Reviewed by Vicky Davis, FNP
Written by Our Editorial Team
Of testosterone’s many roles in human function and development (for men and women), most of us know it as the hormone that turns boys into men.
Testosterone is responsible for several key functions in your body, from the development of your voice, hair and genitals to maintaining your sexual function and fertility.
It also plays a significant role in your mental health and wellbeing, helping to manage everything from your mood to your level of interest in sex.
The male body produces testosterone at a rate specific to each individual. But what can happen when your body doesn’t produce enough?
Below, we’ve listed several signs that you may experience if your testosterone levels are on the lower side of normal, from changes in the way you think and feel to physical changes that might affect your muscles, bones and even your sexual performance.
We’ve also talked about what you can do if you think you might have low testosterone and want to take action and treat it.
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Testosterone is the primary male sex hormone. It belongs to a class of hormones referred to as androgens.
Although testosterone is present in both men and women, it’s produced in far higher amounts in men.
In men, testosterone is produced in the testes, where what’s called leydig cells work to convert cholesterol into testosterone. Your pituitary gland — a small gland at the base of your brain that produces other hormones — also plays a key role in the process of testosterone production. See also: can you get an erection without testes?
Testosterone levels can vary significantly between individuals. In men, the standard range for testosterone is between 300 and 1,000 nanograms per deciliter of blood (ng/dL), or 10 and 35 nanomoles per liter (nmol/L).
It’s normal for testosterone levels to fluctuate over the course of the day. Most men experience their highest testosterone production in the morning, with the testes producing less testosterone at night.
Most men have healthy, optimal testosterone levels when they’re young. However, it’s common and normal to experience a gradual decline in your body’s overall testosterone production once you reach your 40s, 50s, 60s or beyond.
Although this gradual decrease in testosterone production is common and normal, it can occur at an abnormally fast pace for some men.
When testosterone levels drop below the healthy range for men, it’s usually often referred to as low testosterone, “low-T” or hypogonadism.
Low testosterone is a relatively common men’s health issue. Research published in the journal Frontiers in Endocrinology notes that approximately 40 percent of men over the age of 45 have clinically low testosterone levels.
This decrease in testosterone production can lead to problems with sex drive, sperm production, muscle mass levels, fat distribution, bone density and even red blood cell production.
Low testosterone is exactly what it sounds like — lower than normal levels of the male hormone testosterone.
As we mentioned above, there’s no one-size-fits-all level at which men’s testosterone levels are thought of as “normal.” Instead, testosterone levels exist across a range, with any level between 300 and 1,000 nanograms per deciliter of blood considered healthy.
The American Urology Association (AUA) defines low testosterone as any testosterone reading that’s below this level, accompanied by symptoms, following two testosterone levels tests taken on separate dates.
A variety of different factors can contribute to low testosterone production in men, from your diet and lifestyle to your age. Common causes of and risk factors for low testosterone include:
Being overweight or obese. Obesity is associated with low testosterone. Research has found that obesity is linked to a reduction in total testosterone, as well as reduced levels of hormones such as follicle stimulating hormone (FSH).
Injury or infection of the testes. Injuries that affect the testes, such as physical trauma or complications due to poor blood supply, may result in low testosterone. Infections that affect the testicles, such as orchitis, may also affect testosterone production.
Diabetes. Research shows that men with type 2 diabetes are more likely to develop low testosterone.
Metabolic disorders. Certain metabolic disorders, such as hemochromatosis (extra iron buildup in the body) can cause or contribute to testosterone deficiency.
Alcohol abuse. Excessive alcohol consumption can have numerous negative effects on your sexual health, including reduced production of testosterone and other reproductive hormones.
Obstructive sleep apnea. Sleep has a large effect on testosterone production. Because of its impact on sleep duration and quality, obstructive sleep apnea may result in reduced testosterone production and an increased risk of low-T.
Other health conditions. Other medical conditions, including HIV/AIDS, inflammatory conditions such as sarcoidosis and chromosomal conditions like Klinefelter syndrome, can contribute to low testosterone levels in men.
Anabolic steroid abuse. Anabolic steroids used to increase muscle mass and strength can disrupt your natural testicular function, potentially causing testicular atrophy (loss of testicular size) and reduced testosterone levels.
