Does TRT Cause Atrial Fibrillation? What TRAVERSE, the FDA Label and the Heart Rhythm Studies Show in Men Over 40

In TRAVERSE, atrial fibrillation occurred in 3.5% of men on testosterone gel and 2.4% on placebo. Yet in a VA cohort, men whose levels normalized on TRT had less AF. Here is how both findings can be true.

Does TRT cause atrial fibrillation? Testosterone therapy is linked to a small rise in atrial fibrillation (AF) in the best trial data, but the full picture is more mixed than a yes or no. In the TRAVERSE trial, atrial fibrillation occurred in 3.5% of men on testosterone gel and 2.4% of men on placebo, according to the FDA-approved AndroGel 1.62% label. The same trial found no increase in heart attacks or strokes.

Other research points the opposite way. A large Veterans Affairs study found less atrial fibrillation in men whose testosterone returned to normal on treatment, and several population studies tie low natural testosterone to more AF. A newer reading of all this data is that the relationship is U-shaped: AF risk seems higher at both ends of the testosterone range. This article goes through the trial, the cohort studies and what a man over 40 can do with the information.

TRT has not been proven to cause atrial fibrillation, but the strongest randomized evidence shows a modest increase. TRAVERSE recorded more AF on testosterone than on placebo, and a large 2025 cohort study found the same direction. Meta-analyses of smaller trials and a TRAVERSE-style real-world replication did not find a significant increase. No trial so far has made atrial fibrillation its main outcome, which a 2026 review in the World Journal of Men's Health points out is the reason the debate continues.

Atrial fibrillation is an irregular, often fast heartbeat that starts in the heart's upper chambers. According to the National Heart, Lung, and Blood Institute (NHLBI), AF that is undiagnosed or left untreated can cause stroke and heart failure. That is why even a small shift in AF risk matters more than its size suggests.

TRAVERSE found a higher incidence of atrial fibrillation in men on testosterone than in men on placebo. The trial (Lincoff and colleagues, New England Journal of Medicine, 2023) enrolled 5246 men aged 45 to 80 with heart disease or a high risk of it, symptoms of hypogonadism and two fasting testosterone readings below 300 ng/dL. Men applied daily 1.62% testosterone gel, adjusted to keep levels between 350 and 750 ng/dL, or a placebo gel. Mean treatment lasted 21.7 months and mean follow-up was 33.0 months.

TRAVERSE was built to test major cardiac events. A heart attack, stroke or cardiovascular death occurred in 182 men (7.0%) on testosterone and 190 men (7.3%) on placebo, a hazard ratio of 0.96. The NEJM abstract adds that a higher incidence of atrial fibrillation, acute kidney injury and pulmonary embolism was observed in the testosterone group. Our TRAVERSE heart attack and stroke guide covers the cardiac result in detail.

The FDA label for AndroGel 1.62% gives the exact rates. Among adverse reactions reported in TRAVERSE at more than 2% in either group and higher on testosterone, it lists nonfatal arrhythmias warranting intervention (5.2% vs 3.3%), atrial fibrillation (3.5% vs 2.4%), acute kidney injury (2.3% vs 1.5%) and bone fracture (3.5% vs 2.5%). In plain terms, about one extra man in every hundred developed AF on testosterone over the study period.

Low natural testosterone is linked to more atrial fibrillation in several population studies, especially in older men. In the Framingham Heart Study (Magnani and colleagues, Circulation: Arrhythmia and Electrophysiology, 2014), 275 of 1251 men developed AF over 10 years. In men aged 55 to 69, each 1 standard deviation drop in testosterone carried a hazard ratio of 1.30 for AF. In men aged 80 or older, the hazard ratio was 3.53. The link did not reach significance in men aged 70 to 79.

The Finnish FINRISK study (Zeller and colleagues, European Journal of Preventive Cardiology, 2018) followed 3876 men for a median of 13.8 years. Higher testosterone was associated with a lower risk of AF or ischaemic stroke in men, with a hazard ratio of 0.98 per 1 nmol/l increase. The UK Biobank analysis of 173,498 men (Xu and colleagues, Journal of Clinical Endocrinology and Metabolism, 2024) found 11,368 new AF cases over 11 years, and the lowest testosterone category carried a hazard ratio of 1.06 compared with the third quartile.

