Hormone replacement therapy for men, commonly called testosterone replacement therapy (TRT), is a medical treatment that restores testosterone to normal levels in men whose bodies no longer produce enough on their own. A diagnosis typically requires a morning blood test showing total testosterone below 300 ng/dL along with specific symptoms like reduced sex drive, erectile difficulties, or persistent fatigue. TRT is one of the most common hormonal treatments prescribed to men, and understanding how it works, what it involves, and what risks come with it can help you make an informed decision.
Why Testosterone Drops and Who Qualifies
Testosterone production naturally declines with age, dropping roughly 1% to 2% per year after age 30. But age isn’t the only factor. Injury to the testes, pituitary gland disorders, obesity, chronic illness, and certain medications can all drive levels down faster or earlier than expected. The clinical term for this is hypogonadism, and it affects a significant number of men over 40.
Getting diagnosed isn’t as simple as having a low number on a blood test. Guidelines from the American Urological Association require both a testosterone level below 300 ng/dL and the presence of symptoms. Blood draws should happen between 7 and 11 AM, when testosterone peaks. Sexual symptoms carry the most diagnostic weight: fewer morning erections, erectile dysfunction, and reduced sexual thoughts. Other common signs include unexplained fatigue, depressed mood, difficulty concentrating, and loss of muscle mass. If your levels are borderline, your doctor will typically repeat the test on a separate morning before making a diagnosis.
How TRT Is Administered
There’s no single way to take testosterone. The right method depends on your lifestyle, comfort with needles, and how your body responds. Each delivery method reaches the same goal of raising your blood testosterone into the normal range, but they differ in convenience, cost, and how steady your levels stay throughout the week.
- Injections are the most widely used option. Testosterone cypionate is typically injected into muscle at doses of 75 to 100 mg weekly or 150 to 200 mg every two weeks. Some men prefer weekly shots because they produce more stable blood levels with fewer mood and energy swings between doses.
- Topical gels are applied once daily in the morning, usually to the shoulders, upper arms, or thighs. Starting doses are generally 40 to 50 mg per day, adjusted based on follow-up blood work. The main drawback is the risk of transferring testosterone to a partner or child through skin contact before the gel dries completely.
- Subcutaneous pellets are small implants placed under the skin in a fatty area, typically near the hip. They release testosterone slowly over three to six months, which appeals to men who don’t want to think about daily or weekly dosing. A minor in-office procedure is needed each time they’re replaced.
Your doctor will check your testosterone levels after starting treatment and adjust the dose to keep you within the normal range, generally aiming for levels between 450 and 600 ng/dL, though individual targets vary.
What to Expect and When
TRT doesn’t produce overnight results. Different symptoms improve on different timelines, and knowing what to expect can prevent frustration in the early weeks.
Sexual interest is often the first thing to improve. Most men notice changes in libido within three weeks, with effects leveling off around six weeks. Improvements in erectile function and overall sexual satisfaction may take three to six months to fully develop, and in some cases up to a year.
Mood changes follow a slightly longer arc. Depressive symptoms can begin lifting within three to six weeks, but the most meaningful improvement typically takes 18 to 30 weeks. Men with severe depression may respond more slowly, since testosterone interacts with other brain chemistry that may also need attention.
Body composition changes take the longest. You can expect to see shifts in fat and lean muscle mass starting around 12 to 16 weeks, with results stabilizing between 6 and 12 months. Muscle strength improvements follow a similar pattern, becoming measurable after 12 to 20 weeks and reaching their peak around the 6- to 12-month mark. These gains can continue marginally over years of continued treatment.
Benefits Beyond Symptom Relief
The most noticeable benefits of TRT are the ones that brought you to the doctor in the first place: better energy, improved sexual function, and a more stable mood. But testosterone also has measurable effects on bone health that matter as men age.
