Testosterone is a hormone that your body needs. It helps you keep your muscle mass, hair on your face and body, sex drive, and the ability to make red blood cells. So when your levels are low, which is also called “low T,” you can have a lot of different side effects.
When you have low T, you might need testosterone therapy to raise your levels and make your symptoms go away.
“Testosterone therapy adds to or replaces an important hormone that your body makes naturally,” says Darshan Patel, M.D., assistant professor of urology at the Men’s Health Centre at the University of California, San Diego.
If you don’t have enough testosterone, the androgen receptors in your body and brain don’t work. This can cause low libido, weak erections and orgasms, an inability to build muscle mass, low energy, or just a feeling of sadness. When your body doesn’t make enough of this hormone, it leads to a condition called hypogonadism.
Low testosterone can be fixed with testosterone replacement therapy. If your doctor gives you testosterone therapy, you’ll probably start to notice changes, both big and small, good and bad. There are a few things you should know about testosterone therapy, even if you don’t see or feel them all right away.
What is testosterone therapy?
Hypogonadism can cause some of the effects of testosterone therapy to go away.
Ryan Smith, M.D., an associate urology professor and urologic microsurgeon at the University of Virginia Health who specialises in men’s health, says that your testosterone levels will be tested to see if you are a good candidate for the therapy.
Dr. Smith says that they will take two blood tests in the morning on different days, when testosterone is at its highest. Some say low is under 300 nanograms per deciliter (ng/dL), while others say 264. Doctors also take into account any symptoms you have, such as a low libido, feeling tired, or just not feeling like yourself.
There are many ways to treat low testosterone, says Dr. Patel, including injections, gels that go on the skin, cream patches, pellets that go under the skin, pills, and nasal sprays. Each has a different set of side effects.
Dr. Tamler says that the right treatment for you depends on what you want, what your situation is, and what your insurance will pay for.
Why you should take testosterone under a doctor’s supervision
Most of the time, you can get testosterone online without a prescription. But Justin Dubin, M.D., a urologist and men’s health specialist at Memorial Healthcare System, says that taking it without a doctor’s permission and supervision can be dangerous.
In a 2022 study that Dr Dubin helped write, researchers found that many online platforms don’t offer testosterone therapy in line with the recommendations of the American Urological Association and the Endocrine Society. Using a secret shopper, they found that the platforms offered therapy to men who didn’t meet the guidelines and didn’t talk about the risks or benefits of testosterone therapy.
Working with a doctor makes sure you only get testosterone when you need it and take the right amount. Then, they can work with you to make sure your testosterone levels respond in the right way. Every six months, they like to check on you again to make sure you aren’t having any bad side effects.
Testosterone therapy side effects
Dr. Smith says that it can take a few weeks to a month or two for your symptoms to get better after you start testosterone replacement therapy. Here are some of the side effects of testosterone therapy, both good and bad:
1. Effect of testosterone: Your sex drive jumps
When you’re low on testosterone, you might notice your sex drive dip. Testosterone replacement can activate the androgen receptors in the part of your brain that controls desire, says Abraham Morgentaler, M.D., clinical associate professor of urology at Harvard Medical School; and author of Testosterone for Life.
He says that one of the best things about testosterone replacement therapy is that it helps men get their sexual drive back. T-therapy might also improve the quality of your erections.
This isn’t the only piece of the puzzle, though. Healthy nerves and blood flow are also important for getting an erection. So, this means that testosterone therapy isn’t a cure for impotence by itself.
2. Effect of testosterone: It’s easier to build muscle
Dr. Morgentaler says that starting T-therapy can help build more muscle mass because muscles respond to testosterone. Because testosterone stimulates growth by turning on the androgen receptors in muscle tissue.
Of course, to get the most out of this benefit, you will also need to work on your strength. He warns that testosterone replacement therapy might make your muscles stronger, but it won’t make you a bodybuilder on its own.
Some men also say they’ve lost weight. Even though testosterone doesn’t directly cause fat loss, the increase in muscle mass may be a factor. The more muscle you have, the higher your basal metabolic rate (BMR), which means your body will burn more calories even when you’re not doing anything.