High-normal natural testosterone is also linked to more atrial fibrillation, which is the other half of the U-shape. In a post-hoc analysis of the ASPREE study (Tran and colleagues, EClinicalMedicine, 2024), 4570 healthy men aged 70 or older were followed for a median of 4.4 years, and 286 developed AF. Men in the top two testosterone quintiles had hazard ratios of 1.91 and 1.98 compared with the middle quintile. Baseline testosterone was 17.0 nmol/L in men who developed AF versus 15.7 nmol/L in those who did not.

The US ARIC study (Berger and colleagues, Maturitas, 2019) found the same direction in 9282 participants followed for a mean of 13.7 years. Men in the highest testosterone quartile had a hazard ratio of 1.33 for AF compared with the lowest. UK Biobank found that higher calculated free testosterone was linked to AF too (hazard ratio 1.07), alongside its finding for low total testosterone.

Some studies show TRT lowers AF risk when treatment brings testosterone back into the normal range rather than above it. Sharma and colleagues (Journal of the American Heart Association, 2017) studied 76,639 veterans with low testosterone. Men whose levels normalized on TRT had a lower AF risk than men on TRT whose levels did not normalize (hazard ratio 0.90) and than men who never received TRT (hazard ratio 0.79). TRT without normalization was not significantly different from no treatment (hazard ratio 0.89).

Real-world data on the other side are mixed. Bonnet and colleagues (European Journal of Endocrinology, 2025) compared 117,908 hypogonadal men on testosterone with matched untreated men in the TriNetX network. Over 5 years, testosterone was linked to more AF (hazard ratio 1.27) and fewer heart attacks (hazard ratio 0.94). Greenberg and colleagues (Journal of Sexual Medicine, 2024) built a TRAVERSE-like cohort of 2134 matched men per group and found no significant AF increase within 3 years (relative risk 1.48, 95% CI 0.93 to 2.37), while acute kidney injury did rise.

Corona and colleagues (Expert Opinion on Drug Safety, 2024) pooled 106 placebo-controlled trials with 8,126 men on testosterone and 7,310 on placebo. The AF increase seen in the one trial designed around cardiovascular safety was not confirmed across the others, with an odds ratio of 1.44 and a wide interval of 0.46 to 4.46. Most of those trials were small and short, so they had little power to detect a rare rhythm problem.

A U-shaped relationship between testosterone and atrial fibrillation is the reading that best fits the current data. A 2026 review by Maligireddy and colleagues in the Journal of the Endocrine Society concluded that converging evidence supports a U-shaped link, where both low and high testosterone raise AF risk. The review describes mechanistic work in which low testosterone disrupts calcium handling in heart cells, while high testosterone alters potassium currents. Much of that mechanism comes from laboratory and animal research, so it explains the pattern rather than proving it in people.

This framing also reconciles the conflicting studies. The VA men who benefited were those whose testosterone was restored to normal. The ASPREE and ARIC findings concern men with naturally high-normal levels. TRAVERSE targeted 350 to 750 ng/dL, which sits within the normal range, so its AF signal is harder to explain by overshooting alone. The same review recommends risk-stratified TRT, mid-physiologic testosterone targets, stable formulations and structured monitoring until better data arrive.

The FDA label for AndroGel 1.62% lists the TRAVERSE atrial fibrillation and arrhythmia rates in its adverse reactions section. In February 2025 the FDA issued class-wide labeling changes for testosterone products. It removed Boxed Warning language about increased risk of adverse cardiovascular outcomes, added the TRAVERSE results to all testosterone products, added blood pressure warnings and kept the limitation of use for age-related hypogonadism.

Blood pressure matters here because high blood pressure is a common driver of AF. In TRAVERSE, mean systolic blood pressure rose 1.0 mm Hg from baseline to 36 months on testosterone gel and fell 0.5 mm Hg on placebo, a between-group difference of 1.5 mm Hg, according to the label. That is a small average change, but it is one reason a home blood pressure baseline is worth having before starting therapy. Our guide to blood pressure for men over 40 explains how to take accurate home readings.

The warning signs of atrial fibrillation on TRT are the same as AF in anyone: fatigue, palpitations, breathlessness, chest pain and dizziness. The NHLBI lists fatigue as the most common symptom and describes palpitations as the feeling that the heart is skipping a beat, fluttering, pounding, or beating too hard or too fast. AF can also occur with no symptoms at all, which makes it easy to miss.

