Medically reviewed by Kristin Hall, FNP
Written by Our Editorial Team
Last updated 12/22/2021
Erectile dysfunction (ED) is a surprisingly common condition that many men prefer not to think about. Though there are a number of different risk factors that can contribute to erectile issues, low testosterone is frequently a contributing factor.
Testosterone is the male sex hormone produced in the testicles, and it affects everything from a man’s physical appearance to his sexual development and function.
If you’ve recently started to notice a drop in your sex drive, weaker erections or other symptoms of low testosterone, you may have looked into testosterone replacement therapy, or TRT.
Testosterone replacement therapy is a common form of treatment for men with low testosterone levels. It involves taking prescription testosterone, usually in the form of a patch, gel or injection, to supplement the natural testosterone that’s produced by your body.
According to the American Urological Association, about one in every five men above the age of 60 have low testosterone (low-T) levels. Low testosterone is even more common for older men, particularly men in their 70s and 80s.
It probably doesn’t surprise you to learn that erectile dysfunction is a common consequence of aging in men.
What you may not know, however, is that low testosterone can also affect younger men. In fact, research even suggests that around 20 percent of men aged between 15 and 39 have clinically low levels of testosterone.
Low testosterone can significantly affect your libido and sexual function, but solving the problem isn’t always as simple as just replacing the missing hormone.
Testosterone treatment comes with some significant risks, and it’s usually only recommended in very specific situations.
Keep reading to learn more about what low testosterone is, how using testosterone replacement therapy may help to treat it, as well as the risks and potential adverse effects that you should be aware of if you’re considering TRT as a treatment.
Low testosterone, or low-T, is exactly what it sounds like: testosterone levels that are below the typical range for men.
In healthy men, the normal range for testosterone levels is between 300 and 1,000 nanograms per deciliter (ng/dL). Testosterone deficiency is defined as any blood testosterone level that is below 300ng/dL of total testosterone.
As a man, testosterone plays a critical role in many important bodily functions. It fuels your sex drive, helps you to maintain healthy sexual function and plays a significant role in keeping your bones and muscles strong.
When your testosterone levels drop below the normal values, you may start to experience one or several of the following symptoms of low testosterone:
A weaker sex drive (low libido) and limited level of interest in sex
Difficulty achieving and/or maintain an erection firm enough for sex
Constant, ongoing feelings of tiredness, fatigue and low energy
Loss of body hair and reduced facial hair growth
Decrease in muscle mass and loss of physical strength
Changes in your body composition, such as an increase in body fat
Difficulty concentrating on specific tasks and a feeling of “brain fog”
Low mood, lack of interest in activities and other symptoms of depression
Reduced sperm count
Low testosterone levels can also cause more general symptoms, such as a poor memory or a general feeling that you’re not performing at your best. Many men seek help after developing several different symptoms related to low testosterone levels.
One confusing aspect of low testosterone is that the symptoms are easily mistaken for those of other conditions.
For example, many common diseases can cause you to lose muscle mass or strength -- even a common cold or flu. Other chronic health conditions, such as diabetes, can also produce similar symptoms.
If you think that you might have low testosterone, you can talk to your healthcare provider about getting a blood serum testosterone test.
This simple test checks your blood for its testosterone content. You’ll be able to see exactly how much total and free testosterone are circulating in your blood, allowing you to see if you have a normal or low testosterone level.
A variety of different factors can either cause or contribute to low testosterone levels, from age to chronic diseases. Common causes of low testosterone include:
Injury to your testicles. Some physical injuries can damage your testicles and prevent them from producing testosterone. Certain diseases, such as testicular cancer, may also affect your testicular function.
Obesity. If you’re currently overweight or obese, your body may not be able to produce testosterone efficiently. Research shows that adipose tissue (body fat) is linked to lower production of gonadotropin -- an important hormone for creating testosterone.
Side effects from medications. Some forms of medication, such as drugs used during chemotherapy, may affect your testicular function and prevent your body from producing normal levels of testosterone.
