There is no specific age when men should start taking testosterone. Testosterone therapy is appropriate only when a man has both consistently low blood levels (below 300 ng/dL on two separate morning tests) and symptoms that match, like low sex drive, fatigue, or loss of muscle mass. Some men never need it. Others develop a deficiency in their 30s due to obesity, diabetes, or other medical conditions.
The idea that testosterone therapy is simply an age-related milestone is one of the most common misunderstandings about the treatment. Here’s what actually determines whether and when it makes sense.
How Testosterone Changes With Age
Testosterone levels peak in early adulthood, typically during the late teens and twenties. After age 30, the average man loses about 1% of his total testosterone per year. That gradual decline is normal and, for most men, never drops low enough to cause problems or require treatment.
The decline means that by 50 or 60, some men will naturally fall below the 300 ng/dL threshold that medical guidelines use as a diagnostic cut-off. But a low number alone doesn’t qualify someone for therapy. The American Urological Association and the Endocrine Society both require a combination of low levels and real symptoms before a diagnosis of testosterone deficiency is made.
Symptoms That Prompt Testing
The symptoms of low testosterone overlap with many other conditions, which is partly why diagnosis requires lab confirmation. Common signs include reduced sex drive, difficulty getting or maintaining erections, persistent fatigue, depressed mood, decreased motivation, trouble concentrating, and loss of muscle mass or increased body fat. Sleep disturbances and irritability are also frequently reported.
None of these symptoms on their own confirm a testosterone problem. Depression, poor sleep, thyroid disorders, and stress can all produce the same picture. That’s why guidelines emphasize that treatment should only start after blood work confirms consistently low levels alongside these complaints.
How the Diagnosis Works
If you suspect low testosterone, the process starts with a blood test measuring total testosterone. The timing matters: testosterone levels fluctuate throughout the day and are highest in the morning. Blood should be drawn before 10:00 AM, or within three hours of waking, ideally while fasting. Testing during jet lag or a shift-work transition can produce misleading results.
Because natural day-to-day variation in testosterone can reach up to 30%, a single low reading isn’t enough. Guidelines require at least two low results on separate days, both drawn in the early morning. A total testosterone level below 300 ng/dL on both tests, combined with symptoms, supports a diagnosis.
Before prescribing treatment, your doctor will also check your hematocrit (the proportion of red blood cells in your blood) and, for men over 40, PSA levels to screen for prostate concerns. Treatment should not be started if hematocrit is above 48 to 50%, if PSA is above 4 ng/mL (or above 3 ng/mL for men at higher risk of prostate cancer), or if you have untreated severe sleep apnea.
Low Testosterone in Younger Men
While age-related decline gets the most attention, younger men can also develop testosterone deficiency. Obesity is one of the most common causes in men under 40. Excess body fat increases the conversion of testosterone to estrogen, suppressing the hormonal signals that drive testosterone production. Poorly controlled type 2 diabetes compounds this effect.
Chronic opioid use is another significant cause, disrupting the brain’s hormonal signaling and creating a secondary deficiency. Anabolic steroid use, whether current or past, suppresses the body’s own testosterone production, often shrinking the testes and reducing sperm count in the process. Even long-term use of common painkillers like ibuprofen and acetaminophen has been shown to alter testicular function.
For younger men with these reversible causes, guidelines recommend addressing the underlying issue first: losing weight, improving blood sugar control, or stopping the offending drug. Testosterone therapy is generally a second step if levels remain low after those changes.
Fertility Is a Major Consideration
This is one of the most important factors in deciding when to start testosterone, and it catches many men off guard. Testosterone therapy suppresses sperm production. Studies show that most men on treatment reach near-zero sperm counts within about three and a half months. If you’re planning to have children, or even think you might want to in the future, this needs to be part of the conversation before you begin.
Sperm production can recover after stopping testosterone. One study found men who were treated with fertility-restoring medications after stopping therapy recovered to an average of 22 million sperm per milliliter within about four months. But recovery isn’t guaranteed for everyone, and the timeline varies.
For men who need treatment for low testosterone but want to preserve fertility, alternatives exist. Certain medications stimulate the body to produce its own testosterone rather than replacing it from the outside, which maintains sperm production. Your doctor can discuss whether these are appropriate for your situation.
What the Heart Safety Data Shows
Concerns about cardiovascular risk kept many men and their doctors cautious about testosterone therapy for years. The TRAVERSE trial, published in the New England Journal of Medicine, was the largest study designed to answer this question directly. It followed over 5,000 men with low testosterone who also had preexisting heart disease or were at high risk for it.
The results showed that testosterone therapy did not increase the rate of major cardiac events like heart attacks and strokes compared to placebo: 7.0% in the testosterone group versus 7.3% in the placebo group. However, the study did observe slightly higher rates of atrial fibrillation, blood clots in the lungs, and acute kidney injury in men taking testosterone. Ongoing monitoring of blood counts and cardiovascular health remains part of standard care during treatment.
What to Expect After Starting
If you and your doctor decide testosterone therapy is appropriate, improvements don’t happen all at once. The timeline follows a predictable pattern based on which symptoms you’re treating.
Libido, sexual desire, and sexual thoughts are among the first to respond, often improving within three weeks. Mood, motivation, and energy levels typically begin improving in the same three-to-six-week window, though the full benefit for depressive symptoms can take 18 to 30 weeks. A decrease in fatigue usually shows up within one to six weeks.
Body composition changes take longer. Shifts in fat and lean muscle mass become measurable at 12 to 16 weeks, stabilize over 6 to 12 months, and can continue improving marginally after that. Erectile function improvements may appear early for some men but can take up to six months to fully develop. Effects on overall quality of life begin within three to four weeks, with maximum benefits building over months.
Once started, testosterone therapy is typically ongoing. Stopping treatment will cause levels to fall back to where they were before, and symptoms will generally return. That’s another reason the decision to start should be deliberate, based on clear diagnostic criteria rather than curiosity about whether it might help.