Testosterone replacement therapy (TRT) can cause side effects, from acne to higher blood pressure, a high red blood cell count, lower sperm count and blood clots. Gels carry an FDA boxed warning because they can pass to children and women by touch. Regular blood tests and blood pressure checks help catch problems early.
The most common side effects in FDA labels and MedlinePlus include:
Tell your clinician about any side effect that bothers you. A change in dose or form may help.
High red blood cell count (polycythemia). Testosterone tells the body to make more red blood cells. Too many can thicken the blood. Hematocrit is checked before and during treatment, and the dose may be lowered or paused if it rises too high.
Higher blood pressure. In 2025, FDA required a blood pressure warning on every testosterone product after blood pressure studies were completed. Higher blood pressure can raise heart and stroke risk over time. Your blood pressure should be checked before you start and regularly after.
Blood clots. Clots in the legs (deep vein thrombosis) and lungs (pulmonary embolism) have been reported. Get care right away for leg pain or swelling, chest pain, or sudden shortness of breath.
Sleep apnea. Testosterone may start or worsen sleep apnea in men with risk factors. Loud snoring or stopping breathing in sleep should be checked.
Swelling (edema). Fluid buildup may happen, especially in men with heart, kidney or liver disease.
Prostate effects. Testosterone may worsen symptoms of an enlarged prostate (BPH). Current labels say not to use it in men with known or suspected prostate cancer. In June 2026, FDA asked makers to update the prostate wording, but labels change only after FDA approves new text.
Misuse. Testosterone is a controlled substance. Taking more than prescribed can harm the heart, liver and mood, and stopping high doses suddenly can cause withdrawal, such as low mood and tiredness.
Yes. Testosterone from outside the body signals the brain to stop telling the testicles to make sperm. Sperm count can drop, sometimes to zero (azoospermia). The American Urological Association advises a fertility review before treatment for men who want children. Other medicines may be used instead, under a specialist's care. Tell Dr. Vargas about family plans at your first visit.
Gel stays on the skin after you apply it. If a child or woman touches that skin, testosterone can pass to them. Children exposed this way have shown early signs of male puberty, and testosterone may harm an unborn baby. To lower the risk, labels advise:
Gels are also flammable until dry, so stay away from fire, flames and smoking until the gel dries.
One long-acting injection (testosterone undecanoate, Aveed) has a different boxed warning: serious breathing problems and allergic reactions can happen during or after the shot. It is given only in a medical office, and you must stay for at least 30 minutes after.
FDA labels and guidelines call for periodic checks of:
How often depends on the product and your health. Dr. Vargas sets a schedule with you and adjusts it over time.
Does TRT cause heart attacks? The large TRAVERSE study found no increase in major heart events with testosterone gel compared with placebo in men with low testosterone and heart risk. Testosterone can still raise blood pressure, which matters for long-term heart health, so it is monitored.
Can TRT cause prostate cancer? Labels say testosterone may increase the risk of prostate problems, and men are checked with PSA before and during treatment. FDA's 2026 review of prostate wording is still being added to labels. Ask your clinician what applies to you.
Can I stop TRT anytime? Talk to your clinician first. Stopping should be planned, because the symptoms of low testosterone may come back. Men who used high doses may also have withdrawal symptoms, such as low mood and tiredness.
Is TRT safe for women? These pages are about men. Testosterone is not FDA-approved for women in the US, and women who are or may become pregnant should avoid contact with it.
Call (210) 903-1030 or Book a visit. In-clinic in San Antonio
Leticia Vargas, MD, OB/GYN, founder of Yaso Wellness Health Clinic. About Dr. Vargas
Education only, not medical advice or a diagnosis. In an emergency, call 911.