Aging. It’s common for your testosterone levels to decline as you age. This means that your risk of dropping to less than a normal testosterone level will increase as part of the normal aging process.
If you’ve ever searched for information about testosterone levels, you may have come across terms like “total testosterone,” “free testosterone” and “bioavailable testosterone.”
These terms refer to testosterone that’s either freely floating in your blood or bound to certain proteins.
Free testosterone, as its name suggests, freely circulates in your blood without being bound to any proteins.
This form of testosterone accounts for a relatively small amount of your total testosterone, and usually, only around two to three percent of your body’s total testosterone is in this state at any particular time.
Most of the testosterone in your body is bound to a protein called sex hormone binding globulin, or SHBG.
This testosterone isn’t free to access your cells and is generally thought of as inactive. However, it’s still measured as part of your total testosterone.
Finally, about half of the leftover testosterone in your bloodstream is bound to albumin, a protein that’s produced by your liver. Unlike the testosterone bound to SHBG, testosterone that’s bound to albumin can freely access cells and work its effects throughout your body.
Total testosterone is a term used to refer to all of the testosterone that’s circulating in your blood, whether it’s free, bound to albumin or bound to SHBG.
Free testosterone refers only to testosterone that’s freely circulating without being bound to any type of protein. Finally, bioavailable testosterone refers to testosterone that’s free or bound only to albumin.
It’s important to keep these different types of testosterone in mind if you ever get a test to check your blood testosterone levels.
If your total testosterone level is within the healthy range but you’re still experiencing symptoms of low testosterone, it could be that your bioavailable testosterone levels are low.
Low testosterone can cause numerous symptoms, from changes in your muscle mass and bone health, to issues that affect mood, energy and sexual function.
If you have low testosterone, you may notice one or more symptoms. These can vary in severity from mild issues to serious ones that contribute to medical conditions or affect your quality of life as a man.
We’ve listed several of the most common signs of low testosterone in men below, along with information on how each issue may affect your health and wellbeing.
One of the most common signs of low testosterone is a low sex drive. You may notice that you have less interest in sexual activity or that you don’t spend much time thinking about sex.
Many men notice a decline in sexual desire with age, but low testosterone can produce a more drastic reduction, particularly in younger men.
Although the relationship between testosterone levels and erections isn’t totally clear, evidence suggests that low testosterone levels can affect your sexual function and contribute to common male sexual performance issues such as erectile dysfunction.
Research suggests that testosterone can trigger the release of nitric oxide, which is an essential molecule for developing and maintaining an erection. This means that when your testosterone levels are low, it might become more difficult to get and keep an erection than normal.
It could also mean that spontaneous erections — the erections you get while you’re sleeping, for example — don’t happen anymore, or at least not as frequently as they normally would.
While ED is typically associated with a complete inability to get an erection, the symptoms of ED are often much more subtle.
For example, you might be able to get and maintain an erection occasionally, but not every time you and your partner want to have sex. Or, you might be able to get hard, but not maintain your erection for the entire time you have sex.
Since erectile dysfunction can occur for a variety of reasons, you shouldn’t rush to assume you have low testosterone if you have difficulty getting or maintaining an erection.
However, combined with other symptoms listed above and below, erectile dysfunction could be a sign of a testosterone-related issue.
Androgens such as testosterone and dihydrotestosterone (DHT) play a major role in stimulating your prostate and seminal vesicles, which are responsible for producing semen.
Low testosterone may also affect your body’s ability to produce sperm, potentially resulting in a reduced sperm count. In some cases, low testosterone can even result in infertility.
In addition to producing a lower amount of sperm, your testicles may become physically smaller as your testosterone levels decline.
One study published in the journal Andrologia found an association between lower-than-normal levels of testosterone and reduced testicular volume.
However, this doesn’t necessarily mean that your testicles will shrink by any significant amount if you’re affected by low-T.
Testosterone plays a major role in hair growth. If you have low testosterone, you may notice that your body hair doesn’t grow as much as it used to.
In addition to affecting body hair growth, low testosterone may also reduce the growth of your facial hair.
