Testosterone use has gone mainstream.

Podcasters such as Joe Rogan and Andrew Huberman tout testosterone replacement therapy, or TRT, for energy, strength, focus and more.

Starting in July, U.S. military officials started testing active-duty and reserve members for testosterone — the male sex hormone — during their annual checkups. It’s not just middle-aged men who are taking testosterone. Some perimenopausal and postmenopausal women are also taking testosterone products meant for men.

But what is testosterone? Who actually needs it? What are its benefits? And what are the risks of taking it?

To learn more, we caught up with Dr. Margaret Wierman, a UCHealth endocrinologist. Wierman, who previously served for two decades as chief of endocrinology at the Denver Veterans Affairs Medical Center, knows testosterone and its effects on men as well as women. She was the senior author of the Endocrine Society’s guidelines for testosterone therapy in women.

Her bottom line for men: If your fasting testosterone levels aren’t low when measured in the morning, twice, and with a sensitive assay, then you should not be taking extra testosterone.

Testosterone is an anabolic steroid and can come with a host of well-known side effects, said Wierman, who is also a professor of medicine at the University of Colorado Anschutz School of Medicine.

What is testosterone?

Testosterone is the main male androgen, or sex hormone. It’s also present in females at much lower levels. Testosterone is an anabolic steroid. Testosterone supplements are the same steroids that are infamous in doping scandals. Some people also use synthetic androgens that act like testosterone.

“Anabolic” comes from the Greek anabole, meaning “a throwing upward.” Metabolically speaking, anabolic metabolism builds complex molecules from simple ones. With anabolic steroids, that building most prominently has to do with muscle. But testosterone is also involved in metabolism, reproductive function, bone health, red blood cell production and brain function.

What are normal testosterone levels in men?

Rules of thumb vary by laboratory, but Wierman said normal adult-male testosterone levels in a sensitive mass spectrometry assay usually range from 300 nanograms per deciliter to 800 ng/dL.

But measuring testosterone isn’t straightforward, Wierman said. In older men in particular, levels can fluctuate as much as 30% over the course of a day, with levels typically highest in the morning and declining from there. Wierman said she and colleagues typically do two fasting testosterone measurements in the morning to establish a baseline.

Men whose testosterone levels are anywhere within the normal range — but maybe not as high as they used to be — shouldn’t take testosterone replacement therapy, Wierman said.

“So many men think, ‘Oh, I used to be an 800, and I’m a 400, so that’s low, so I should go to a low-T clinic and get to a very high level,’” Wierman said. “But normal is normal.”

Is low testosterone a real medical condition?

Low testosterone can be a legitimate health issue for some men, but it’s not as prevalent as TRT advocates might lead you to believe. Male hypogonadism, as testosterone below 300 ng/dL is called, increases with age. It affects fewer than 1% of men under age 30, about 12% of men in their 50s, about 20% of men in their 60s, about 30% of men in their 70s and about half of those in their 80s.

The main driver of that decline over time isn’t the production of testosterone itself, but increasing levels of sex hormone-binding globulin, or SHGB which binds to testosterone in the circulation. The liver produces it, and so, she said, “anything that alters liver metabolism could make your total testosterone look high or low.”

Also, other contributors to lower testosterone measurements can be at play, including obstructive sleep apnea, obesity, exposure to glucocorticoids such as prednisone, opioids, and dietary supplements, she said.

Symptoms of male hypogonadism can include low sex drive, erectile dysfunction, fertility problems, fatigue, weight gain, loss of muscle mass, poor concentration and depressed mood.

Wierman is among many physicians who said that low testosterone levels alone shouldn’t be an automatic trigger for testosterone replacement therapy. Rather, she said, the decision to start testosterone therapy should be based on a combination of clinically measured low testosterone and accompanying symptoms.

What’s called symptomatic low testosterone requires a low testosterone measurement plus at least three symptoms. That combination is much less common: Only about 6% of men across age groups meet it.

Some men with low testosterone have no symptoms; some with normal testosterone have low-T symptoms. Wierman said the combination of carefully measured low testosterone and symptoms is a must for men to benefit without excessive risk.

What are the benefits of testosterone replacement therapy (TRT)?

For men with hypogonadism, boosting testosterone can improve muscle mass, speed recovery after hard workouts, reduce fat mass, boost bone density, boost libido and sexual function, lower type 2 diabetes risk, alleviate fatigue and help with depressive symptoms. Some of these benefits extend to men whose testosterone supplementation boosts their testosterone above normal levels.

“It’s an anabolic steroid. Everybody feels “better” on testosterone. But is it safe? No, it’s not safe to give to men who are normal,” Wierman said. “We want to treat the underlying cause when it’s not hypogonadism, and when it’s hypogonadism, we want to treat to a physiologic level what the body makes — not high levels — because of the risks.”

What are the risks of testosterone therapy?

There are many well-documented health problems that too much testosterone can cause.

