seeing all the direct-to-consumer ads telling them they absolutely need to take it,” say Adam Cifu, M.D., a professor of medicine at the University of Chicago and co-author of “Ending Medical Reversal."

“Since there is so much demand, physicians feel pressure to prescribe it not to lose patients.” Some doctors may believe what Cifu calls “marketing hype­—that testosterone will make a 60-year-old man with slightly low testosterone feel better. But it’s medicalizing natural aging.”

Real Risks

Most older men won’t feel better or see health benefits from taking a testosterone booster. In fact, older men who are prescribed it appear to have a higher risk of dying from any disease as well as from a heart attack or stroke, according to a 2013 JAMA study.

Another study found that men over age 65 on testosterone therapy might have twice the risk of having a heart attack or stroke.

Other research suggests that testosterone boosters might fuel the growth of prostate cancer, and reduce sperm counts, too. Established risks include blood clots in the legs, sleep apnea, an enlarged prostate, enlarged or painful breasts, and swollen feet or ankles.

In addition, the gel forms of testosterone, applied under your arm or on your upper arm and shoulder, can be transferred to others if you don’t wash the area after applying it. Children exposed to the hormone have experienced enlargement of the penis or clitoris, growth of pubic hair, increased libido, and aggressive behavior. Women can experience acne and the growth of body hair and, if they are pregnant or breast-feeding, can transfer the hormone to their babies.

What to Do Instead

If you're feeling as though you have low energy or are having sexual problems, don't assume that low testosterone is the cause, or that a testosterone booster is the solution. 

Stress, lack of sleep or exercise, and feelings about your partner can also sap your vim and vigor. Plus, diabetes, obesity, and pituitary tumors can contribute to low testosterone, as can some drugs. So they should be ruled out first.

"There’s nothing romantic or age-defying about a drug that comes with long-term risks to you and the people you live with," says Marvin M. Lipman, M.D., Consumer Reports' chief medical adviser.

Instead, try safer ways to bring back that lovin’ feeling: Eat right, exercise, reduce stress, and have a long talk with your partner and your doctor. If you do start treatment, reassess after a few months and watch for worrisome side effects in you and those around you.