Testosterone Replacement Therapy: Benefits, Side Effects, and What You Need to Know

Testosterone Replacement Therapy

Testosterone. The word alone sounds manly.

Testosterone is the quintessential male sex hormone that regulates a man’s sex drive, sperm production, bone health, metabolism, energy, mood, and much more. For this reason, it’s important you’re in range to have a healthy supply of it.

When you have low testosterone, you might experience a range of symptoms that might include low energy, weight gain, or erectile dysfunction (ED), among others.

In men with diagnosed low testosterone levels, Testosterone replacement therapy (TRT) aims to aid or fix some of these issues by topping up their natural supply of the androgen hormone.

But TRT isn’t for everyone. It comes with some risks, and you’ll need to meet certain requirements of testosterone deficiency (hypogonadism) before you can receive a prescription for TRT.

Read on to learn more about TRT, including benefits, risks, and potential side effects, plus what you should know before starting the treatment.

What Is Testosterone Replacement Therapy?

Basically, testosterone replacement therapy is exactly what it sounds like: It gives your body additional testosterone to make up for what it’s no longer producing on its own. The purpose isn’t to boost you beyond normal limits, but to restore healthy levels 

You can get man-made or synthetic (manufactured) testosterone in various formulations, such as:

• Patch

• Gel

• Intramuscular injection (the most common form of TRT)

• Nasal spray

Testosterone replacement therapy doesn’t work overnight, but gradual changes usually begin within a few weeks. As your hormone levels stabilize, you may start to feel more energetic, emotionally balanced, and notice relief from other symptoms. 

Some reasons to explain why you may have low testosterone (also known as low T or male hypogonadism) may include:

• Issues with the testicles

• Problems with hormones in the brain

• Chronic conditions such as obesity, diabetes, and sleep apnea

• Aging (testosterone naturally declines about 1 to 2 percent per year starting around age 30 to 40)

Who Can Use TRT?

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

The American Urology Association (AUA) defines low testosterone as less than 300 nanograms per deciliter (ng/dL). Low testosterone is diagnosed when two early-morning blood tests on different days show consistently low levels, along with symptoms of testosterone deficiency. Without this confirmed diagnosis, a healthcare provider typically won’t prescribe testosterone replacement therapy (TRT).

You can get on TRT by speaking to a healthcare physician — usually an endocrinologist or urologist — about your symptoms. They can test your levels of testosterone and prescribe hormone therapy if the treatment is right for you.

Besides measuring your testosterone levels, a healthcare provider may want to talk about any symptoms you’ve been having, like low libido (desire for sex) or erectile dysfunction. They should 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 the root cause, and determine whether the benefits of TRT outweigh the risks based on your symptoms and risk factors related to other health conditions you may have.

Who Shouldn’t Take TRT?

Testosterone treatments aren’t specifically approved by the FDA for men who have low T due to aging. However, doctors may still choose to prescribe it off-label when symptoms and low levels are present due to age. 

TRT may not be safe for men with the following health conditions:

• Untreated prostate and breast cancer (yes, men can get breast cancer)

• Severe, untreated obstructive sleep apnea

• Untreated heart failure

• Those trying to conceive

• People with ED who have normal testosterone levels

Ultimately, if your testosterone levels aren’t low, TRT won’t be prescribed. That’s because more doesn’t equal better when it comes to testosterone. Boosting your levels of the hormone may not help other symptoms if a different root cause is to blame. 

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

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

• Decreased bone density

• Increased breast growth (gynecomastia)

• Irritability

• Loss of body hair

• Reduced beard growth

• Obesity or increased body fat

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. Conditions like depression, hypothyroidism, and anemia can cause symptoms that mimic low testosterone. Since these issues often overlap, it’s essential to consult a healthcare professional to pinpoint the underlying cause and determine the most appropriate tests and treatment.

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 testosterone 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

• Disorders of sexual development

• Klinefelter syndrome

• Noonan syndrome

Does Low T Only Affect Older Men?

Lots of guys have low testosterone — and it gets more common with age. Testosterone levels start to decrease around age 30 to 40. Some research estimates that 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. Younger guys don’t necessarily get away scot-free, though. Low testosterone can affect you at any age — it’s just less common.

However, you can’t get TRT if aging is the cause of your low testosterone. In fact, it’s unclear how safe or effective TRT is for men with low testosterone due to this cause.

Also worth noting is that research finds low T to be more common in men of all ages who are overweight or have diabetes. And older men with low testosterone have a higher risk of catabolic effects (muscle wasting or losing fat) linked to acute and chronic medical conditions.

How Testosterone Replacement Therapy Works

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. Your healthcare provider will regularly check your testosterone levels throughout treatment to ensure they stay within a healthy range. With testosterone, more isn’t better. Levels that are too high can increase the risk of serious health problems. The goal is balance, not excess.

There are several forms of testosterone supplementation:

• Injections. Testosterone is commonly administered via an injection. A healthcare professional in a clinical setting might administer a dose, or you might learn how to inject yourself at home. These injections are usually administered into a muscle every 1 to 2 weeks.

• Transdermal 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. It’s important that you take care to not transfer testosterone gel onto other people through skin-to-skin contact.

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

• Buccal. Buccal testosterone is applied to the upper gum and remains in the mouth to deliver testosterone to your system. It is typically applied twice a day.

