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Testosterone Replacement Therapy: Benefits, Side Effects & More

Kristin Hall, FNP

Reviewed by Kristin Hall, FNP

Written by Vanessa Gibbs

Published 12/21/2021

Updated 12/13/2023

Testosterone. Even the word alone sounds manly. 

For men, testosterone is important for sex drive, sperm production, energy and mood — to name just a few benefits.

When you have low testosterone, you might experience anything from low energy to erectile dysfunction (ED). 

Testosterone replacement therapy (or TRT) aims to fix some of these issues by topping up your natural supply of the hormone.

But TRT isn’t for everyone. It comes with serious risks, and it’s only FDA-approved for those with low testosterone caused by a medical condition — not aging. 

Read on to explore the benefits and side effects of TRT, as well as what you should know before starting the treatment.

So, what is TRT, anyway? Testosterone replacement therapy is exactly what it sounds like: treatment for men with low testosterone. 

You can get man-made testosterone in the form of a:

  • Patch

  • Gel

  • Pill

  • Implant

  • Injection

TRT can improve some of the symptoms of low testosterone by increasing the amount of the hormone in your system. 

You may have low testosterone (also known as low T or hypogonadism) due to: 

  • Damage to the testicles 

  • Obesity

  • Medical conditions

  • Aging

Testosterone levels start to decrease around age 30 to 40, but you can’t just get TRT if aging is the cause of your low testosterone. 

Older men with low testosterone have a higher risk of catabolic effects (muscle wasting or losing fat) linked to acute and chronic medical conditions. And it’s unclear how safe or effective TRT is for men with low testosterone due to aging.

The FDA (U.S. Food and Drug Administration) has only approved testosterone products for men with no or low testosterone due to a medical condition. For instance, genetic problems or chemotherapy can stop the testicles from producing testosterone.

You can get on TRT by speaking to a healthcare provider about your symptoms. They can test you for low testosterone and prescribe hormone therapy if the treatment is right for you.

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You may be a good candidate for TRT if you have low testosterone caused by a medical condition.

As noted, a healthcare provider can check your testosterone levels with lab tests to confirm if they are indeed low. The American Urology Association defines low testosterone as less than 300 nanograms per deciliter (ng/dL). 

Besides measuring your testosterone levels, a healthcare provider may want to talk about any symptoms you’ve been having, like low libido or erectile dysfunction. They might also ask about your medical history or do a physical exam and further health tests. 

Armed with all this info, a medical professional can diagnose you with low testosterone, figure out what could be causing it and determine whether the benefits of TRT outweigh the risks based on your symptoms, health conditions and risk factors. 

Who’s not a good candidate for TRT? Well, we’ve already mentioned how testosterone treatments aren’t FDA-approved for men with low T due to aging.

Beyond this, guys with untreated prostate and breast cancer (yes, men can get breast cancer, too) shouldn’t get TRT. And it should probably be avoided in men with severe untreated obstructive sleep apnea — when your breathing cuts off in your sleep. 

If you have erectile dysfunction but normal testosterone levels, TRT isn’t for you, either.

Also, if your testosterone levels aren’t low, TRT won’t be prescribed. More doesn’t equal better when it comes to testosterone, so boosting testosterone levels may not help your symptoms if they’re caused by other conditions. 

If you do have low levels, TRT will get you back to baseline. But there doesn’t seem to be any additional benefits in increasing testosterone levels further than that. 

Symptoms of Low Testosterone 

The symptoms of low testosterone include:

  • Loss of libido 

  • Erectile dysfunction (trouble getting or keeping an erection) 

  • Depression 

  • Lack of energy

  • Reduced cognitive function

  • Loss of muscle mass and strength

  • Osteoporosis (weak bones)

  • Irritability 

  • Loss of body hair 

  • Reduce beard growth

  • Obesity

It can be tricky to tell if you have low testosterone. After all, a lack of energy can be due to sleepless nights, loss of libido could boil down to relationship problems, and irritability might be because of, well…life.

Many men seek help after developing multiple symptoms of low testosterone. 

If you think you may be suffering from low testosterone, reach out to a healthcare provider. They can do blood tests to measure your testosterone levels and check if they’re low.

Learn more in our guide to the signs of low testosterone in men.

Common Causes of Low T 

Causes of low T include: 

  • Aging

  • Obesity

  • Metabolic syndrome, including high blood pressure

  • Infection

  • Medications like antidepressants

  • Autoimmune disease

  • Pituitary gland disease

  • Damage to the testicles

  • Removal of the testicles due to cancer

  • Chemotherapy or radiation

  • Ambiguous genitalia (when sex organs aren’t typical-looking)

  • Klinefelter syndrome 

  • Noonan syndrome

Lots of guys have low testosterone — and it gets more common with age. 

Studies use different metrics to define low levels, so numbers vary. But research shows low testosterone could affect 20 percent of men in their 60s, 30 percent in their 70s and a whopping 50 percent of those over 80 years old. 

