Is TRT Safe for Your Heart? 2026 Research Finally Answers

For a decade, one question followed every man considering testosterone replacement therapy: will it give me a heart attack? A 2013 Veterans Affairs study suggested it might. A 2014 FDA warning amplified the fear. Then in June 2023, the largest randomized cardiovascular safety trial ever conducted on testosterone — the TRAVERSE trial — published its results in the New England Journal of Medicine. The short answer: in men with confirmed low testosterone and existing cardiovascular risk, testosterone replacement therapy did not increase the rate of heart attacks, strokes, or cardiovascular death compared to placebo.

The longer answer is more useful. TRAVERSE did flag three specific signals atrial fibrillation, pulmonary embolism, and acute kidney injury — and it left several populations unstudied. This article walks through what the testosterone replacement therapy heart risk picture actually looks like in 2026: the data, the critiques, the 2026 European Expert Panel position, and what your monitoring plan should include before and during therapy. This is a companion piece to the full guide to testosterone replacement therapy and pairs with the deeper dives on TRT side effects and types of TRT.

The TRAVERSE trial: what it tested and what it found

TRAVERSE — short for “Testosterone Replacement Therapy for Assessment of Long-term Vascular Events and Efficacy Response in Hypogonadal Men” — is the randomized, placebo-controlled study the FDA required manufacturers to run after its 2015 safety labeling action. The study enrolled 5,246 men aged 45 to 80 who met three criteria:

Symptoms of hypogonadism
Two morning testosterone measurements below 300 ng/dL
Either established cardiovascular disease or multiple cardiovascular risk factors

Participants received either daily transdermal 1.62% testosterone gel or a matched placebo gel for a mean of 21.7 months (roughly 22 months). Testosterone doses were titrated to maintain serum levels between 350 and 750 ng/dL (12–26 nmol/L). The primary composite endpoint — known as MACE, for “major adverse cardiovascular events” combined three outcomes: death from cardiovascular causes, non-fatal myocardial infarction, and non-fatal stroke.

The primary result: testosterone was non-inferior to placebo. The event rate was 7.0% in the testosterone group versus 7.3% in the placebo group. For a population specifically enriched for cardiovascular risk, that’s the best-designed test of testosterone replacement therapy heart risk ever conducted — and it came back reassuring on the biggest question.

Secondary efficacy signals also favored testosterone: new-onset diabetes dropped by roughly 22.5% in the treatment group, and improvements were seen in exual desire, depressive symptoms, and correction of anemia.

The three signals TRAVERSE did flag

Non-inferiority on MACE doesn’t mean zero cardiovascular concern. TRAVERSE identified three specific events that occurred more often in the testosterone group than the placebo group.

Atrial fibrillation

91 men on testosterone developed AFib (3.5%) versus 63 on placebo (2.4%). In absolute terms, that’s about one additional case of AFib per 100 men treated over 22 months. AFib is rarely life-threatening on its own, but it raises stroke risk if untreated, which is why the signal matters even when MACE looked neutral. If you already have AFib, an arrhythmia, or structural heart disease, your clinician should factor this in.

Pulmonary embolism

0.9% of testosterone-treated men versus 0.5% on placebo experienced a PE — roughly four additional cases per 1,000 men treated. Pulmonary embolism is a clot that travels to the lungs and can be life-threatening. The mechanism is biologically plausible: testosterone raises red blood cell production (hematocrit), and higher hematocrit increases blood viscosity. Men with prior deep vein thrombosis, clotting disorders, or recent prolonged immobilization need individualized assessment.

Acute kidney injury

2.3% of testosterone-treated men experienced acute kidney injury versus 1.5% on placebo. Most episodes were transient, but the signal is real. Baseline kidney function (eGFR) should be established before starting therapy and monitored during it.

None of these signals individually was large enough to cross the non-inferiority threshold for MACE, but together they define what monitoring should target. A 2024 post-hoc analysis of TRAVERSE found that rising hematocrit during therapy was not directly correlated with MACE — suggesting the clot signal comes from other mechanisms, likely including androgen effects on coagulation pathways.

Why the TRAVERSE verdict isn’t fully settled

TRAVERSE is the best evidence available, but it isn’t perfect. A detailed critique published in JACC: Advances — titled “Is it the TRAVERSE Trial or a Travesty?” — laid out the three limitations readers should know. First, the discontinuation rate. 61.4% of testosterone participants and 61.7% of placebo participants stopped their assigned therapy during the trial. That’s an extraordinarily high dropout, and it means the comparison for much of the follow-up was effectively testosterone-stopped versus placebo-stopped, not testosterone versus placebo. Some of the non-inferiority finding may reflect that many participants weren’t actually being treated by the end.

