Testosterone replacement therapy is not inherently bad for you when prescribed for a legitimate deficiency and monitored properly. The largest safety trial to date, called TRAVERSE, followed over 5,000 men for an average of 22 months and found that TRT was no worse than placebo for major heart events like heart attacks and strokes. That said, TRT carries real risks that depend on your health profile, your dose, and how closely you and your doctor track certain blood markers.
Heart Risk Is Lower Than Previously Feared
For years, the biggest concern about TRT was cardiovascular safety. Earlier observational studies sent mixed signals, and the FDA added a warning label in 2015. The TRAVERSE trial, published in 2023, was specifically designed to answer this question in men who already had cardiovascular risk factors or existing heart disease. The result: testosterone did not increase the rate of heart attacks, strokes, or cardiovascular death compared to placebo. This doesn’t mean TRT is protective for your heart, but it does mean the worst-case scenario many men worried about hasn’t materialized in rigorous testing.
The Blood Thickening Problem
The most common medical side effect of TRT is polycythemia, a condition where your body produces too many red blood cells. This thickens your blood and raises the risk of clots, which can lead to stroke or pulmonary embolism. The key number to watch is your hematocrit level, which measures the percentage of your blood volume occupied by red cells.
The American Urological Association recommends reducing your dose or pausing therapy if hematocrit reaches 54%. Some clinicians intervene earlier, recommending blood donation (therapeutic phlebotomy) when levels climb above 50% or 52%. This is why regular blood work isn’t optional on TRT. Most guidelines call for hematocrit checks within the first few months, then every 6 to 12 months as long as you’re on therapy.
Fertility Can Shut Down
This is the risk that catches many younger men off guard. When you take external testosterone, your brain detects the higher levels and stops signaling your testes to produce their own. Sperm production depends on those signals, so it can drop dramatically or stop entirely. Some men become fully azoospermic, meaning zero sperm in their ejaculate.
The good news is that this is usually reversible after stopping TRT, but recovery is slow. With medical therapy to jumpstart natural production, sperm counts typically begin recovering within four to five months, though full recovery can take up to two years. If you’re planning to have children, this is a conversation to have before starting treatment, not after. Doctors often prescribe alternatives like clomiphene to raise testosterone while preserving fertility.
Sleep Apnea Can Get Worse
If you already have obstructive sleep apnea, or you’re at risk for it due to weight or neck size, TRT can make it worse. Testosterone appears to affect the muscles that keep your airway open during sleep and may alter how your brain responds to drops in oxygen. One large study found that men on TRT had a two-year sleep apnea risk of 16.5%, compared to 12.7% in men not on therapy.
Short-term, high-dose testosterone has been shown to shorten total sleep time and worsen overnight oxygen drops. In one study, oxygen disruption events increased by about 10 per hour at seven weeks, though this effect leveled off by 18 weeks. If you snore heavily or wake up feeling unrested, getting a sleep study before starting TRT is worth considering.
Mood Effects at Normal Doses Are Minimal
The “roid rage” stereotype comes from bodybuilding doses, not therapeutic ones. In a controlled study where men received doses roughly six times higher than a standard TRT prescription (600 mg per week versus the typical 100 to 200 mg), 84% still showed minimal psychiatric effects. About 12% became mildly hypomanic, meaning somewhat elevated mood and energy, and only 4% had more pronounced mood changes. Broader research suggests that significant psychiatric symptoms are rare at 300 mg per week or less, which comfortably covers the therapeutic range.
For men who genuinely have low testosterone, TRT often improves mood, energy, and motivation rather than destabilizing it. The risk of mood disturbance rises sharply when people use testosterone at supraphysiological doses without medical supervision.
Prostate Cancer Fears Are Largely Outdated
The idea that testosterone feeds prostate cancer dates back to the 1940s and has been one of the most persistent concerns around TRT. Current evidence does not support a link between testosterone therapy and new development of prostate cancer. Studies of older men with low testosterone who were treated with TRT have not shown higher rates of prostate cancer compared to untreated men.
What can happen is that TRT raises your PSA level, a marker used to screen for prostate cancer. Higher PSA leads to more biopsies, and more biopsies detect cancers that might have gone unnoticed otherwise, many of which are slow-growing and may never cause harm. This creates the appearance of increased risk when the real change is increased detection. That said, guidelines still recommend PSA testing before starting therapy if you’re over 40, with follow-up if PSA jumps more than 1.4 points above your baseline or exceeds 4.0.
Liver Damage Depends on the Formulation
Older oral testosterone pills (methyltestosterone) were genuinely toxic to the liver, causing abnormal liver function, bile flow problems, and jaundice. Current guidelines explicitly say clinicians should not prescribe these alkylated oral forms. The newer oral formulation, testosterone undecanoate, has been studied over two years with no evidence of liver toxicity and a safety profile similar to injections and topical gels.
If you’re using injectable, topical, or modern oral testosterone, liver damage is not a meaningful concern, and routine liver enzyme monitoring isn’t even recommended for these formulations. This is one area where the reputation of TRT is worse than the reality, as long as the right product is being used.
Bone Density Improves, but Fractures Are Unclear
One of the clearer benefits of TRT for men with low testosterone is improved bone density. In the Testosterone Trials bone study, men on TRT saw a 7.5% increase in spinal bone density compared to just 0.8% in the placebo group. For men with osteoporosis or thinning bones from long-term low testosterone, this is a meaningful improvement.
Surprisingly, though, the TRAVERSE fracture substudy found that men on TRT actually had a slightly higher fracture rate (3.5%) than men on placebo (2.46%). The reason for this is still being debated, and it’s possible that men on TRT were simply more physically active and therefore more exposed to falls and injuries. The bottom line: TRT strengthens bone tissue but hasn’t yet been proven to reduce fractures.
What Monitoring Looks Like
Safe TRT requires blood work on a schedule. In the first year, you’ll typically have testosterone levels checked two to four weeks after starting (for gels, patches, or nasal formulations), then a symptom review at three months to adjust dosing. After that, testosterone and hematocrit should be measured every 6 to 12 months for as long as you stay on therapy. PSA monitoring follows standard prostate screening guidelines, with closer attention to any sudden increases.
The men who run into trouble on TRT are generally those who skip monitoring, use doses higher than prescribed, or obtain testosterone without medical oversight. With proper lab work and dosing, most side effects are caught early and managed with simple adjustments like lowering the dose, switching delivery methods, or scheduling periodic blood draws to keep hematocrit in range.