3. Effect of testosterone: Your energy levels can soar
Low T often makes people feel tired. “And when we treat them, a lot of men will say that their energy has gotten better,” says Dr. Morgentaler.
Researchers aren’t sure yet how exactly testosterone affects energy, but he says it’s thought that it might have something to do with your mitochondria, which make energy in your cells. “Testosterone turns them on,” the theory goes, so they can make more of the energy that the cells need.
Dr. Tamler also says it might have something to do with androgen receptors. “They can get tired if they don’t get enough input,” he says. So bringing the level of testosterone back up can help fix this.
4. Effect of testosterone: Your mood can improve
No one knows for sure why testosterone has such a big effect on mood, since “the brain is a complicated thing,” as Dr. Tamler puts it. But the positive effects of T therapy on mood could change your whole life.
After 12 months of testosterone therapy, the number of men with moderately severe to severe depression symptoms dropped from 17% to 2%, according to a study published in The Ageing Male. And the T Trials, a large randomised trial of testosterone, showed that men’s moods were better when they took T than when they took a placebo.
5. Effect of testosterone: It can affect your fertility
The most important thing to know about testosterone therapy is how it affects your sperm production and fertility. Testosterone therapy can make you less fertile and reduce the number of sperm you make.
It could also change how big your testicles are. “Most of the size of the testicle is used to make sperm,” says Dr. Morgentaler. “When you make less sperm, the testicles get smaller.”
After treatment ends, sperm production may or may not go back to normal, says Dr. Kaminetsky. A 2017 study in Fertility & Sterility found that the chances of normal sperm recovery went down with age and the length of T-therapy.
6. Effect of testosterone: Your feet and ankles may swell
Dr. Morgentaler says that testosterone can make your body want to hold on to extra fluid, which can cause your feet and ankles to swell a little bit.
He says this isn’t a big deal for most people and is more likely to happen if you take a treatment that isn’t taken every day, like an injection, where you get a higher dose of T at once.
7. Effect of testosterone: Your skin type may change
Dr. Morgentaler says that testosterone replacement therapy may change your skin type, either for the better or for the worse.
Oil production can go up because of testosterone, which isn’t always a bad thing. It’s good for skin health, so you may end up with a better complexion. But if too much oil builds up, it can cause spots.
Dr. Morgentaler says this doesn’t happen very often, and men with a history of acne are most likely to have it.
Most skin changes happen when you get a high dose all at once, like when you get an injection.
8. Effect of testosterone: Your breasts may enlarge
Some testosterone is changed into estradiol, a type of oestrogen, in all men, whether they take T or not. And in men who naturally have more breast tissue, the T they take that gets turned into estradiol could cause this tissue to grow.
Dr. Morgentaler says this is called gynecomastia, and it doesn’t happen as often as other side effects. If this happens, your doctor will probably stop your treatment for a month or two to let your breast tissue go back to normal. Then, he or she will start you back on T along with a drug that stops testosterone from being turned into estradiol.
9. Effect of testosterone: You can transfer the hormone to others
Dr. Patel says that if you use topical testosterone therapy, you should worry about transference, especially to female partners or children. Testosterone from gels or creams can be absorbed by someone else through skin-to-skin contact or through your clothes.
Dr. Smith says, “You really need to be careful to wash your hands well and not let anyone else get sick.”
When children come in contact with too much testosterone, it can change their genitalia, cause pubic hair to grow early, and make them act more aggressively.
Is Testosterone Therapy Safe?
Testosterone replacement therapy is safe and approved by the U.S. Food and Drug Administration for men with a testosterone deficiency, Dr. Patel.
And, it’s safe as long as you follow your doctor’s orders and don’t seek it out on your own. “It requires regular monitoring by your doctor,” he adds.
While there are several myths about testosterone therapy and the risk of cardiovascular disease and prostate cancer, there’s no conclusive evidence, Dr. Patel emphasizes. “This is an ongoing area of research.”
Alexa is a Denver-based contributor who covers all things lifestyle, wellness, travel, home, and beauty. When she’s not writing, you can find her sweating it out at boxing or Pilates, planning her next travel adventure, or drinking red wine.