TRT Side Effects and Risks

FDA-approved testosterone products carry labels, and the effects below come from the warnings on those labels — not from clinic marketing pages.

Blood pressure: FDA says ambulatory blood pressure studies confirmed that testosterone raises blood pressure across the class of products.

The label tells prescribers to monitor blood pressure periodically, and testosterone products are not recommended for patients with uncontrolled hypertension.

Red blood cells: the labels call for periodic hemoglobin and hematocrit checks during long-term therapy to detect polycythemia, a rise in the red-cell side of a blood count.

Blood clots: the label notes postmarketing reports of venous blood clots, including deep vein thrombosis (DVT) and pulmonary embolism.

Prostate: in older men, the label raises the possibility of prostatic enlargement and says men with benign prostatic hyperplasia (BPH) may develop acute urinary obstruction.

That question gets its own section below.

Sperm production is a separate warning, with its own section below as well.

One honest limit: the sources read for this guide do not give incidence rates for these effects in everyday care, and we found no confirmed figures for other effects some sources attribute to TRT, such as acne.

If a clinic quotes you a rate, ask where it comes from.

Fertility is the warning the label explains most mechanically.

Per the Depo-Testosterone label, exogenous androgens — testosterone from outside the body — inhibit pituitary luteinizing hormone (LH) and, at large doses, follicle-stimulating hormone (FSH), the pituitary signals involved in sperm production.

The result, in the label's words, is that spermatogenesis may be suppressed, and oligospermia — a low sperm count — may occur with prolonged use or excessive dosage.

Both "may"s are the label's own, and that is as far as the sources read for this guide go: they describe the mechanism and the possibility, and they do not give a figure for how often sperm counts return to baseline after therapy stops.

If fathering a child is on your timeline, that is a question to put to the prescriber before starting therapy.

Prostate first.

Depo-Testosterone is contraindicated in men with known or suspected prostate cancer.

The same label says geriatric patients treated with androgens may be at an increased risk of prostatic enlargement and prostate cancer, "although conclusive evidence to support this concept is lacking," and it warns that men with benign prostatic hyperplasia (BPH) may develop acute urinary obstruction.

The heart evidence is the TRAVERSE trial (Lincoff et al., NEJM 2023), which enrolled 5,246 men aged 45 to 80 who had hypogonadism and either established cardiovascular disease or a high risk of it.

Participants used a testosterone gel or a placebo.

For major adverse cardiac events, testosterone gel was noninferior to placebo: 7.0% versus 7.3% (hazard ratio 0.96).

Atrial fibrillation, acute kidney injury and pulmonary embolism were more frequent with testosterone.

On February 28, 2025, FDA announced class-wide label changes: TRAVERSE results were added, the boxed-warning language about increased cardiovascular risk was removed, the limitation of use for age-related hypogonadism was kept, and blood-pressure warnings were added or strengthened.

What did not change: the labels still state testosterone is approved solely for men who lack or have low testosterone in conjunction with an associated medical condition, with safety and efficacy for age-related hypogonadism not established.

We did not confirm which products keep other boxed warnings, so ask the prescriber what the label for your product carries.

Read together, the honest summary is narrow: one large trial found testosterone noninferior for major cardiac events in its population while logging more atrial fibrillation, kidney injury and pulmonary embolism, and the labels treat prostate risk as unproven but worth caution.

Lab work bookends labeled TRT.

Before the first dose, the label says to confirm hypogonadism: serum testosterone measured in the morning on at least two separate days, with both results below the normal range.

During long-term therapy, the labels call for periodic hemoglobin and hematocrit checks to detect polycythemia, along with periodic blood-pressure monitoring; testosterone products are not recommended for patients with uncontrolled hypertension.

Notice the labels' word: "periodically." Neither the labels nor the sources read for this guide supply a calendar — no retest-interval figure exists in what we reviewed — so how often to redraw labs is a plan to set with the prescribing provider and get in writing.

One more gap, named plainly: we did not confirm a prostate-specific lab schedule for this guide, so that question goes to the provider too, along with anything in your own history that changes the risk math.

"Monitored" now has a concrete meaning from the sections above: diagnosis labs before the first dose, then periodic blood counts and blood-pressure checks.

Any program — men's clinic, med spa or telehealth — should be able to describe its version of that plan without prompting.

The prescription itself has a federal frame worth knowing before you book: testosterone is a Schedule III controlled substance, listed as an anabolic steroid in 21 CFR 1308.13(f).

Under the Ryan Haight Act, a practitioner normally may prescribe a controlled substance by telemedicine only after at least one in-person medical evaluation.

DEA and HHS's fourth temporary extension keeps the COVID-era flexibilities — no in-person visit required — in effect from January 1, 2026 through December 31, 2026, so the current rules carry an end date worth checking before you enroll.

For what TRT is, the approved forms and who can prescribe it, start with our TRT guide.

For vetting a specific provider's credentials and red flags, our page on how to choose a med spa covers the questions to ask.