• By suppressing the body’s own testosterone production, too much testosterone can reduce male fertility.
• High testosterone levels can cause noncancerous prostate growth called benign prostatic hyperplasia, or BPH, though that research has focused on men who used testosterone replacement therapy to treat hypogonadism.
• Testosterone at extreme levels can fuel aggressiveness and other behaviors also known as “roid rage.”
• Testosterone replacement therapy can contribute to sleep apnea.
• The boost in red blood cell production that excessively high levels of testosterone can trigger can cause the blood to thicken, putting stress on the heart and increasing the risk of blood clots. That said, a 2023 study found that men on physiologic TRT — that is, TRT to push testosterone levels into the normal range — for hypogonadism had no higher risk of heart attacks or strokes.

Is TRT always needed if someone is diagnosed with low testosterone?

There are cases when TRT is the right answer, Wieman said. But often, low testosterone levels are a downstream effect of a different problem.

The body’s mechanisms for controlling testosterone are complex, involving the brain’s hypothalamus, the pituitary gland, the gonads and the liver. That can make diagnosing the actual cause of low testosterone tricky. For example, the real issue could be a pituitary tumor (the pituitary releases luteinizing hormone, which tells the testicles to make testosterone) or fatty liver disease (affecting SHBG levels and, by extension, those of testosterone), Wierman said.

Alternatively, a patient who’s been getting cortisone steroid shots for joint or other pain could temporarily have low testosterone because the body lowers its own androgen production with the introduced steroid. That’s a muted but similar effect experienced by those who use opioids, certain supplements, and anabolic steroids over the long term.

Surprisingly, untreated sleep apnea often is the real problem, Wierman said. Sleep apnea triggers a complex chain of events starting with increased cortisol (a stress hormone) and rolling into higher levels of catecholamines such as adrenaline. Learn more about sleep apnea.

“Cortisol levels go up, you start to put on weight centrally, catecholamine levels go up, and maybe your blood pressure starts to rise,” Wierman said. “There’s decreased nitric oxide in the cavernosal muscles of the penis, so you have erectile dysfunction, and there’s a slight effect of the low oxygen to turn off the control tower in the brain, so testosterone levels drop slightly.”

Tackling sleep apnea can address those problems, and testosterone levels often normalize, she said. And she notes that testosterone therapy can do the exact opposite, because it can make sleep apnea worse.

Is there a safest way to take testosterone replacement therapy?

One sure-fire risky approach to doing TRT is to do so without close medical supervision because the side effects of too-high testosterone levels are real and can be dangerous.

Otherwise, Wierman said, she recommends shorter-term dosing through lotions or gels or low-dose injections that allow for quick adjustment. She described the long-acting injections and pellets under the skin, which can raise testosterone levels for weeks or months above normal ranges, as “scary.”

“They often produce a dose that brings the level two to five times higher than normal,” she said.

Does testosterone replacement therapy boost the odds of getting prostate cancer?

Recent research suggests that testosterone replacement therapy doesn’t in itself increase prostate cancer risk. But TRT can lead to benign prostatic hyperplasia, a swelling of the prostate gland.

Can men with prostate cancer take testosterone therapy?

Prostate cancer cells need testosterone to grow. Testosterone replacement therapy is a no-go for men with prostate cancer. In fact, doctors often prescribe the opposite — androgen deprivation therapy, or ADT — to slow or stop prostate cancer growth. Doctors use androgen deprivation therapy in combination with radiation therapy, surgery or other prostate cancer treatments.

That said, recent research appears to contradict previous conventional wisdom that testosterone supplementation boosts the odds of prostate cancer recurring or progressing.

What are normal testosterone levels in women?

Normal testosterone levels for women range from about 10 ng/dL to 50 ng/dL before menopause and from 5 ng/dL to 20 ng/dL after menopause. Such levels are difficult to measure with standard lab tests, Wierman said.

How can testosterone replacement therapy help postmenopausal women?

“There are no data to suggest that there’s an androgen deficiency syndrome in women, meaning a testosterone level that correlates with signs and symptoms that are reversed when testosterone is given,” Wierman said.

While we need better solutions to help women get through the many challenges of menopause, testosterone is no panacea. At present, there a single proven use for testosterone therapy for postmenopausal women: for something called hypoactive sexual desire disorder, or HSDD. Even then, effects are modest, Wierman said.

“The studies show that, by driving testosterone to high-normal premenopausal ranges — the kind of levels that we see in hairy women who have acne and are infertile —women had better libido and one more episode of satisfying sexual intercourse per month,” Wierman said. There currently are no data to support effects on cognition, bone and muscle health or wellness, she added.

Otherwise, Wierman pointed to risks such as the body’s conversion of high levels of testosterone to estradiol, which may increase breast cancer risk. More generally, she said, there’s just not enough data on the long-term health impacts of testosterone supplements in women after menopause.

“It’s going to rev you up. It’s going to make you have more energy And if you’re depressed, if your husband isn’t responsive, if your kids are driving you crazy, testosterone may help you in the short term — but with potential risks, and that’s where we don’t have enough data,” Wierman said.

Wierman will help shape how that data may be collected and used to the benefit of postmenopausal women: On Sept. 17, 2026, she will be among the scientists speaking at a U.S. Food and Drug Administration meeting aimed at informing future research and potential low-dose testosterone drug development for menopausal women.

“Further research is needed,” she said.