Young guys don’t get away scot-free. Low testosterone can affect you at any age — it’s just rarer. Low testosterone may only affect around 1 percent of young men.

Also, low T is more common in men of all ages who are overweight or have diabetes. 

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Testosterone replacement therapy works by increasing the amount of testosterone in your system. You’ll take synthetic testosterone to make up for low levels of the natural hormone in your body.

It may take three to six months for symptoms to improve as testosterone builds up in your bloodstream.

There are several different types of TRT: 

  • Patches. Testosterone patches are applied to the skin, typically on the back, stomach, thigh or upper arm. Similar to a nicotine patch, a testosterone patch slowly releases testosterone into your skin, after which it absorbs into your bloodstream.

  • Gels. Gels also deliver testosterone into the bloodstream via the skin. You can apply a testosterone gel to your skin once a day. Take care not to transfer testosterone gel onto other people through skin-to-skin contact.  

  • Pills. Testosterone can also come in pills or capsules. These often contain testosterone undecanoate, a long-acting form of the hormone.

  • Intranasal testosterone. Picture a nasal spray for allergies. Gel or liquid intranasal testosterone is pumped into your nostrils to reach your bloodstream nasally.

  • Implants. Now we’re on to the more scary-sounding TRT treatments. Implants (also known as pellets) are implanted under the skin and slowly release testosterone into your system. They usually last three to six months before a new implant is fitted.

  • Injections. Testosterone can also be administered via an injection. You might get this done by a healthcare professional in a clinical setting or be taught how to administer your own injections at home.

Your healthcare provider can help you assess which type of TRT is right for you. 

Be sure to let them know if there’s a type of TRT you’d rather avoid. Perhaps you’re not a fan of needles (who is?), so you’d rather not have a testosterone injection, for example. 

There are many benefits of testosterone replacement therapy. 

TRT benefits include:

  • More energy  

  • Increased libido (sex drive)

  • Better sexual function (including improved erectile dysfunction) 

  • More lean muscle mass and increased strength 

  • Increased bone mineral density (BMD)

  • Improved depressive symptoms 

  • Weight loss

In terms of ED, a 2017 review found that TRT may help improve mild erectile dysfunction but not moderate or severe ED.

TRT and Erectile Dysfunction Medications

Phosphodiesterase 5 inhibitors (or PDE5 inhibitors) are a class of medication used to treat erectile dysfunction. Getting testosterone levels back to normal may help improve response to PDE5 inhibitors in men with low T who are unresponsive to the drugs.

You can learn more in our guide to low testosterone and ED.

TRT may also help treat hypoactive sexual desire disorder (loss of sexual desire) in postmenopausal women. It’s also sometimes used to create physical male sex characteristics in transgender people transitioning from female to male. 

It’s not all sunshine and rainbows. TRT can bring real benefits to your health and well-being if you’re suffering from symptoms of low testosterone — but it can also come with some ugly side effects and serious risks. 

The side effects of testosterone replacement therapy include: 

  • Acne

  • Redness, itching or a rash if you use gel or patches  

  • Swelling, bruising, pain and clotted blood under the skin if you use testosterone implants or pellets 

  • Reaction at the injection site if you use short-acting testosterone injections 

  • Allergic reaction if you use long-acting injections 

  • Pain and soreness at the injection site 

  • Infections if you use injections

  • Male pattern baldness

Quick note on male pattern baldness: Testosterone is converted into dihydrotestosterone (DHT), a hair-hating hormone that can cause baldness in men. If you’re genetically predisposed to androgenic alopecia (the clinical term for this type of hair loss), TRT could actually speed up hair loss.

The risks of TRT include:

  • Polycythemia (a high amount of red blood cells)

  • Prostate-related events — think prostate enlargement and prostate cancer

  • Reduction in high-density lipoprotein (HDL) cholesterol (aka “good cholesterol”) 

  • Obstructive sleep apnea (when you periodically stop breathing during sleep)

  • Worsening of prostate cancer or breast cancer 

  • Stroke or heart attack 

  • All-cause mortality (death as a result of any cause)

Speak to a healthcare provider if you experience any distressing TRT side effects. 

And get immediate medical attention if you experience: 

  • Trouble breathing

  • Shortness of breath 

  • Chest pain 

  • Weakness in one side of your body 

  • Slurred speech 

Here’s where things get complicated. Not everyone agrees on the risks of TRT. 

For instance, the American Urological Association says that, based on results from peer-reviewed scientific literature, there isn’t strong evidence that TRT increases or decreases the risk of cardiovascular events. 

In the end, it’s best to get personalized medical advice to find out if this type of hormone therapy is right for you. 

One final thing to keep in mind: If you use any kind of topical testosterone — like gels, creams or liquids — another risk of testosterone therapy is that you can transfer the drug onto other people. 

Be sure to cover the area and wash your hands after applying testosterone. You don’t want your partner, kids or anyone else you touch to unwittingly join you in your TRT journey.

