Short answer: It may raise the risk. In TRAVERSE, the largest testosterone trial, atrial fibrillation occurred in 3.5% of men on testosterone gel and 2.4% on placebo, and the AndroGel 1.62% and Xyosted labels now list it. Heart attacks, strokes and heart deaths were not more common. A later real-world study found a similar but not statistically significant rise.
TRAVERSE enrolled 5,246 men aged 45 to 80 with low testosterone and heart disease or high heart risk, and gave them 1.62% testosterone gel or placebo gel, with the dose adjusted to keep testosterone between 350 and 750 ng/dL (Lincoff 2023). Mean follow-up was 33 months. Its main question was heart attacks, strokes and heart deaths: 7.0% on testosterone and 7.3% on placebo, which met the bar for not worse than placebo. The paper also reported more atrial fibrillation, acute kidney injury and pulmonary embolism in the testosterone group.
| Event | Testosterone gel | Placebo |
|---|---|---|
| Non-fatal arrhythmias needing treatment | 5.2% | 3.3% |
| Atrial fibrillation | 3.5% | 2.4% |
| Acute kidney injury | 2.3% | 1.5% |
| Bone fracture | 3.5% | 2.5% |
A study of health records (Greenberg 2024) matched 2,134 men starting testosterone gel with 2,134 similar men who did not. Over 3 years the relative risk of new atrial fibrillation was 1.48, but the range was wide (0.93 to 2.37) and not statistically significant. Kidney injury was significantly higher (relative risk 1.53). Men given testosterone started lower, at 207 against 246 ng/dL on average. The authors called for more studies. Record-based studies can miss differences between the groups.
The AndroGel 1.62% label also reports more clots in the legs or lungs on testosterone in TRAVERSE, 1.7% against 1.2% (section 5.3); see blood clots on TRT. TRAVERSE used daily gel in men with heart risk, so neither source shows the rate with injections or in younger, healthier men.
Atrial fibrillation is a fast, irregular rhythm in the upper chambers of the heart. MedlinePlus says some people do not notice it. When there are symptoms, they can include a racing, pounding, fluttering or irregular pulse, palpitations, dizziness or fainting, tiredness, weakness, shortness of breath, and chest pain or pressure. Chest pain or pressure is an emergency.
MedlinePlus lists common causes too: heavy drinking, high blood pressure, heart disease, an overactive thyroid and some medicines.
A man with past atrial fibrillation, other rhythm problems or heart disease can ask how the TRAVERSE result applies to him, and what symptoms should prompt a call. Logging palpitations or a racing pulse in Dose Track, with the date and the dose before it, gives the prescriber a clear record.
Read more on Dose Track: Low testosterone · AndroGel side effects · TRT hematocrit monitoring · Hazard ratio