Testosterone (or simply “T”) is a powerhouse. As one of the primary sex hormones, it influences many bodily functions. So, when levels dip below the normal range, consequences can be potent.

Read on to learn the function of testosterone and what to do if your levels fall short.

What is Testosterone?

“Testosterone is a hormone that is important for both men and women,” says Tara Kim, M.D., an endocrinologist at Lenox Hill Hospital in New York City. It’s produced in the testicles (in males) and ovaries and adrenal glands (in females).

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Testosterone gives males their “manly” characteristics (think: facial hair and deep voices) and regulates sex drive and function in both sexes. It also takes part in non-gender-specific processes, like creating red blood cells, keeping bones strong, and boosting mood, according to Harvard Health.

In addition, one review paper published in Endocrine Reviews says that there is a dose-response relationship between circulating testosterone and muscle mass and strength. In other words, the more testosterone you have flowing around your body, the more muscle mass and strength you’re likely to have.

And because testosterone helps create red blood cells (these carry oxygen throughout the body), having higher levels of this hormone may offer endurance benefits. For example, one randomized controlled trial published in 2020 in the British Journal of Sports Medicine found that when a small group of 48 young, active women smeared testosterone cream on their outer thigh every evening for 10 weeks, it helped improve their endurance. The cream boosted their T levels more than four times the initial level and enhanced their endurance performance (measured via a running test on a treadmill) by more than 8 percent.

Those benefits were not without a few adverse events. Side effects included acne in more than half the testosterone group (compared to 25 percent of the placebo group), as well as a few cases of body hair growth and menstrual disturbances.

While it may be pro- to mid-level pro cyclists that would turn to testosterone for its performance-enhancing benefits, if you’re considering taking testosterone supplements, know that it’s essential to avoid these if you plan to participate in any athletic competitions or events. Taking any substance that raises testosterone or mimics the effect of testosterone gives athletes an unfair advantage, which lands T-boosting supplements on the banned list for both the U.S. Anti-Doping Agency (USADA) and World Anti-Doping Agency (WADA). And even if you’re not participating in these events, supplements aren’t the smart choice for addressing T levels.

What are symptoms of low testosterone levels?

We all need a certain amount of testosterone to keep up normal body functions and perhaps even keep our performance on the bike up to par. And some of us—namely, men—need more T than others.

Depending on what source you turn to for information, “normal” ranges of testosterone can vary. In males, a normal range might fall between 300 and 1,000 nanograms per deciliter (ng/dL); anything less than that warrants a “low-T” diagnosis (also known as hypogonadism), according to the 2018 guidelines from the American Urological Association (AUA). In females, testosterone typically sits between 8 and 60 ng/dL, according to Mayo Clinic Laboratories. However, Dr. Kim points out that a low T level for men generally starts at 264 ng/dL, and for women it starts around 15 ng/dL.

According to the Urology Care Foundation, low testosterone symptoms in men can include the following:

  • Lower sex drive
  • Less muscle mass
  • Fatigue
  • Depression
  • Erectile dysfunction
  • Trouble focusing
  • Irritability

In women, Dr. Kim says low testosterone symptoms may present as:

  • Decreased sex drive
  • Thinning, drying, and inflammation of the vaginal walls (also known as vaginal atrophy)
  • Possible mental decline

What causes low testosterone levels?

Testosterone levels can dip below the norm for various reasons—age, for one. According to the Mayo Clinic, testosterone gradually declines in men by 1 percent each year after age 30 or 40. As a result, low testosterone levels are fairly common in older men, affecting as many as 50 percent of men over 80 years old, per the Urology Care Foundation, though again, these numbers can vary and low testosterone can also occur in younger men and women.

“In general, hypogonadism affects 4 million American men,” Dr. Kim says. “But there really is no consistent data on prevalence in older men."

In addition to age, a few other common causes can lead to low testosterone levels, according to Dr. Kim. These include:

  • Chemotherapy or radiation
  • Kidney or liver issues
  • Medications like steroids and opioids
  • Obesity
  • Menstrual cycle irregularities (in women)
  • Trauma to the testicles (in men)

How do you boost testosterone?

Before you think about raising your T levels on your own, see your doctor to make sure you actually have low levels. Your doc may put you through a series of blood tests to check your hormone levels, according to the Urology Care Foundation.

If the results show there’s an issue, your doctor will want to figure out what’s causing your T shortage. This includes checking for underlying conditions and reviewing your medication list to create the best treatment plan for you.

Depending on what your doctor finds, he or she may prescribe medications designed to raise testosterone levels, also known as testosterone replacement therapy. These come in several forms, including injections, implants, gels, and patches.

Just be aware that testosterone therapy comes with a host of potential side effects. According to Dr. Kim, testosterone therapy may increase platelets in your blood (which help with blood-clotting), increase enzymes in your liver (this may be an issue for those with chronic liver disease), or cause changes in cholesterol levels.

“The findings [on cholesterol levels] are inconsistent and that is why there is no standard approach at managing lipid changes in people on testosterone,” Dr. Kim explains. “Lipid profiles are very important for cardiovascular health, so it should be monitored in those taking testosterone.”

What’s more, medications aren’t the answer for every case of low testosterone levels. In some instances, lifestyle changes are your best move. “For example, if someone is obese with borderline low testosterone levels, and all other tests are normal, we would encourage weight loss with diet and exercise,” Dr. Kim says.

Younger men with low testosterone who are not obese need a diagnostic work up to determine the cause. Some men will require close investigation into puberty/fertility/family medical history and possible genetic testing. “Both younger and older men who are not obese and have low testosterone require endocrine work up, such as obtaining prolactin levels and possibly pituitary imaging,” she adds.

While research doesn’t directly say that exercise will increase testosterone, at least one study published in 2012 in the European Journal of Applied Physiology, which compared hormone differences among physically active and sedentary men, found that active men tend to have higher testosterone levels than sedentary men. Another study, published in 2004 in The International Journal of Neuroscience compared the testosterone levels in older males (age 68 and older) who exercised regularly to those who were sedentary. The exercising group showed significantly higher T levels than their sedentary counterparts. And finally, a study in the Journal of Endocrinological Investigation from 2012 found that intense bouts of exercise led to greater increases in testosterone post-workout than steady-state endurance exercise in endurance-trained men. However, this was both a small and short-term study—researchers didn’t check to see if and how long the increases in testosterone lasted.

Keep in mind, there’s also research that shows a different relationship between exercise and testosterone. For example, a systematic review and meta-analysis published in the Journal of Strength and Conditioning Research in 2021 found that exercise won’t affect resting free or total testosterone levels in insufficiently active, apparently healthy men. And researchers say more studies are needed.

The bottom line when it comes to increasing testosterone

For safety’s sake, you always want to steer clear of supplements that claim to boost T levels—even if you’re not competing in events that ban them. According to Piedmont Healthcare, testosterone supplements have a long list of unpleasant—even dangerous—side effects, including:

The FDA has even previously released a warning and label update for testosterone prescription products used for aging, calling out how they increase risk of heart attack and stroke.

Your best bet to return testosterone levels to normal is to work closely with your healthcare provider—skip the supplements and other “quick fixes”—so you can find what works for you and keeps you healthy.

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Lauren Bedosky

Lauren Bedosky is a freelance health and fitness writer who specializes in covering running and strength training topics. She writes for a variety of national publications, including Runner’s WorldPrevention, Experience Life and Women’s Running.