TRT isn’t right for everyone. And, as with all medications, it comes with risks and side effects.

Before you start TRT, there are a few things to consider: 

  • Are you planning on having kids? If you plan on trying to conceive any time soon, let your healthcare provider know before starting TRT. Testosterone replacement therapy could disrupt normal sperm production, so your provider may recommend other treatment options or added treatment for sperm production.

  • TRT isn’t a quick fix. Unfortunately, one pill or patch isn’t enough to fix all your low T symptoms. Also, it might take up to six months for testosterone to build up and start working its magic.

  • You’ll need regular check-ups. You can’t just get a dose of testosterone and be on your way. You should be checked for heart disease and stroke before and while on testosterone. And you may need regular follow-ups with a healthcare provider to see if TRT is working.

  • You might be in it for the long haul. When taking synthetic testosterone, your body slows down or stops producing its own supply of the hormone. This means you may not be able to stop testosterone therapy once you start. If you suddenly stop TRT, symptoms of low testosterone could come back.

How to Boost Testosterone Without TRT

If hormone replacement therapy isn’t for you, don’t fret. TRT isn’t the only way to boost testosterone — lifestyle changes can also make a difference. 

Here’s how you can increase testosterone levels naturally: 

  • Exercise regularly. Aim for a mix of aerobic exercise (think running, cycling or swimming) and strength training (like weight lifting or bodyweight exercises).

  • Eat a healthy diet. Eat a diet rich in fresh fruits and veggies, complex carbs, proteins and healthy fats.

  • Try testosterone boosters. Natural testosterone boosters include ginseng, ashwagandha and fenugreek. (Psst — check out more foods that boost testosterone in our blog).

  • Get enough sleep. You know the drill. Aim for at least seven hours of solid shut-eye a night.

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If you’re experiencing symptoms of low testosterone, you might be eyeing up testosterone therapy as a treatment option. 

Here’s a quick recap of what you need to know: 

  • TRT can help improve some symptoms of low testosterone. It may increase your energy levels and libido and improve mild ED. Woo!

  • TRT isn’t for everyone. TRT is usually prescribed to men who have low testosterone due to a medical condition, not naturally low levels that come with age. 

  • Watch out for side effects and risks. TRT side effects range from acne to male pattern baldness, and risks can include greater odds of a heart attack or stroke. Not fun.

Talk to a healthcare provider if you’re considering hormone replacement therapy. They can assess if you have low testosterone levels, whether TRT is safe for you and the right treatment for your symptoms. They may even recommend other treatments to try before TRT.

For example, if you have ED, erectile dysfunction medications may be a safer and more effective treatment. You can get a prescription for several FDA-approved ED meds online through our sexual health platform.

10 Sources

  1. Could you have low testosterone? (n.d.).
  2. Osterberg, E. C., Bernie, A. M., & Ramasamy, R. (2014). Risks of testosterone replacement therapy in men. Indian journal of urology : IJU : journal of the Urological Society of India, 30(1), 2–7.
  3. What is Low Testosterone? (n.d.).
  4. Borst, S. E., & Mulligan, T. (2007). Testosterone replacement therapy for older men. Clinical interventions in aging, 2(4), 561–566.
  5. FDA Drug Safety Communication. (2018).
  6. Testosterone Information. (2015).
  7. Kim, S. D., & Cho, K. S. (2019). Obstructive Sleep Apnea and Testosterone Deficiency. The world journal of men's health, 37(1), 12–18.
  8. Petering, R. C., & Brooks, N. A. (2017). Testosterone Therapy: Review of Clinical Applications. American family physician, 96(7), 441–449.
  9. Jia, H., Sullivan, C. T., McCoy, S. C., Yarrow, J. F., Morrow, M., & Borst, S. E. (2015). Review of health risks of low testosterone and testosterone administration. World journal of clinical cases, 3(4), 338–344.
  10. Rizk, P. J., Kohn, T. P., Pastuszak, A. W., & Khera, M. (2017). Testosterone therapy improves erectile function and libido in hypogonadal men. Current opinion in urology, 27(6), 511–515.
Editorial Standards

Hims & Hers has strict sourcing guidelines to ensure our content is accurate and current. We rely on peer-reviewed studies, academic research institutions, and medical associations. We strive to use primary sources and refrain from using tertiary references. See a mistake? Let us know at [email protected]!

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards here.

Kristin Hall, FNP

Kristin Hall is a board-certified Family Nurse Practitioner with decades of experience in clinical practice and leadership. 

She has an extensive background in Family Medicine as both a front-line healthcare provider and clinical leader through her work as a primary care provider, retail health clinician and as Principal Investigator with the NIH

Certified through the American Nurses Credentialing Center, she brings her expertise in Family Medicine into your home by helping people improve their health and actively participate in their own healthcare. 

Kristin is a St. Louis native and earned her master’s degree in Nursing from St. Louis University, and is also a member of the American Academy of Nurse Practitioners. You can find Kristin on LinkedIn for more information.

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