For years, men have heard two conflicting messages about testosterone. One says low testosterone is bad for the heart. The other says testosterone therapy could trigger a heart attack or stroke. Both messages created confusion in my patients and, frankly, in the medical community. Today we have much clearer answers, thanks largely to one landmark study, the TRAVERSE trial. Let me walk you through what the research shows and what it means for men considering testosterone therapy.
First, low testosterone is clearly associated with poorer cardiovascular and metabolic health. A large 2024 analysis pooling data from nine studies of men found that those with the lowest testosterone levels had a higher risk of dying from any cause, and men with very low levels carried a higher risk of cardiovascular death specifically. Low testosterone is also linked with high blood pressure, thicker carotid artery walls, belly fat, insulin resistance, and chronic inflammation. Testosterone influences nitric oxide, a molecule that helps blood vessels relax. Still, low testosterone often occurs alongside aging, obesity, and poor metabolic health.
Concern about the heart safety of testosterone therapy intensified in 2010, when a trial of older men with limited mobility was stopped early because of more cardiovascular events in the testosterone group. Several observational studies later raised similar concerns, although their methods and conclusions were debated. In 2015, the FDA required manufacturers to conduct a large, rigorous safety trial. That trial became TRAVERSE, published in the New England Journal of Medicine in 2023, the largest randomized trial designed to evaluate the cardiovascular safety of testosterone therapy.
TRAVERSE enrolled 5,246 men between 45 and 80 years old. Every participant had confirmed low testosterone, with two morning readings below 300 ng/dL, along with symptoms of deficiency. Every man already had heart disease or was at high risk for it. In other words, this was exactly the group doctors worried about most. The men were randomly assigned to a daily testosterone gel or a placebo gel and followed for an average of nearly three years. Heart attacks, strokes, and cardiovascular deaths occurred at nearly identical rates in both groups: 7.0% with testosterone versus 7.3% with placebo. Testosterone gel was not associated with a higher rate of these major cardiovascular events. A follow-up analysis also found no statistically significant difference in high-grade prostate cancer, although there were too few cases to draw firm conclusions about long-term prostate cancer risk.
These results are reassuring for properly selected men with confirmed testosterone deficiency who use carefully monitored testosterone gel. However, TRAVERSE did not demonstrate that testosterone prevents heart attacks or strokes. There were small absolute increases in the risk of atrial fibrillation and blood clot in the lungs for those in the testosterone group.
One issue I watch closely in my practice is a rise in red blood cells, called erythrocytosis. Testosterone stimulates red blood cell production. Hematocrit measures the percentage of your blood made up of red blood cells. When it climbs too high, the blood becomes thicker, and this may increase the risk of cardiovascular problems and blood clots. This is why I check blood counts regularly and adjust the dose or delivery method when needed. If hematocrit becomes excessive, I may reduce the testosterone dose, change the delivery method, or in selected cases recommend blood donation or therapeutic phlebotomy, a procedure that removes blood.
Low testosterone is an important marker of cardiovascular and metabolic health, and it deserves attention. TRAVERSE provides strong evidence that, in appropriately selected men with confirmed testosterone deficiency—even those who already have heart disease or are at high risk—carefully monitored testosterone gel was not associated with a higher rate of cardiovascular death, heart attack, or stroke over approximately three years. The keys are a confirmed diagnosis, dosing that keeps testosterone within a normal range and avoid spiked levels, regular blood counts, and attention to a history of blood clots or heart rhythm problems. Just as important, hormone treatment should go alongside the foundations of heart health: reducing excess belly fat, improving how the body responds to insulin, strength training, quality sleep, and treating sleep apnea, which is commonly associated with lower testosterone levels.
