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Testosterone replacement therapy can be genuinely life-changing for men with diagnosed hypogonadism — but like any medical treatment, it comes with trade-offs. Understanding the potential side effects upfront isn't fear-mongering; it's what allows you to make an informed decision and work with your provider to stay safe. Here's what the evidence actually shows.
The Most Common Side Effect: Erythrocytosis
Erythrocytosis — an increase in red blood cell production — is the most common side effect of TRT and the one most likely to require intervention. Testosterone stimulates erythropoietin production, which increases red blood cell count. Mild increases are normal and often harmless, but hematocrit levels above 54% increase the risk of blood clots, stroke, and cardiovascular events. This is why regular blood monitoring is non-negotiable on TRT. If hematocrit rises too high, your provider may reduce your dose, adjust your injection frequency, or recommend therapeutic phlebotomy (blood donation). This side effect is dose-dependent — higher doses carry more risk.
Other Common Side Effects
Acne and oily skin are relatively common, particularly in the first few months as your body adjusts. This is essentially a repeat of the androgenic effects you experienced during puberty. Fluid retention can cause mild swelling and weight gain (typically 2–5 pounds of water weight). Sleep apnea may worsen in men who already have it — testosterone can affect upper airway anatomy and respiratory drive. Mood changes, while usually positive (improved energy and motivation), can occasionally include increased irritability or mood swings, particularly if dosing is inconsistent or supraphysiologic. Testicular atrophy occurs because exogenous testosterone signals your body to reduce its own production — the testes may shrink slightly. This is usually reversible upon discontinuation.
Key finding: The landmark TRAVERSE trial (2023) — the largest TRT cardiovascular safety study to date — found no significant increase in major adverse cardiovascular events (MACE) compared to placebo. The FDA subsequently updated labeling in 2025 to remove prior cardiovascular risk warnings, though it added new blood pressure monitoring recommendations.
Cardiovascular Safety: The TRAVERSE Trial Changed the Conversation
For years, there was concern that TRT increased cardiovascular risk. The TRAVERSE trial put this to rest for most patients: in over 5,000 men aged 45–80 followed for over 3 years, there was no statistically significant increase in heart attack, stroke, or cardiovascular death. However, the trial did note numerical (though not statistically significant) increases in atrial fibrillation, acute kidney injury, and pulmonary embolism. The practical takeaway: TRT doesn't appear to meaningfully increase major cardiovascular risk in appropriately selected patients, but it's not risk-free. Regular monitoring of blood pressure, hematocrit, and metabolic markers is essential. If you're interested in the broader connection between men's health and cardiovascular risk, our article on the ED-heart health connection covers related territory.
The Fertility Impact: This One's Important
TRT suppresses the hypothalamic-pituitary-gonadal axis, which means it significantly reduces — and can eliminate — sperm production. If you're on TRT and want to have children, this is a critical conversation to have with your provider before starting. Options include freezing sperm before starting treatment, using hCG (human chorionic gonadotropin) alongside TRT to maintain some testicular function, or using clomiphene citrate as an alternative that raises testosterone without suppressing fertility. This side effect is generally reversible, but recovery of sperm production can take 6–12 months or longer after stopping TRT.
What About Prostate Risk?
The historical concern that TRT causes prostate cancer has not been supported by modern evidence. Current guidelines do not consider TRT a cause of prostate cancer. However, testosterone can stimulate the growth of existing prostate tissue, so men with untreated or active prostate cancer should not use TRT. Regular PSA monitoring is recommended, with a baseline test before starting and periodic follow-ups. Any significant PSA elevation warrants further evaluation.
How to Stay Safe on TRT
The single most important safety measure is regular monitoring. A responsible treatment protocol includes blood work at 6–8 weeks after starting (to check testosterone levels, hematocrit, and metabolic markers), follow-up labs every 3–6 months, annual comprehensive panels including PSA, lipids, and metabolic markers, and ongoing symptom assessment and dose adjustment. This is where quality telehealth platforms shine — they build monitoring into the treatment protocol and make follow-up labs convenient. If a provider prescribes TRT without regular monitoring, that's a red flag. Understanding your symptoms and baseline levels is the foundation, and lifestyle optimization should always complement medical treatment.
TRT is a powerful tool when used appropriately. The key is informed consent, proper dosing, and consistent monitoring — not avoiding treatment out of fear, and not pursuing it without understanding the trade-offs.
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