In a large study from several countries, men with the lowest testosterone levels had an 18% higher risk of dying from cancer than men with the highest levels. The researchers say this is a warning sign, not a reason to start treatment. The same study found no proof that testosterone supplements lower cancer risk. That goes against what many online influencers have been pushing.
The study was published in The Lancet Healthy Longevity in June 2026. It looked at long-term data on more than 26,000 men from 11 studies in Australia, the United States, and Europe. Researchers compared hormone levels in blood taken earlier in the men’s lives with cancer cases and deaths over the following decades. It is one of the largest studies ever done on male hormones and cancer risk.
Testosterone has become an obsession for many online influencers, podcasters, and self-styled health coaches. They paint it as the core of a man’s energy, strength, and even who he is. Some of this content comes from online groups that treat testosterone as a measure of manhood. They push supplements or shots as a quick fix. This study did not look at those groups. It does not find that following their advice causes cancer. It finds a link between low testosterone and later cancer death. And it found no proof that taking testosterone would lower that risk.
Low testosterone does seem to matter for long-term health, including cancer death. But the fix often pushed on social media, hormone shots taken without a doctor, is not backed by this research. It can also carry real risks.
What did the study find about testosterone and cancer?
Men whose testosterone was in the lowest fifth had an 18% higher risk of later dying from cancer than men in the highest fifth. The Lancet Healthy Longevity study found that cancer mortality risk started to rise when testosterone fell below 8.6 nanomoles per liter. That’s about 248 nanograms per deciliter. In young, healthy men, the normal range is usually 10 to 30 nanomoles per liter. Older men tend to have lower levels.
Men with very low testosterone at the start were also more likely to be diagnosed with cancer at all. That risk rose when levels fell below 7.3 nmol/L. The researchers also looked at dihydrotestosterone, or DHT. DHT is a strong hormone the body makes from testosterone. Lower DHT levels were also linked to more cancer deaths.
The link was not the same for every type of cancer. Doctors treat prostate cancer by lowering testosterone. So people have long wondered if a man’s natural testosterone level affects his prostate cancer risk. The study found that prostate cancer risk was more closely tied to low levels of two other hormones, SHBG and luteinizing hormone, than to testosterone itself.
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SHBG stands for sex hormone-binding globulin. It’s a protein that controls how much testosterone and other sex hormones are free to work in the blood. Luteinizing hormone is the signal the brain sends to the testes to make testosterone. Both are part of the same hormone system. Each seems to tell doctors something separate about cancer risk.
A Warning Signal, Not a Diagnosis
The study only found a link. It can’t prove that low testosterone causes cancer. It also found no proof that testosterone treatment would lower cancer risk. Instead, low testosterone may be an important “biomarker,” a sign in the blood that could help spot men who may do worse if they get cancer. Professor Yeap said low testosterone should be seen as a possible warning sign and a reason to get a full checkup.
A biomarker is a sign, not a cause. When a blood test shows surprisingly low testosterone, it may point to something else going on in the body. That something could both lower hormones and help cancer grow or spread faster. Low testosterone could lead doctors to look deeper and find other health problems or risk factors.
The research team was clear on one point. Professor Bu Yeap of the University of Western Australia led the study. He said: “while we’ve shown low levels are associated with increased risk, we haven’t got any evidence yet that actually giving men testosterone will reduce that risk.” He added that men found to have low testosterone should “go to the doctor for a full checkup.” A checkup may find a health problem that no hormone shot will fix.
If you’re wondering about your own levels, start with a blood test ordered by a doctor, not a kit bought online. Normal ups and downs in energy, sex drive, or mood don’t mean you have low testosterone. Doctors don’t recommend testing every man. Many healthy men have lower levels with no symptoms, and testosterone therapy has serious health risks.
Why Testosterone Levels Have Been Falling for Decades
Scientists agree that testosterone levels have dropped over generations. Several studies have found that average levels in men have fallen in recent decades. The drop seems bigger than what normal aging would explain.
Obesity is a major cause. Body fat can turn more testosterone into estrogen. Obesity can also cause insulin resistance and inflammation, which get in the way of the system that makes testosterone.
Obesity is not the only cause. Less exercise, poor sleep, high-calorie diets, and conditions like diabetes all lower testosterone. Research has also linked certain chemicals called phthalates to changes in testosterone. Phthalates are found in plastics and personal care products.
Most of these causes are things people can change. So the drop is not certain for every man. Research suggests that losing extra weight, sleeping better, and moving more can help raise testosterone in men whose low levels come from these habits, without a prescription.
What is the problem with unsupervised testosterone therapy?
Some online groups are right that testosterone is an important health marker. But they have built a whole culture around pushing levels as high as possible, whether or not a man actually has low testosterone. A study in Social Science & Medicine looked at 46 popular Instagram and TikTok posts selling testosterone tests and treatments. The accounts reached nearly seven million followers and got more than 650,000 likes. Not one post cited scientific evidence.
“Influencer marketing is reframing everyday experiences like fatigue, stress, lower libido or ageing as signs of testosterone ‘deficiency’ that requires medical intervention,” said Dr. Brooke Nickel. She is the senior author of that study and a senior research fellow at the University of Sydney’s School of Public Health.
Evidence shows some people are taking testosterone replacement therapy even when their levels are normal. Taking testosterone can make the body stop making its own. It shuts down the system in the brain and testes that controls testosterone and sperm. The body can then come to depend on the added hormone.
The risks of testosterone replacement therapy (TRT) without a doctor are real. The Cleveland Clinic says TRT can lower sperm count and cause fertility problems. It is unsafe for men with certain conditions, including prostate cancer and heart failure. As influencers make testosterone therapy seem normal for healthy young men, it has been linked to serious risks. These include heart problems, infertility, kidney problems, blood clots, lower sex drive, and erection problems.
Dr. Nickel warned that selling tests and treatment to men who don’t need them can lead to men being diagnosed and treated when they shouldn’t be. Men who follow online advice and give themselves testosterone may be shutting down the very hormone production that matters for long-term health. At the same time, they take on risks that have nothing to do with their real hormone levels.
What does this mean for you?
This research does not mean every man should rush to get his testosterone checked. It also doesn’t mean he should start injecting hormones bought outside the medical system. If a doctor’s blood test shows surprisingly low testosterone, that is worth looking into. It may point to obesity, metabolic problems like diabetes, poor sleep, or other conditions that can be fixed. If left alone, these can affect far more than energy and sex drive.
If you want to support healthy testosterone without drugs, the research keeps pointing to the same habits. Keep a healthy weight, exercise regularly, get enough sleep, and cut back on hormone-disrupting chemicals in plastics and personal care products. These same habits help your metabolism and heart. This study can’t show that they would lower the risk of dying from cancer. But they are a sensible place to start while you talk with your doctor.
Some men do have confirmed low testosterone, diagnosed by a doctor through repeat blood tests and ongoing symptoms. They have real treatment options through proper medical care. TRT can help men who truly have low levels when a doctor supervises it. But no current research supports using testosterone to prevent cancer, to boost men with normal levels, or as something to take on your own because a podcast said so.
Disclaimer: This information is not intended to be a substitute for professional medical advice, diagnosis, or treatment and is for information only. Always seek the advice of your physician or another qualified health provider with any questions about your medical condition and/or current medication. Do not disregard professional medical advice or delay seeking advice or treatment because of something you have read here.
AI Disclaimer: This article was created with the assistance of AI tools and reviewed by a human editor.