Age. Research shows that it’s common for testosterone levels to gradually decline as a natural result of the aging process. You may notice your testosterone levels starting to decline by a small amount as you enter your 30s, 40s and 50s.
Other diseases and medical treatments. Other medical conditions, such as glandular issues or certain autoimmune diseases, may affect your testicular function and result in low testosterone levels.
If you have noticeable symptoms from low testosterone, your healthcare provider may suggest using testosterone replacement therapy to increase your testosterone levels and improve your quality of life.
As we mentioned earlier, testosterone replacement therapy involves supplementing the natural testosterone produced by your body with synthetic testosterone. The idea is to bring your total testosterone levels into the normal, healthy range.
Testosterone replacement therapy can be delivered in one of several different ways, including the following:
Transdermal testosterone skin patches. These are applied to your skin, typically on your back, stomach, thighs or upper arm. The patch will gradually pass testosterone to your skin, which will be absorbed into your bloodstream.
Topical testosterone gels. This type of gel contains testosterone, which is transferred into your bloodstream via the skin. It’s important to be careful when using testosterone gel, as it can potentially transfer to other people through close skin-to-skin contact. Popular testosterone gels include Testim® and AndroGel®, which can be applied to the skin once per day.
Testosterone capsules. In some cases, your healthcare provider may give you tablets or capsules that contain testosterone. These often contain testosterone undecanoate, a long-acting form of testosterone.
Testosterone implants. Also referred to as testosterone pellets, these small implants are fitted under your skin. Most testosterone implants last for three to six months, after which a new implant needs to be fitted.
Intranasal testosterone. This form of testosterone is applied via your nose. It usually comes as a gel that’s pumped into your nostrils, allowing testosterone to quickly enter into your bloodstream.
Testosterone injections. Testosterone is available as an injectable medication. Your healthcare provider may inject the medication in their office, or instruct you on how to safely administer injectable testosterone at home.
Your healthcare provider may ask you about your needs and preferences, then choose the most appropriate form of testosterone for you.
If you feel uncomfortable with a certain form of testosterone (for example, you don’t like needles and would prefer not to use injectable medication), make sure to inform your healthcare provider so that they can prescribe a different form of testosterone.
If you have clinically low testosterone levels, using testosterone can offer real benefits for your health, physical function, sexual performance and general wellbeing.
Potential benefits of testosterone replacement therapy include:
Stronger sex drive.
Improved sexual function and erections.
Better mood and increased quality of life.
Increased muscle mass and bone density.
Since testosterone plays a key role in regulating your sex drive, it’s common to notice an increase in your level of interest in sex after you start testosterone replacement therapy.You may notice that you think about sex more often, get aroused more easily and have more sex with your partner.
Some aspects of your sexual function may improve with testosterone replacement therapy. For example, research shows that TRT can improve erections in men with mild erectile dysfunction.
Research shows that testosterone therapy improves mood parameters, including energy levels and positive feelings, amongst men with clinically low testosterone levels.
Testosterone replacement therapy may cause muscle growth and increased muscle strength, as well as increases in average bone mineral density.
Testosterone replacement therapy can have real benefits, especially if you have very low levels of testosterone.
However, it can also cause side effects, including some that may have a negative effect on your long-term health and wellbeing. In some cases, the risks associated with TRT may outweigh the rewards.
Potential side effects of testosterone treatment include:
Itching and/or irritation at the application site. Some forms of testosterone can cause itching or skin irritation. You may notice that your skin feels red or irritated when you use a testosterone patch or apply testosterone gel.
Pain and discomfort. If you use injectable testosterone, you may experience soreness after injecting your medication. Research shows that more than 80 percent of men have some degree of soreness after intramuscular injection of testosterone.
Risk of infection. Although uncommon, intramuscular injections can potentially result in infections. Your healthcare provider will inform you about how to inject your medication safely while minimizing the risk of transferring bacteria.