Second, under-repletion. About 25% of men in the testosterone arm never reached the normal testosterone range. The median increase from baseline was only 9.3 to 12.9 nmol/L — meaningful, but not full replacement. If the treatment was under-dosed for a quarter of patients, the safety signal is partly a test of a partially-treated group. Third, loss to follow-up. Roughly 18% of participants were lost to follow-up — a rate considered high by modern RCT standards. And a fourth limitation, noted by the 2026 European Expert Panel: the study population was older (mean age 63) and explicitly high-risk. Findings don’t cleanly transfer to a hypogonadal 38-year-old with no cardiovascular disease.

Here’s how the testosterone cardiovascular safety picture has evolved across three eras of evidence:

Dimension	Pre-TRAVERSE observational data (pre-2023)	TRAVERSE RCT (2023)	Post-TRAVERSE synthesis (2024–2026)
Evidence type	Observational cohorts, VA registries	Randomized, placebo-controlled, double-blind	RCT + meta-analyses + expert position statements
Sample size	Hundreds to ~9,000 (mixed quality)	5,246 men	Cumulative >20,000 across analyses
MACE signal	Mixed — some signals of harm, others neutral	Non-inferior to placebo	Non-inferior confirmed; March 2026 EAU data suggests possible benefit in hypogonadal men with CV disease
AFib signal	Not consistently tracked	3.5% vs 2.4% (91 vs 63 cases)	Confirmed as real signal; pre-screening recommended
VTE / PE signal	Case reports, inconsistent	0.9% vs 0.5%	Real but absolute risk small
Who benefits most	Unclear	Hypogonadal men 45–80 with CV risk	Hypogonadal men with confirmed low T and symptoms
Regulatory posture	2015 FDA caution label	FDA-mandated trial fulfilled	Experts urging label revision

The men TRAVERSE did not include

A clean reading of TRAVERSE requires a clean reading of who was excluded — because the safety findings don’t automatically generalize.

TRAVERSE did not enroll men with:

Myocardial infarction, stroke, or coronary revascularization in the prior 3 months (extended to 6 months by subsequent American College of Cardiology and Endocrine Society guidance for clinical practice)
Uncontrolled heart failure
Severe, untreated sleep apnea
Hematocrit above 50% at baseline
Active prostate cancer or untreated severe BPH
Men under 45
Men without confirmed biochemical hypogonadism

If you had a heart attack two months ago, TRAVERSE is not your trial — the expert recommendation is to wait at least six months after an acute cardiovascular event before initiating TRT, and to do so only with cardiology co-management. If you’re 38 with borderline low testosterone and no cardiovascular disease, TRAVERSE’s data doesn’t address you directly either; your risk/benefit is weighed differently, and fertility considerations (covered in the TRT and fertility guide) may dominate the decision.

This is also the core of trial-chair Steven Nissen’s widely-quoted caveat: TRAVERSE’s safety findings should not be used to justify prescribing testosterone to men who don’t have documented hypogonadism.

What the 2026 European Expert Panel concluded

In 2026, the European Expert Panel for Testosterone Research published a position statement in Andrology synthesizing TRAVERSE with subsequent meta-analyses and registry data. Their three core conclusions: First, testosterone therapy, when prescribed to appropriately selected patients with confirmed hypogonadism and monitored regularly, does not meaningfully increase cardiovascular event risk. The MACE non-inferiority finding is considered robust and clinically reliable for the population studied.

Second, hematocrit is the single most important on-therapy parameter to monitor, and clinicians should target levels below 54% and reduce dose or pause therapy if levels exceed that threshold. Third, the TRAVERSE under-repletion and high discontinuation limitations, while real, do not invalidate the top-line safety conclusion — they suggest the trial may have understated the actual benefit of adequately-dosed, well-monitored therapy.

A separate analysis presented at the European Association of Urology Congress in March 2026 found that in men under 55 with hypogonadism and cardiovascular disease, appropriately-dosed testosterone therapy was associated with reduced cardiovascular mortality over 10 years — a signal consistent with observational data from the post-2023 period. That finding is observational, not randomized, and should not be over-read, but it reinforces that for the right patient the balance is favorable. The FDA’s 2015 cautionary labeling has not yet been formally revised, though expert groups are actively petitioning for it.

What your doctor should be checking before and during TRT

The point of knowing the TRAVERSE signals is using them to structure monitoring. A complete cardiovascular-risk-aware TRT protocol should include the following:

Baseline cardiovascular workup: Blood pressure, resting ECG, fasting lipid panel, HbA1c, and a cardiovascular risk score (ASCVD or equivalent). For men over 50 or with any risk factor, a coronary artery calcium (CAC) score is a low-cost way to stratify intermediate-risk patients before starting therapy.
Baseline hematocrit and CBC: A starting hematocrit above 50% is a contraindication to starting TRT without investigation. Below 50%, it becomes your reference point.
Baseline kidney function: eGFR and serum creatinine — because of the TRAVERSE acute kidney injury signal.
Confirmed biochemical hypogonadism: Two morning total testosterone measurements, taken at least a week apart, below the reference range — typically below 300 ng/dL. Single low readings are not enough.
Hematocrit monitoring at 3, 6, and 12 months, then every 6 months: If hematocrit climbs above 52%, your clinician should reduce dose, switch formulation, or consider therapeutic phlebotomy. Above 54%, pausing therapy is the standard response.
Symptom screen for AFib and clotting events at every visit: New-onset palpitations, unexplained leg swelling, chest pain, or sudden shortness of breath should trigger evaluation.
Annual repeat of the baseline cardiovascular workup: Lipids, blood pressure, HbA1c, and a reassessment of cardiovascular risk.

