For more than a decade, the question of whether testosterone replacement therapy is safe for the heart has hung over men’s health clinics. Some early studies suggested an increased risk of heart attack and stroke. Others suggested the opposite, that men with low testosterone might be at higher cardiovascular risk in the first place. The headlines have been confusing, and many men who could benefit from TRT have been left wondering whether they are trading low energy for a bigger heart attack.
The good news is that the science has moved forward. A large, well-designed trial called TRAVERSE, published in the New England Journal of Medicine in 2023, was specifically built to answer this question[1][2]. The results changed the conversation, and they are now the starting point for any honest discussion of TRT and cardiovascular safety.
This article walks through what we know, what TRAVERSE actually showed, and what it means for a man considering or already on testosterone therapy.
Why Did Cardiovascular Risk Become a Concern in the First Place?
The worry started with a handful of older studies. In 2010, a clinical trial of testosterone gel in older, frail men was stopped early because of more cardiovascular events in the treatment group. A few years later, two large observational studies suggested a higher rate of heart attacks in the months after men started testosterone therapy.
Those studies had real limitations. They were short, the men involved were often quite sick at baseline, and the data were not designed to isolate testosterone as the cause. Still, the FDA added a label warning to testosterone products in 2015, and many cardiologists became cautious about prescribing it.
For the next several years, clinicians and patients were stuck between two competing messages. On one hand, untreated low testosterone is itself associated with higher rates of obesity, diabetes, and cardiovascular disease. On the other hand, raising testosterone with medication might have its own risks. There was no large, dedicated trial to settle the question.
What Was the TRAVERSE Trial?
TRAVERSE stands for Testosterone Replacement Therapy for Assessment of Long-term Vascular Events and Efficacy Response in Hypogonadal Men. It was a randomized, double-blind, placebo-controlled trial that enrolled more than 5,200 middle-aged and older men with documented low testosterone and either existing cardiovascular disease or a high cardiovascular risk profile.
Half the men received daily testosterone gel. The other half received an identical-looking placebo. Researchers then followed both groups for an average of about two years to see what happened.
The primary outcome was a composite of cardiovascular death, non-fatal heart attack, and non-fatal stroke. In other words, the kind of events men and clinicians actually care about.
What Did TRAVERSE Find?
On the main question, the answer was reassuring. Major adverse cardiovascular events occurred in about 7% of men in the testosterone group and about 7% of men in the placebo group. The difference was not statistically meaningful, and the trial met its predefined criterion for non-inferiority. In plain language, testosterone therapy did not increase the rate of heart attacks, strokes, or cardiovascular deaths compared with placebo in men with hypogonadism.
This was the largest, most rigorous study ever conducted on the question, and the result has reshaped clinical practice. Major guidelines have been updated to reflect that, when used in men with genuine hypogonadism, TRT does not appear to raise cardiovascular risk.
The trial was not without findings worth taking seriously, however.
What Were the Secondary Findings?
Even though the main cardiovascular outcome was reassuring, TRAVERSE flagged a few signals that men and clinicians should not ignore.
Atrial fibrillation and other arrhythmias. Men in the testosterone group had a higher rate of non-fatal arrhythmias that required intervention, about 5.2% compared with 3.3% in the placebo group. Most of these were atrial fibrillation.
Pulmonary embolism and venous clots. Venous thromboembolic events, which include deep vein thrombosis and pulmonary embolism, occurred more often in the testosterone group, about 1.7% compared with 1.2%. The absolute increase was small, but it was statistically meaningful.
Acute kidney injury. A small but real increase in acute kidney injury was also seen in the testosterone group.
Fractures. Unexpectedly, men in the testosterone group had a slightly higher rate of fractures, even though testosterone is generally thought to support bone density. This finding has not been fully explained.
None of these signals undid the main reassuring result, but they are a reminder that no medication is risk-free.
What About Hematocrit, Estradiol, and Blood Pressure?
These are the day-to-day factors that most clinics monitor on TRT, and they remain important.
