Does TRT Raise Heart Attack Risk? What the New Research Actually Shows

The fear around testosterone replacement therapy and heart attacks did not come from nowhere. It came from a wave of observational studies published in the early 2010s that suggested men on TRT had higher rates of cardiovascular events, and those studies got picked up by news outlets and regulatory agencies and shaped how an entire generation of doctors talked to their patients about testosterone. The problem is that observational studies cannot prove cause and effect, because the men who were prescribed TRT were already sicker, older, and higher risk than the general population, so you were essentially comparing sick men who got testosterone to healthier men who did not, and then concluding that testosterone caused the sickness.

That is the flaw at the center of the old fear. Not the question itself, which is a legitimate one, but the way the evidence was collected.

To actually answer whether testosterone causes cardiovascular harm, you need to take a large group of men, split them randomly into two groups, give one group testosterone and the other a placebo, and follow them long enough for events to show up. You need both groups to be similar at the start so the only variable is the treatment. That is what a randomized controlled trial does, and for years there was not one large enough to give a definitive answer on TRT and heart disease specifically.

That changed in 2023 with the TRAVERSE trial, published in the New England Journal of Medicine. Researchers enrolled 5,246 men between the ages of 45 and 80 who had low testosterone, defined as less than 300 nanograms per deciliter on two separate measurements, and who also had either existing cardiovascular disease or a high risk of developing it. These were not healthy young men. These were men with the exact profile you would worry about most if testosterone were dangerous for the heart.

They were randomized to receive either a daily testosterone gel or a placebo gel and followed for a median of 33 months, which is close to three years.

The primary outcome the researchers were tracking was something called MACE, which stands for major adverse cardiovascular events, meaning heart attack, stroke, or cardiovascular death. In the testosterone group, 7.0 percent of men experienced a MACE event. In the placebo group, it was 7.3 percent. The difference was not statistically significant, and the trial met its prespecified criteria for non-inferiority, meaning testosterone was officially shown to be no worse than placebo for these outcomes.

The men on testosterone were not better protected from heart attacks. But they were not at greater risk either, and that matters enormously given what was believed before.

A meta-analysis published in the Journal of the American College of Cardiology pooled TRAVERSE together with every other randomized controlled trial that had been done on testosterone and cardiovascular outcomes, and the conclusion held across the combined data. No increased risk of heart attack, stroke, or cardiovascular death. An expert review published in Andrology in 2026 reviewed both TRAVERSE and the broader trial literature and arrived at the same place.

The science, at the level of evidence we actually trust, does not support the idea that TRT raises heart attack risk in men who are appropriately screened and monitored.

But there is a part of the TRAVERSE data that deserves attention because it does not get talked about enough in the simple version of this story.

The trial found that men on testosterone had higher rates of atrial fibrillation, a type of irregular heart rhythm, as well as higher rates of pulmonary embolism, which is a blood clot in the lungs, and a higher rate of acute kidney injury compared to placebo. These were secondary findings, not the primary outcome, but they were real and they were statistically significant. The atrial fibrillation rate was 3.5 percent in the testosterone group versus 2.4 percent in placebo. Pulmonary embolism was 0.9 percent versus 0.5 percent.

This is where the monitoring piece becomes more than just a recommendation.

Testosterone increases the production of red blood cells by stimulating something called erythropoiesis, which is the process your body uses to make new red blood cells, and more red blood cells mean thicker blood, and thicker blood clots more easily. The measure that tracks this is called hematocrit, which is simply the percentage of your blood volume that is made up of red blood cells. Normal is roughly 38 to 50 percent for men. When hematocrit climbs above 54 percent on TRT, the clotting risk becomes real and measurable, and that is the threshold where most clinicians will either reduce the dose, have the patient donate blood, or pause the protocol entirely.

The men who end up with clotting events on TRT are rarely the ones whose doctors caught the rising hematocrit at the six-month lab check. They are the ones who stopped getting labs.

The lipid picture on TRT is also worth understanding rather than dismissing. Testosterone tends to lower HDL, which is the type of cholesterol associated with clearing buildup from artery walls, and the degree of that drop depends on the dose and the form of testosterone being used. It is not dramatic in most cases, but if a man's LDL is already elevated and his diet is high in saturated fat and he stops doing cardio because he feels better on testosterone, those things compound each other in a direction you do not want.

The injection is not the intervention. The injection is one variable inside a larger system.

What the TRAVERSE trial actually proved is that testosterone, when used in men with properly confirmed low levels and managed with appropriate follow-up, does not add cardiovascular risk on top of whatever risk those men already carry from their age, their metabolic health, and their lifestyle. That is a different and much more precise claim than "TRT is safe," and the difference matters because the men who run into trouble on TRT are almost always the ones who treated the diagnosis as the end of the story rather than the beginning of an ongoing system to manage.

The fear was wrong. But the complacency it sometimes gets replaced with is its own kind of problem.

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References

1. Lincoff AM, et al. 2023. "Cardiovascular Safety of Testosterone-Replacement Therapy." New England Journal of Medicine. Source
2. Zitzmann M, et al. 2026. "Cardiovascular Safety of Testosterone Therapy: Insights from the TRAVERSE Trial and Beyond." Andrology. Source
3. Hudson J, et al. 2024. "Long-term Cardiovascular Safety of Testosterone-Replacement Therapy in Middle-Aged and Older Men: A Meta-Analysis of Randomized Controlled Trials." JACC. 04050-6 Source

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