When men have low testosterone, their bodies often have trouble using sugar properly and lose muscle, which can make them more likely to develop heart disease or diabetes.

For men with low testosterone, taking testosterone therapy doesn’t seem to raise their risk of heart problems, so doctors can prescribe it without worrying too much about the heart.

For men who have both diabetes and low testosterone, taking testosterone therapy might lower their chance of having a heart attack by about 15% over about three years.

For men with low testosterone, taking testosterone therapy doesn't seem to make heart failure or heart-related death more likely—even though these men were already at high risk for heart problems.

For men with low testosterone, taking testosterone medicine might slightly raise the chance of having an irregular heartbeat, but we’re not sure if that’s actually important for their health.

In older men, having low testosterone seems to go hand-in-hand with more heart disease, but that’s probably because low testosterone often comes with other issues like being overweight, having high blood sugar, or inflammation — so it’s not necessarily testosterone itself causing the problem.