• Unusual tiredness that does not match your training load or sleep.
• A fluttering, racing or irregular pulse, especially at rest.
• Breathlessness when exercising or lying down.
• Dizziness, light-headedness or fainting.
• Chest pain, which needs urgent medical care regardless of cause.

Men over 40 on TRT can manage AF risk by treating only a confirmed deficiency, aiming for the middle of the normal range and watching for rhythm symptoms. The observational data point to higher AF risk at both ends of the range, though TRAVERSE still saw a small AF rise with levels held in the normal range, so mid-range targets and monitoring are sensible rather than a guarantee. None of the studies above tested a specific monitoring schedule for AF, so the steps below reflect the review's recommendations and general heart care rather than trial-proven protocols.

Lifestyle factors that raise AF risk independently of testosterone are worth handling at the same time. Our guides to alcohol and testosterone and to sleep apnea in men cover two of the common ones. This article is for educational purposes only and is not medical advice. It does not diagnose, treat, cure or prevent any disease. Chest pain, fainting or a racing irregular heartbeat needs prompt medical attention whether or not you use testosterone.

• Lincoff AM et al. Cardiovascular Safety of Testosterone-Replacement Therapy (TRAVERSE). New England Journal of Medicine, 2023. https://doi.org/10.1056/NEJMoa2215025
• AndroGel (testosterone gel) 1.62% prescribing information, adverse reactions and blood pressure sections. DailyMed, US National Library of Medicine, 2025. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=f4e8d29b-8707-4d47-e053-2a95a90aecee
• US Food and Drug Administration. FDA issues class-wide labeling changes for testosterone products, February 2025. https://www.fda.gov/drugs/drug-alerts-and-statements/fda-issues-class-wide-labeling-changes-testosterone-products
• Magnani JW et al. Association of sex hormones, aging, and atrial fibrillation in men: the Framingham Heart Study. Circulation: Arrhythmia and Electrophysiology, 2014. https://doi.org/10.1161/CIRCEP.113.001322
• Zeller T et al. Low testosterone levels are predictive for incident atrial fibrillation and ischaemic stroke in men, but protective in women: results from the FINRISK study. European Journal of Preventive Cardiology, 2018. https://doi.org/10.1177/2047487318778346
• Berger D et al. Plasma total testosterone and risk of incident atrial fibrillation: The ARIC study. Maturitas, 2019. https://doi.org/10.1016/j.maturitas.2019.03.015
• Xu B et al. Associations of Serum Testosterone and Sex Hormone-binding Globulin With Incident Arrhythmias in Men From UK Biobank. Journal of Clinical Endocrinology and Metabolism, 2024. https://doi.org/10.1210/clinem/dgad526
• Tran C et al. Testosterone and the risk of incident atrial fibrillation in older men: further analysis of the ASPREE study. EClinicalMedicine, 2024. https://doi.org/10.1016/j.eclinm.2024.102611
• Sharma R et al. Normalization of Testosterone Levels After Testosterone Replacement Therapy Is Associated With Decreased Incidence of Atrial Fibrillation. Journal of the American Heart Association, 2017. https://doi.org/10.1161/JAHA.116.004880
• Bonnet F et al. Testosterone therapy and the risk of atrial fibrillation, venous thromboembolism and cardiovascular events in cis men with hypogonadism and trans men. European Journal of Endocrinology, 2025. https://doi.org/10.1093/ejendo/lvaf183
• Greenberg DR et al. Association of testosterone replacement therapy with atrial fibrillation and acute kidney injury. Journal of Sexual Medicine, 2024. https://doi.org/10.1093/jsxmed/qdae138
• Traish AM et al. Does Testosterone Therapy Increase Risk of Atrial Fibrillation? Appraisal of the Contemporary Scientific and Clinical Evidence. World Journal of Men's Health, 2026. https://doi.org/10.5534/wjmh.260004
• Corona G et al. Cardiovascular safety of testosterone replacement therapy in men: an updated systematic review and meta-analysis. Expert Opinion on Drug Safety, 2024. https://doi.org/10.1080/14740338.2024.2337741
• Maligireddy AR et al. Association of testosterone and testosterone replacement therapy with atrial fibrillation: an updated review. Journal of the Endocrine Society, 2026. https://doi.org/10.1210/jendso/bvag180
• National Heart, Lung, and Blood Institute. Atrial Fibrillation: Symptoms. https://www.nhlbi.nih.gov/health/atrial-fibrillation/symptoms

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