Men over 45 who take testosterone to boost low levels may be 78% more likely to have a prostate problem detected than those who don’t, so doctors should keep a close eye on them during treatment.

For men over 45 taking testosterone therapy, their blood often gets thicker with more red cells, making it almost four times more likely to reach unsafe levels—so doctors need to check their blood regularly.

For men between 55 and 67, taking testosterone therapy doesn’t seem to increase their chances of getting prostate cancer compared to men who don’t take it, based on a long-term study of nearly 3,000 men.

For men over 45, taking testosterone supplements doesn't seem to make heart problems, sleep apnea, or dying any more likely than not taking them.

For men over 40 with low testosterone, taking testosterone supplements might slightly improve how they feel in certain areas of daily life—like energy or mood—compared to taking a sugar pill.

For men between 55 and 67, taking testosterone therapy doesn’t seem to make them more likely to die from any cause over 18 years — their risk is about the same as men who don’t take it.