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

• Implants. Implants (also known as pellets) are placed under the skin and slowly release testosterone into your system. They usually last three to six months before needing to be replaced.

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. For instance, if you’re not a fan of needles, a testosterone injection might not be the best format for you.

Benefits of TRT

Testosterone replacement therapy offers many benefits, mainly by restoring normal testosterone levels and reversing the symptoms associated with low testosterone.

Potential TRT benefits include:

• More energy

• Increased libido (sex drive)

• Better sexual function (including improved erectile dysfunction)

• More lean muscle mass and increased muscle strength

• Better bone health (Increased bone mineral density (BMD)

• Improved depressive symptoms

• Weight loss and reduction in body fat

In terms of ED, a 2024 study involving men with low testosterone found that TRT led to an increase in sexual activity over 24 months compared to a placebo. While the therapy also boosted sexual desire and eased other symptoms of testosterone deficiency, it did not lead to meaningful improvements in erectile dysfunction (ED), a symptom often associated with low T. And a 2017 review found that TRT may help improve some symptoms of mild erectile dysfunction but not necessarily cases classified as moderate or severe.

TRT and Erectile Dysfunction Medications

Phosphodiesterase 5 inhibitors (or PDE5 inhibitors) are a class of medication used to treat erectile dysfunction. In men with low testosterone who don’t respond to PDE5 inhibitors, research has shown that restoring normal testosterone levels with TRT can help these medications work better.

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

If you’re trying to improve your erections while promoting your body’s ability to produce testosterone, consider learning about the Hims 2-in-1 Sex RX + Testosterone Support, which contains tadalafil (generic Cialis) for better erections and zinc for testosterone support.

Risks and Side Effects of TRT

It’s not all sunshine and rainbows with TRT. While the therapy can bring about benefits to your health and well-being if you’re suffering from symptoms of low testosterone, it can also pack some unwelcome side effects and serious risks.

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 after testosterone injections

• Allergic reactions

• Pain and soreness at the injection site

• Infections if you use injections

• Low sperm count and infertility

• Male pattern baldness

A quick note on male pattern baldness: Testosterone is converted into dihydrotestosterone (DHT), a 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.

Other risks of TRT include

• Polycythemia (a high red blood cell count, which can lead to blood clots)

• Prostate-related events: Although testosterone therapy isn’t thought to cause cancer, you should always talk to your doctor about your prostate health history.

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

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

• Worsening of prostate cancer or breast cancer

• Heart issues: Some studies suggest TRT might raise the risk of heart problems, especially in men with existing conditions, mainly with long-term TRT. The FDA recently removed the heart risk warning from testosterone labels, but still notes it may increase blood pressure. 

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

Speak to a healthcare provider if you experience any distressing TRT side effects or are concerned about specific risks.

Seek immediate medical attention if you experience any of the following:

• 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, according to the American Urological Association, based on results from peer-reviewed scientific literature, there isn’t strong evidence that TRT increases or decreases cardiovascular risk.

One final piece of intel 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, potentially opening them up to risks and side effects. Be sure to cover the area and wash your hands after applying testosterone. You don’t want your partner, kids, or anyone you touch to unwittingly join you in your TRT journey.

What to Consider Before Starting TRT

Before you start TRT, there are a few important considerations. Discuss them with your healthcare provider to determine if TRT is the right choice for you.

• 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 additional treatment for sperm production.

• TRT isn’t a quick fix. Unfortunately, one injection, pill, or patch isn’t enough to fix all your low T symptoms. Also, TRT might take up to six months to treat or resolve your symptoms.

• You’ll need regular checkups. You can’t just get a dose of testosterone and be on your way. You should be checked for pre-existing conditions such as heart disease. And you may need regular follow-ups with a healthcare provider to see if TRT is working as intended.

• 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 and potentially be more severe.

How to Boost Testosterone Without TRT

Your daily habits play a crucial role in your overall health and hormone balance. While lifestyle changes can help boost testosterone, they may not be enough for men with significantly low levels. Identifying areas where you can improve your routine can support healthy testosterone levels and enhance the effects of hormone replacement therapy. 

Here’s how you can support your testosterone production 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, veggies, complex carbs, proteins, and healthy fats.

• Try testosterone boosters. There’s no natural supplement that will magically boost testosterone on its own. But adding a few essential vitamins, minerals, and superfoods to your diet can support your body’s ability to make testosterone. Natural testosterone boosters include ginseng, ashwagandha, zinc, and fenugreek. (Psst, check out more foods that boost testosterone on our blog).

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

Understanding Testosterone Replacement Therapy

If you’re experiencing symptoms of low testosterone, you might be eyeing 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 symptoms of low testosterone, improve mild ED, and support increased energy levels, libido, and metabolism.

• TRT isn’t for everyone. TRT is prescribed to men who have low testosterone due to a medical condition. Healthcare providers might still prescribe TRT off-label for men with age-related low testosterone.

• Watch out for side effects and risks. TRT side effects range from acne to infertility to male pattern baldness, and risks can include greater odds of a heart attack or stroke.

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 or in addition to TRT.

For example, if you have ED, erectile dysfunction medications may be an effective add-on to improve erections. Find out if you’re a candidate for ED medications or other sexual health treatments by getting advice from a healthcare provider today.