High red blood cell (RBC) count. Testosterone stimulates the production of red blood cells. You may notice an increase in your hematocrit and hemoglobin levels if you take a complete blood count test.This increase in red blood cell production may make your blood thicker, which can affect the flow of blood throughout your blood vessels and potentially cause blood clots.
Increased risk of cardiovascular disease. Testosterone replacement therapy is linked with a higher risk of experiencing cardiovascular problems, including stroke, heart attack and heart disease.
Acne breakouts. As an androgen, testosterone can stimulate the production of sebum and lead to acne breakouts. You may notice more whiteheads, blackheads and other types of acne after starting treatment with testosterone.
Male pattern baldness. Since testosterone is converted to dihydrotestosterone (DHT), the hormone that causes baldness in men, using testosterone may speed up hair loss if you’re genetically prone to male pattern baldness.
Sleep apnea. Research suggests that testosterone replacement therapy may aggravate obstructive sleep apnea (OSA), a condition in which the muscles inside your throat relax while sleeping, affecting your ability to breathe.
Although the scientific evidence is mixed, some experts believe that testosterone may contribute to benign prostatic hyperplasia (BPH), a form of non-cancerous prostate growth.
Because of this, testosterone products carry FDA warning labels notifying users of a risk of BPH and urinary retention.
If you have a history of prostate health issues, or if you’re above the age of 50, it’s important to keep track of your prostate health while using any form of testosterone.
Testosterone replacement therapy can have real benefits, but it’s something that you’ll need to think about carefully before deciding to take action.
If you decide that TRT is the right treatment for you, you should know that it won’t necessarily produce an immediate improvement. It may take as long as four to six weeks before you’ll be able notice any improvements in your low testosterone symptoms.
This is because it takes time for testosterone to build up in your bloodstream, allowing you to reach a normal testosterone level.
You should also know that once you start using testosterone, your body’s natural testosterone production will start to slow down.
Your body’s testosterone production is managed by the hypothalamic-pituitary-gonadal axis, or the hypothalamus, pituitary gland, and gonadal glands.
When your natural testosterone levels drop, the hypothalamic-pituitary-gonadal axis responds by producing more testosterone to bring you back to a normal testosterone level. However, if your testosterone levels increase, your body suppresses its natural testosterone production.
If you start testosterone replacement therapy, your body’s natural creation of testosterone will usually slow down or stop. This means that if you stop taking testosterone suddenly, you may experience the symptoms of low testosterone again.
Because of this, many men who start using testosterone replacement therapy continue using it for the long term.
Before starting TRT, you may want to consider increasing your testosterone levels naturally by making changes to your habits and lifestyle. You can do this by:
Exercising regularly, especially with a mix of aerobic exercise (running, cycling or other forms of endurance training) and strength training, such as weight lifting or body weight exercises.
Following a healthy diet that’s rich in fresh fruits and vegetables and contains a balance of healthy carbohydrates, proteins and fats.
Getting at least seven hours of high quality sleep per night, especially if you’re normally stressed, overworked or prone to undersleeping.
Our guide to increasing your testosterone production goes into greater detail about how these and other natural techniques can boost your testosterone levels without you having to rely on testosterone replacement therapy.
Low testosterone is a real medical condition that can have a significant impact on your sexual function, physical performance and quality of life.
If you’re considering testosterone replacement therapy, it’s important to talk to your healthcare provider first. They’ll be able to inform you about the potential benefits, as well as the possible health risks.
As part of testosterone treatment, you’ll need to check in regularly with a medical professional and make sure your health isn’t negatively affected.
Finally, if you’re considering testosterone replacement therapy because of ED, it’s always best to try erectile dysfunction treatments first. We offer a variety of FDA-approved ED medications that you can use to improve your erections and sexual performance.
Worried about your testosterone production? Our guide to testosterone levels in men explains what’s normal, as well as what you can do to get checked if you’re worried that you may have low testosterone production.