Testosterone levels naturally decline as men age, but other factors can contribute to low levels. Genetics, chemotherapy, radiation, and injuries to the testicles can all affect testosterone production. Lifestyle factors, like excess body weight and lack of sleep, also play a role.
Age
Testosterone peaks in early adulthood and gradually declines with age. By age 65 to 70, around 10 to 15 percent of men may have levels below 250 ng/dL, while normal levels typically range from 300 to 1,000 ng/dL. “There is a natural decline in the testicles’ ability to make testosterone as men get older,” says Bradley Anawalt, chief of medicine at the University of Washington Medical Center.
Body Weight
Excess body fat reduces the protein that carries testosterone in the blood and blunts the brain-to-testicle signals that produce the hormone. In studies of men with obesity, nearly 43 percent had testosterone under 300 ng/dL. Losing 10 percent of body weight can increase testosterone levels by about 80 ng/dL.
Other Factors
Medications like opioids, poor sleep, and chronic health conditions such as type 2 diabetes or high blood pressure can also lower testosterone. “Low testosterone does not always mean therapy is necessary. Lifestyle changes like exercise and weight loss can improve both health and testosterone,” notes Michael Irwig, endocrinologist at Harvard Medical School.
Potential Benefits of Testosterone Therapy
Several large trials have explored testosterone replacement therapy (TRT) in men with low testosterone and related symptoms. The benefits vary depending on age, baseline testosterone levels, and overall health.
Sexual Function
TRT can improve sex drive and erectile function, though typically less effectively than medications like Viagra. These effects are most pronounced in men with clinically low testosterone.
Mood and Energy
Studies show modest improvements in mood and vitality in men with low testosterone, but men with testosterone levels at the lower end of normal often see little difference. Cognitive function does not appear to improve with TRT.
Physical Strength and Endurance
TRT may modestly enhance physical performance in older men who are not frail. For example, some participants in the Testosterone Trials improved their six-minute walk distance by approximately 164 feet compared to 13 percent in the placebo group. Effects are generally modest and designed to restore normal testosterone levels rather than dramatically increase strength.
Risks of Testosterone Therapy
Fertility
TRT can reduce sperm production by signaling the testicles to stop making testosterone locally, potentially causing infertility. Recovery can take 6 months to 2 years after discontinuation.
Red Blood Cell Count
Testosterone can increase red blood cells, raising the risk of blood clots. Regular monitoring and dosage adjustments can reduce this risk.
Cardiovascular Health
Large studies have found no significant increase in heart attacks, strokes, or cardiovascular deaths with moderate-dose TRT in men with low testosterone. Rare complications such as irregular heart rhythms or kidney issues have been observed.
Prostate Concerns
Current evidence does not indicate that TRT increases prostate cancer risk, though PSA levels may rise, leading to more prostate biopsies. Long-term effects remain uncertain.
Diagnosing Testosterone Deficiency
A diagnosis of low testosterone, or hypogonadism, requires both consistently low blood levels and related symptoms, such as reduced libido, fatigue, or erectile dysfunction. Morning testosterone measurements on multiple days are necessary for accuracy. Screening all men is not recommended.
Supplements and “Natural” Testosterone Boosters
Despite claims, dietary supplements containing ingredients like ashwagandha, fenugreek, or Tribulus terrestris have little reliable evidence for raising testosterone. Studies are often flawed, and any observed increases are usually minor and temporary.
The Rise of Direct-to-Consumer Testosterone Services
Online platforms and men’s health clinics offer TRT without traditional doctor visits. While convenient, many fail to provide full guidance on risks, particularly fertility. Experts advise men to carefully evaluate providers, consider costs, and seek a second opinion when necessary.
Bottom Line
Testosterone therapy can be beneficial for men with low levels and symptoms of deficiency, but it is not a cure-all for aging, fatigue, or weight issues. Lifestyle changes—such as exercise, proper sleep, and maintaining a healthy weight—remain essential. Supplements claiming to boost testosterone generally lack scientific support, and direct-to-consumer services may not provide comprehensive care.
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