If you have done any research on testosterone therapy — or talked to a friend who has — you have probably heard some version of “isn’t that dangerous for your heart?” or “doesn’t it cause prostate cancer?”
Those concerns are not unreasonable. They come from real questions doctors have asked for decades. But medicine has actually answered most of them now, with large, well-designed studies. Here is what the evidence says — the good news, the real risks, and the parts that are still being worked out.
“Isn’t testosterone bad for your heart?”
This is the single most common worry, and it is the one with the most reassuring recent evidence. In 2023, the largest study ever conducted on testosterone therapy — over 5,200 men, followed for more than two years — set out specifically to answer this question. The result: men on physician-supervised testosterone therapy had no higher rate of heart attack, stroke or cardiovascular death than men on placebo.1 Based on this and other data, the FDA removed its cardiovascular warning label from testosterone products in 2025.
That said, the same study did find a couple of things worth knowing honestly. Men on testosterone had a slightly higher rate of irregular heart rhythms, including atrial fibrillation, and a small increase in blood clot events. Neither of these translated into more heart attacks or strokes overall, but they are part of why ongoing monitoring — not a one-time prescription — is part of responsible care.
“Doesn’t testosterone cause prostate cancer?”
This idea dates back to a single study from 1941 and has been one of the most persistent myths in men’s health. Modern, carefully controlled research tells a different story: in the same large 2023 trial, prostate cancer occurred at nearly identical rates in the testosterone and placebo groups — a difference so small it was not statistically meaningful.2 A larger analysis pooling 41 separate clinical trials came to the same conclusion in 2026.3
Regulators have been moving in the same direction. In December 2025 an FDA advisory panel recommended removing outdated prostate-cancer warnings from testosterone labeling, and by mid-2026 federal health officials had formally requested that change be made.9,10
This does not mean prostate health is ignored — quite the opposite. Part of physician-supervised care is a PSA blood test and prostate check before starting, and periodic rechecks during treatment, which is exactly how the men in these studies were followed.
Blood clots
This is a real, if uncommon, consideration. A pooled analysis of 13 clinical trials did not find a statistically significant increase in blood clot risk with testosterone therapy, but the researchers were upfront that their data could not completely rule out a modest increase either.4 The FDA has included a general blood clot warning on testosterone products since 2014.
What we now understand is that most of this risk traces back to one specific, very manageable lab value: your red blood cell count. Which is exactly why we check it.
The one real, common side effect: thicker blood
If there is one thing the research is clearest about, it is this one. Testosterone therapy increases red blood cell production, and in some men that raises the blood count, or hematocrit, more than is healthy. This is the most frequently observed lab change in testosterone studies — far more common than any of the scarier headlines you may have read.5
Left unchecked, it can raise the risk of clotting. Managed well, it is simple: we check your blood count before starting and at regular intervals afterward, and adjust your dose — or occasionally recommend donating blood — if it climbs too high. This single monitoring step addresses most of the clotting concern above.
Fertility: the trade-off most men don’t expect
This one surprises a lot of men. Testosterone therapy tells your brain that testosterone levels are already high, which can shut down your body’s own sperm production — sometimes significantly. For most men this reverses within several months to about a year after stopping treatment, though the timeline varies and, in rarer cases involving long-term or high-dose use, recovery can be incomplete.7
If you are planning to have children in the near future, this is a conversation to have with your physician before starting. There are alternative approaches that can raise your testosterone while protecting fertility.
Smaller things worth knowing
- Skin changes. Acne or oilier skin are the most commonly reported side effects, usually mild.
- Breast tenderness or enlargement. Uncommon, and manageable if it happens.
- Sleep apnea. Very high, unsupervised doses have worsened sleep apnea in some studies. Properly dosed and monitored therapy has not shown this effect, and some men’s sleep actually improves.8
- Blood pressure. Recent evidence has prompted updated labeling, which is one more reason we check it.
- Cholesterol. A small drop in HDL, the “good” cholesterol, has been observed in trials.
The bottom line
The two things men worry about most — heart disease and prostate cancer — have turned out, in the largest and best-designed studies we have, not to be significantly increased by physician-supervised testosterone therapy. The real, documented risks are quieter and more manageable: blood count changes, a modest clotting signal, and a fertility trade-off for men not done building their family.
None of these are reasons to be afraid of treatment. They are reasons to do it with monitoring, bloodwork, and a physician who takes your safety as seriously as your results.
Have questions about whether these risks apply to you specifically? That is exactly what your intake and lab work are for.
References
1. Lincoff AM, Bhasin S, Flevaris P, et al. Cardiovascular Safety of Testosterone-Replacement Therapy. N Engl J Med. 2023;389(2):107–117.
2. Bhasin S, Travison TG, Pencina KM, et al. Prostate Safety Events During Testosterone Replacement Therapy in Men With Hypogonadism: A Randomized Clinical Trial. JAMA Netw Open. 2023;6(12):e2348692.
3. Cardiovascular and prostate cancer risk associated to testosterone replacement therapy — a systematic review and meta-analysis of 41 randomized controlled trials. Int J Impot Res. 2026.
4. Testosterone replacement therapy and the risk of venous thromboembolism: a systematic review and meta-analysis of randomized controlled trials. Thromb Res. 2021.
5. Secondary Polycythemia in Men Receiving Testosterone Therapy Increases Risk of Major Adverse Cardiovascular Events and Venous Thromboembolism in the First Year of Therapy. J Urol.
6. Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(5):1715–1744.
7. Testosterone replacement therapy and spermatogenesis in reproductive age men. Nat Rev Urol. 2025.
8. Efficacy of testosterone replacement therapy on sleep disturbance among hypogonadal men without obstructive sleep apnea (EARTH study subanalysis). Aging Male. 2018;21(4):232–237.
9. HHS. HHS Announces Requested Updates to Testosterone Therapy Product Labels. News release, June 18, 2026.
10. Urology Times. Experts urge FDA to revisit labeling for testosterone replacement therapy in men. Coverage of the December 10, 2025 FDA advisory panel, 2026.
This article is for general education and is not a substitute for individualized medical advice. Testosterone therapy requires a physician evaluation, laboratory testing and ongoing monitoring, and carries risks as well as benefits. Regulatory guidance in this area continues to evolve; your physician can discuss the most current recommendations with you. Individual risk varies based on personal and family health history.
Certain treatments referenced on this site are compounded preparations or are prescribed for uses other than those approved by the FDA. Compounded medications are not FDA-approved and are not reviewed by the FDA for safety, effectiveness, or manufacturing quality. Your physician will review this with you before prescribing.
