Everything You Need to Know About Testosterone Therapy

Testosterone therapy has exploded in recent years. Celebrities, influencers and politicians now openly admit to using it.

Conservative estimates suggest that prescriptions for testosterone grew from 7.3 million to more than 11 million between 2019 and 2024, according to the health care research company IQVIA (though spotty reporting could mean that number is much higher).

This emergence into the mainstream has been driven by two factors. First, there is a growing understanding among doctors that synthetic testosterone is a safe, effective way to ease symptoms of testosterone deficiency (or “hypogonadism”), which include chronic fatigue, low libido, erectile dysfunction, irritability, weight gain, muscle loss and depression.

But the boom has also been fueled by the rise of questionable clinics often selling the hormone as a cure-all to those who don’t need it. According to the American Urological Association, up to a third of men taking testosterone have never been diagnosed with a deficiency — and therefore may not benefit from the therapy.

“Ironically, most men who need testosterone don’t receive treatment, while those who don’t need it, do,” said Dr. Abraham Morgentaler, a urologist and testosterone therapy specialist. Low testosterone becomes increasingly common as men age. Specific estimates for testosterone deficiency vary, depending how the condition is defined and diagnosed — some as low as 6 percent of men over 30 and others as high as a third of those over 45.

The condition is relatively easy to treat, but experts encourage men to work with legitimate health professionals who follow proper guidelines, as the therapy does come with risks. Here is what you should know before exploring treatment.

What causes low testosterone?

Most men will experience a natural decrease in testosterone as they age. However, this gradual decline is usually not enough to qualify as a deficiency.

“The problem is, as we get older we also happen to get less healthy,” said Dr. Mohit Khera, a urologist and past president of the Sexual Medicine Society of North America. And chronic diseases like obesity, diabetes and high blood pressure hurt our testosterone levels.

Of these, obesity is the biggest driver of low testosterone. Conversely, losing weight often increases levels. But it can be “extremely difficult” for obese men to lose enough weight on their own to resolve symptoms of testosterone deficiency, Dr. Morgentaler said.

Testosterone is mostly produced while we sleep, so chronic sleep disorders like sleep apnea can cause levels to drop, as can chronic stress. Injury or trauma to parts of our body responsible for producing or regulating testosterone — the testicles, the adrenal glands and certain parts of the brain — can also affect levels.

Transgender men also have lower levels than most cisgender men — and often use the hormone as a part of gender-affirming care.

What are the symptoms of testosterone deficiency?

Symptoms of testosterone deficiency occur in three main ways, Dr. Morgentaler said:

• Sexual symptoms: Low testosterone levels can cause dysfunctions like low sex drive or difficulty achieving and maintaining an erection.

• Physiological symptoms: Low testosterone can also cause men to gain fat and lose muscle. Deficient levels can also cause decreased bone density and lower red blood cell count and can leave men at a greater risk of developing heart disease and type 2 diabetes.

• Psychological symptoms: Testosterone helps regulate our moods and energy; low levels can cause feelings of depression, fatigue, lack of motivation and difficulty concentrating.

While most men will experience one or two of these symptoms on occasion, those with truly deficient levels tend to experience many simultaneously — and often more intensely. “Everybody is tired on occasion,” Dr. Morgentaler said, but those with deficiency can experience an extraordinary level of fatigue, where “even a good night’s rest doesn’t help.”

How is testosterone deficiency diagnosed?

Most experts say a diagnosis should rely on both blood tests and clear, persistent symptoms, said Dr. John Mulhall, who chaired the committee that developed American Urology Association’s most recent treatment guidelines. (Food and Drug Administration guidelines are stricter, requiring a condition affecting testosterone-producing parts of the body.)

According to A.U.A. guidelines, healthy testosterone levels in men fall between 300 and 1,000 nanograms per deciliter. However, testosterone can fluctuate widely. Levels are highest in the morning and can be lower depending on sleep quality, stress and alcohol consumption. So most insurance companies require two blood tests, both showing low levels, before covering treatment.

Different men feel healthy at different testosterone levels, meaning that some symptomatic men who fall in the “normal” range may still benefit from treatment. Similarly, most experts agree that men with low levels who exhibit no symptoms should not be treated.

If a patient’s blood tests are low, “but he tells me he’s feeling great, I’m not treating him,” Dr. Khera said.

Also, several other conditions can present symptoms that are “nearly identical” to those of testosterone deficiency, he added, including chronic fatigue, hypothyroidism, sleep apnea and depression.

How is therapy administered?

Testosterone therapy — which uses a synthetic version of the hormone — is most commonly administered through injections, gels, implantable pellets and oral medications.

These are simply different “delivery systems for the same drug,” Dr. Khera said.

Regardless of the mechanism, the aim of therapy is to raise levels just enough to reduce symptoms, typically staying within the range naturally occurring in the body. (The anabolic steroids sometimes abused by athletes are chemically similar but often taken in much larger doses.)

