Higher levels of testosterone can have significant health benefits for some men, such as being less vulnerable to high blood pressure, heart attacks, frequent colds and obesity. These men are also more likely to rate their health as "good to excellent" rather than "fair to poor". (Studies show self ratings of health correlate highly with physicians' assessments.) On the downside, some - but not all - men with higher levels of testosterone are more likely to engage in behavior that cancels out the beneficial effects of testosterone. Those with higher levels of testosterone are more inclined to smoke, drink alcohol excessively and indulge in risky behavior that leads to injury. The biggest detriment to health by far is the tendency for high testosterone men to smoke.

In a study published 1997, researchers studied testosterone and health in a sample of 4,393 men between the ages of 32 and 44 who had served in the military between 1965 and 1971. The men were interviewed and medically examined. Testosterone was measured in plasma from blood drawn at 8am. Concentrations ranged from 53 to 1,500 ng/dl with an average of 679. Comparison of men with slightly below average levels of testosterone (400ng/dl) with men with slightly above average levels (800ng/dl) revealed significant differences in health indicators.

Men at the higher level were 45% less likely to have high blood pressure, 72% less likely to have experienced a heart attack, 8% less likely to have 3 or more colds in a year, and 45% less likely to rate their health as fair or poor.

On the other hand, men at higher levels were 25% more likely to report one or more injuries, 32% more likely to imbibe 5 or more drinks in a single day and 151% more likely to smoke.

It is not yet fully understood how testosterone benefits health or leads to behavior detrimental to health. It is clear, however, that men with higher testosterone levels are at higher risk for negative health outcomes. But there are many men with higher testosterone who don't engage in health risk behavior and who do realize testosterone-related health benefits.