If your prescriber whether a telehealth clinic or a physical practice — isn’t doing at least items 1, 2, 4, and 5, that’s a flag. The TRT cost guide goes deeper into how to tell which telehealth providers run full monitoring protocols and which do not.

Frequently asked questions about TRT and heart risk

Does testosterone therapy increase heart attack risk?

Based on the 2023 TRAVERSE randomized trial of 5,246 men at elevated cardiovascular risk, testosterone replacement therapy did not increase the incidence of heart attacks, strokes, or cardiovascular death compared to placebo over an average of 22 months. The trial was designed specifically to answer this question for men with confirmed hypogonadism, and the finding is considered robust for that population.

Who should not take testosterone replacement therapy?

Men with a heart attack, stroke, or coronary revascularization in the prior six months; men with uncontrolled heart failure; men with a baseline hematocrit above 50%; men with active or untreated prostate cancer; men with severe untreated sleep apnea; and men without documented low testosterone on two confirmatory tests. Men in active fertility planning should also consider alternatives — TRT suppresses sperm production.

Can TRT cause atrial fibrillation?

TRAVERSE found a small but statistically significant increase in atrial fibrillation — 3.5% on testosterone versus 2.4% on placebo. That’s roughly one extra case per 100 men treated over 22 months. If you have existing AFib, structural heart disease, or a strong family history, discuss the signal specifically with your clinician. For men without those risk factors, the absolute increase is small but worth knowing about.

Does testosterone therapy cause blood clots or pulmonary embolism?

TRAVERSE identified a small increase in pulmonary embolism — 0.9% on testosterone versus 0.5% on placebo. The mechanism likely includes testosterone’s effect on red blood cell production, which raises hematocrit and blood viscosity. Men with a history of DVT or a known clotting disorder should be evaluated carefully before starting therapy and monitored more closely during it.

Is TRT safe if I’ve already had a heart attack?

TRAVERSE excluded men who had a cardiovascular event within three months of enrollment. The standard clinical guidance — from the American College of Cardiology and the Endocrine Society — is to wait at least six months after a heart attack, stroke, or revascularization before starting or restarting TRT, and to do so in coordination with a cardiologist. Beyond that window, TRT is not automatically contraindicated for men with stable cardiovascular disease and confirmed hypogonadism.

What heart tests should I have before and during TRT?

Before starting: blood pressure, resting ECG, fasting lipid panel, HbA1c, baseline hematocrit and CBC, eGFR and serum creatinine, and two morning testosterone measurements. Consider a coronary artery calcium score if you have intermediate cardiovascular risk. During therapy: repeat hematocrit at 3, 6, and 12 months, then every six months; annual lipid panel, blood pressure, and HbA1c; and evaluation of any new palpitations, leg swelling, chest pain, or shortness of breath.

How does hematocrit relate to TRT heart risk?

Testosterone stimulates red blood cell production, which raises hematocrit. Above about 54%, the thicker blood may contribute to clot risk. Standard practice is to monitor hematocrit every three to six months during therapy, reduce dose if it climbs above 52%, and pause therapy if it exceeds 54%. Therapeutic phlebotomy (regulated blood draw) is sometimes used. Notably, a TRAVERSE sub-analysis did not find a direct link between rising hematocrit and MACE, but the relationship to clot events is still considered clinically important.

Do TRAVERSE results apply to men under 45?

TRAVERSE enrolled only men aged 45 to 80. The trial’s findings don’t formally extend to younger men. For men under 45 with confirmed hypogonadism and no cardiovascular disease, the baseline cardiovascular risk is low, so the absolute risks identified in TRAVERSE are likely even smaller — but fertility implications become more important, and non-TRT alternatives (clomiphene, HCG, lifestyle) are often considered first.

The bottom line on TRT and your heart

The TRAVERSE trial settled the biggest question: in men aged 45 to 80 with confirmed hypogonadism and elevated cardiovascular risk, testosterone replacement therapy does not raise the rate of heart attacks, strokes, or cardiovascular death. That resolves a decade of uncertainty driven by weaker observational data. What remains is the smaller-but-real picture: atrial fibrillation, pulmonary embolism, and acute kidney injury signals that should shape monitoring rather than disqualify therapy, and patient populations — post-acute-event men, younger men, men without documented hypogonadism — where the trial’s findings don’t directly apply.

Talk to a board-certified endocrinologist or urologist to confirm hypogonadism with two morning testosterone tests, review your cardiovascular history, and build a monitoring plan that tracks your hematocrit, blood pressure, and lipids every three to six months while you’re on therapy.