Injections

Injecting testosterone is “cheap and effective, which is why most men go this route,” Dr. Khera said. The shots are usually self administered, weekly or biweekly, in the thigh or buttocks. Most insurers will cover injections for men with a testosterone deficiency diagnosis. Out of pocket, the therapy can cost around $40 a month.

The main drawback is for men with a needle phobia. There can also be issues with skin sensitivity, soreness and inconveniences while traveling.

Gels

Testosterone therapy can also be delivered through gels and creams applied directly to the skin. The most common is Androgel, which is applied to the shoulders, upper arms or abdomen.

Unlike injections, however, gels must be used every day to work effectively and can be messy. Without insurance, they can also cost $200 to $500 a month.

The biggest concern posed by gels is the risk to others. There have been reported cases in which children have undergone puberty prematurely because of contact with family members who used gels. If men “come in contact with prepubescent children or pregnant women on a regular basis, they probably should not be using gels,” Dr. Mulhall said.

Pellets

Testosterone can also be introduced into the body through pellets implanted under the skin — usually near the hip or buttocks — that slowly dissolve over the course of three to six months, releasing a steady amount of the hormone. The main advantage of the pellets is all but eliminating the risk of skipping or forgetting doses.

Oral medications

Testosterone pills have long existed but have rarely been prescribed because of heightened risk of liver toxicity. However, a new class of oral drugs (Jatenzo, Tlando and Kyzatrex) removes that risk and has been found to be effective at treating symptoms. The major benefit is familiarity. “Americans like pills,” Dr. Khera said. The pills need to be taken twice daily, however.

What are the risks of testosterone therapy?

As long as testosterone therapy is correctly administered and monitored, the downsides to the therapy “are not very many” for men with a true deficiency, Dr. Mulhall said. Still, there are several that patients should know.

Fertility

Using synthetic testosterone signals the brain to reduce sperm production in the testicles — which can affect fertility and can cause testicles to shrink. Fertility and testicular size can often be recovered after stopping the therapy, Dr. Mulhall said, “but not always.”

Men on testosterone who want to preserve fertility can take a second hormone, called human chorionic gonadotropin, which prompts the testicles to keep making sperm.

Others can forgo synthetic testosterone and instead take clomiphene citrate (Clomid), which increases the body’s natural production of the hormone — thus preserving fertility and testicular size. This method doesn’t work for men who are unable to produce their own testosterone, and most insurers don’t cover this.

Heart health

Testosterone therapy can cause an increase in red blood cells, which is not a concern “if the concentration remains within normal ranges,” Dr. Mulhall said. Levels above that can create a heightened risk for heart attacks and strokes.

Your doctor can help address this by lowering your dosage, drawing blood periodically or switching you to a different method. (One study found that injecting testosterone carried the most risk.)

Until recently, many experts thought testosterone therapy could directly cause heart conditions. However, the results from a 2023 study, the largest and most comprehensive to date, found that the therapy posed no increased heart attack or stroke risk when compared with a placebo.

Though A.U.A. guidelines still advise practitioners to warn patients about potential heart complications.

Prostate cancer

Though testosterone was first synthesized in the 1930s, there was a near “global prohibition” against its use to treat testosterone deficiency because of fears it caused prostate cancer, said Dr. Morgentaler. This has largely been disproved, thanks partly to his work, and therapy may even help prevent cancer.

Increase in estrogen levels

Estrogen is important to men’s health. However, testosterone therapy can also increase estradiol, a type of estrogen, to levels that, in men, can cause water retention, mood changes and the development of breast tissues. Though not life threatening, these side effects can be unpleasant and disruptive to some men, Dr. Mulhall said.

Effects on the skin

Testosterone replacement therapy can also cause men to sweat more and their skin to become oily and sensitive, which can clog pores and lead to acne on the face, the chest, the back and the shoulders. Problems can be addressed with proper skin hygiene, lowering testosterone dosage or prescription medications.

Should you seek treatment from a testosterone clinic?

As interest in testosterone increased in recent decades, so too has the number of clinics offering the therapy, many of which forgo proper guidelines. Of particular concern to experts is the rise of clinics that are willing to prescribe testosterone to men who don’t have deficient levels.

There is also a “plateau effect” with testosterone, Dr. Khera said, meaning that once you reach your personal threshold, taking more of the hormone “isn’t going to do very much.”

The exception to this is in building muscle and losing fat — which is why the therapy is popular among certain gym goers. Some clinics push men’s testosterone above naturally occurring levels, which “helps with gym performance,” Dr. Mulhall said, but also “increases the risk of complications.”

A surprising number of providers don’t know their patients’ hormone levels at all — a study found that up to 25 percent of testosterone therapy patients had never had a blood test before starting treatment, while 50 percent had never received one after starting.

Regardless of symptoms, Dr. Mulhall recommended all men over 40 get their testosterone levels checked, to have something to compare with later. Wherever you seek care, experts advise to make sure you’re working with a doctor who is interested in treating your symptoms — not just in increasing your testosterone levels.

David Dodge is a freelance writer focusing on health, wellness and LGBTQ issues.