Hematocrit. Testosterone stimulates red blood cell production. If hematocrit rises above about 54%, blood becomes thicker, which can increase the risk of clots. Periodic blood counts are part of standard TRT monitoring, and dose adjustment or phlebotomy is used when hematocrit climbs too high.
Estradiol. Some testosterone is converted to estradiol. Both very low and very high estradiol have been linked to cardiovascular risk in observational data, which is one reason most clinics now monitor estradiol rather than blindly blocking it.
Blood pressure. TRT can cause a small rise in blood pressure for some men. The effect is usually mild but can matter in men whose blood pressure is already elevated.
A good clinic will check these numbers on a schedule rather than assuming everything is fine because the patient feels better.
Who Is at Higher Risk, and Who Should Be Cautious?
TRAVERSE enrolled men with significant cardiovascular risk to begin with. Even in that population, the main outcome was reassuring. However, certain situations call for more careful judgment.
Recent cardiovascular events. Men who have had a heart attack, stroke, or unstable angina within the previous several months are usually advised to wait before starting TRT.
History of atrial fibrillation. Given the arrhythmia signal in TRAVERSE, men with prior atrial fibrillation may need closer monitoring.
History of venous thromboembolism. Men with a personal or strong family history of clotting disorders should discuss the risks carefully with their clinician.
Untreated severe sleep apnea. Severe untreated sleep apnea can raise the risk of arrhythmias on its own. Treating the apnea first is usually wiser than starting TRT in parallel.
Polycythemia or already-high hematocrit. A baseline hematocrit close to the upper limit is a reason to start at a lower dose and monitor closely.
In each of these cases, TRT is not necessarily off the table, but the conversation needs to include the specific risk.
Does Treating Low Testosterone Actually Help the Heart?
This is the other side of the question, and it is still being studied. Low testosterone is associated with insulin resistance, central obesity, and higher rates of type 2 diabetes, which are all cardiovascular risk factors. Some studies have shown improvements in blood sugar control, body composition, and lipids with appropriate TRT, which could in theory translate into long-term cardiovascular benefit.
TRAVERSE was not designed to prove a cardiovascular benefit, only to test for harm. So while it is reasonable to expect some indirect benefit from treating low testosterone in men with metabolic problems, we should not overstate it. TRT is treatment for hypogonadism, not a heart medication.
What This Means for You
If you have symptoms of low testosterone, documented low levels on lab work, and you are otherwise a reasonable candidate, the current evidence supports TRT as a cardiovascularly safe treatment. The reassurance from TRAVERSE is genuine and represents a real shift from where the conversation was ten years ago[1][2].
That reassurance comes with a few practical conditions. Monitoring matters. Hematocrit, blood pressure, estradiol, and lipids should be checked on a schedule[3][4]. A history of arrhythmia, clotting, or recent cardiovascular events should be part of the conversation with your clinician. And TRT should not be used as a shortcut around lifestyle factors such as sleep, body composition, blood pressure control, and metabolic health, which are far more important for long-term cardiovascular risk than any single hormone.
The honest summary is this. Testosterone replacement therapy, used appropriately in men who actually need it, does not appear to raise the rate of heart attacks, strokes, or cardiovascular death[1][4]. It does come with smaller but real risks around arrhythmia and clotting that need monitoring. For most men with genuine hypogonadism, the benefits of properly managed TRT outweigh those risks.
If you are unsure where you fit, the right next step is not to read more headlines. It is to sit down with a clinician who is willing to look at your labs, your cardiovascular history, and your goals together, and to make a decision based on your numbers rather than on yesterday’s news.
References
- [1] Lincoff AM et al. Cardiovascular Safety of Testosterone-Replacement Therapy. N Engl J Med. 2023. PMID 37326322.
- [2] Lincoff AM et al. TRAVERSE trial full text. N Engl J Med. 2023. DOI 10.1056/NEJMoa2215025.
- [3] FDA. Class-wide labeling changes for testosterone products. February 28, 2025.
- [4] Long Term Cardiovascular Safety of Testosterone Therapy: A Review of the TRAVERSE Study. 2024. PMID 39344109.