In a controlled clinical trial of older men with low testosterone, one year of treatment increased spine bone density by 7.5%, compared to less than 1% in men receiving a placebo. Estimated bone strength in the spine improved by nearly 11%. Hip bone density also increased, though more modestly, at about 1.2%. These changes are meaningful because low testosterone is an underrecognized contributor to osteoporosis in men, and fractures become a serious health risk later in life.
Cardiovascular Safety
For years, one of the biggest concerns about TRT was whether it increased the risk of heart attack or stroke. The TRAVERSE trial, published in the New England Journal of Medicine, was specifically designed to answer this question. It followed men with low testosterone who also had preexisting heart disease or significant cardiovascular risk factors.
The results were reassuring. Major cardiovascular events, including heart attack, stroke, and cardiovascular death, occurred at nearly identical rates in men taking testosterone (7.0%) and men taking a placebo (7.3%). The study concluded that TRT was noninferior to placebo for cardiovascular safety, meaning it did not increase risk in this population. A 2025 meta-analysis of 41 randomized controlled trials reached a similar conclusion, finding no statistically significant increase in major cardiac events.
Prostate Cancer Concerns
The relationship between testosterone and prostate cancer has been debated for decades. Because prostate cancer cells can be sensitive to androgens, there was a longstanding worry that raising testosterone levels could fuel tumor growth. Current evidence doesn’t support that fear for men without existing prostate cancer. The same meta-analysis of 41 trials found no significant increase in prostate cancer events among men receiving testosterone therapy, with short- to mid-term data showing similar rates between treatment and placebo groups. Your doctor will still monitor your PSA levels during treatment as a routine precaution.
Side Effects and Monitoring
TRT is generally well tolerated, but it does come with side effects that need regular monitoring. The most clinically important one is a rise in hematocrit, the percentage of your blood made up of red blood cells. Testosterone stimulates red blood cell production, and hematocrit increases by roughly 4% regardless of the formulation used. If it climbs above 52%, your doctor may recommend a therapeutic blood donation (phlebotomy) to bring it back down, since thickened blood raises the risk of clotting.
Acne is another common side effect, driven by testosterone’s effect on oil glands in the skin. It tends to be mild and manageable for most men. Some men also develop gynecomastia, a tenderness or swelling of breast tissue, which happens when excess testosterone converts to estrogen. This is more likely when estrogen levels rise above a certain threshold and can usually be addressed with a dose adjustment.
Routine blood work every 6 to 12 months is a standard part of TRT. Your doctor will track your testosterone and hematocrit levels, along with PSA and sometimes estrogen.
The Impact on Fertility
This is one of the most important and least understood consequences of TRT. Testosterone replacement therapy suppresses your body’s natural signal to produce sperm. In studies, 65% of men with normal sperm counts became azoospermic (producing zero sperm) within four months of starting treatment. At six months, that rate reached 64% to 75% depending on the formulation.
If you’re planning to have children, TRT is not the right treatment. It functions, in effect, as a male contraceptive. Sperm production can recover after stopping treatment, but recovery isn’t guaranteed. In one study, 30% of men were unable to achieve adequate sperm counts even after 12 months of recovery therapy using medications designed to restart production. If you have low testosterone and want to preserve fertility, alternatives exist that stimulate your body’s own testosterone production without shutting down sperm. These are conversations to have with your doctor before starting any treatment.
What Long-Term Treatment Looks Like
TRT is typically a lifelong commitment. Once you begin, your body’s own testosterone production decreases further because the external supply signals the brain to stop stimulating the testes. Stopping treatment abruptly can cause a temporary crash in testosterone levels, often worse than where you started, until natural production gradually resumes.
Most men on TRT settle into a routine: a weekly injection, a daily gel application, or a pellet insertion every few months, paired with periodic blood work. The treatment becomes part of the background of daily life, much like managing any other chronic condition. When levels are dialed in and side effects are managed, the majority of men report sustained improvements in energy, mood, sexual function, and overall quality of life.