Low testosterone may cause sleep disturbances and disorders such as insomnia. If you have lower-than-normal levels of testosterone, you might find it difficult to fall asleep or stay asleep throughout the night.
Because low testosterone can affect your sleep quality, you may feel tired and less motivated to engage in certain activities throughout the day. Some men with low testosterone report feeling fatigued, even after getting a healthy amount of sleep.
Others report symptoms such as reduced physical endurance, which may make some tasks more physically taxing and difficult to perform.
Low testosterone levels may increase your risk of experiencing hot flashes — sudden feelings of warmth that affect your face and chest. These may be accompanied by sweating, flushing and other symptoms.
As an anabolic hormone, testosterone plays an important role in building and maintaining your muscle mass. If you have low testosterone levels, you could experience a decrease in muscle mass and physical strength.
This means that certain exercises, such as weightlifting and calisthenics, may be more difficult to perform than in the past.
It’s important to keep in mind, however, that changes in your muscle mass don’t always cause changes in strength or muscle function.
In addition to losing muscle mass, you may find your body composition changing and your fat level increasing.
Research shows that obesity reduces testosterone, and that waist size is a strong predictor of low testosterone. This may further compound the problem, with low testosterone contributing to an increase in your body fat levels and increased fat affecting your testosterone production.
Increased fat from low testosterone levels may have other negative effects on your health. For example, low testosterone levels are also associated with high lipid levels, high blood pressure and other issues that may increase your risk of cardiovascular disease.
Testosterone is an important hormone for bone growth and maintenance. If you have low levels of testosterone, you may be more likely to suffer from bone mass loss. This may increase your risk of developing fractures.
Over time, the effects of low testosterone on your bones can result in skeletal diseases such as osteoporosis.
Not only does testosterone play a role in many physiological processes, but it can also have an impact on your cognitive function, performance and mood.
If you have low testosterone, you may have a higher risk of developing mood disorders such as depression. Low testosterone can also lead to difficulty concentrating and a tough time finding words to use in conversation.
In addition to affecting your ability to concentrate or verbalize your thoughts, low testosterone is often linked to memory issues. Some men with low testosterone report experiencing “brain fog” and poor memory.
Combined with the other cognitive symptoms listed above, this may have a negative effect on your workplace or academic performance.
Despite all this, research has not found a clear link between testosterone supplementation and an improvement in memory in men with low testosterone.
Testosterone plays a key role in your body’s creation of red blood cells, which are essential for delivering oxygen to organs and removing carbon dioxide from your body.
Research shows that older men and women with low testosterone have lower red blood cell counts and an increased risk of developing anemia.
Testosterone and other androgens play important roles in the development and growth of your facial and body hair.
If you’re deficient in testosterone, you may notice that your body hair doesn’t grow to the same level or thickness as it previously did. Some parts of your body that typically have hair, such as your armpits or genitals, may start to lose hair.
Low testosterone levels can sometimes result in gynecomastia — a form of breast growth that affects men.
Gynecomastia can cause your nipples to become swollen or tender. You may be able to feel a growth in the glandular tissue behind one or both of your nipples. In some cases, this breast tissue growth may feel firm and rubbery.
Research suggests that gynecomastia may occur due to an imbalance between estrogen and androgen hormones.
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As you get older, your hormone levels naturally change. For women, production of the primary female hormone estrogen drops in menopause, causing a range of physical changes.
For men, although the decline isn’t quite so sudden or significant, it’s common for testosterone levels to gradually decrease over time.
If you think that you might have low testosterone, it’s best to bring this up with your healthcare provider or schedule an appointment with a urologist.
They’ll be able to check your testosterone levels, as well as your levels of luteinizing hormone (LH), prolactin, hemoglobin and other related hormones, with a simple blood test.
If your total testosterone level is below 300 ng/dL, your healthcare provider may suggest using testosterone replacement therapy (TRT) to increase your testosterone levels.
Testosterone replacement therapy, or testosterone therapy, is a form of hormone replacement therapy for men.
This form of treatment involves the use of artificial testosterone to increase testosterone levels and treat the symptoms of low-T.
The supplemental testosterone used for TRT comes in several forms, including skin patches, topical gels, tablets, implants and injectable testosterone.
Testosterone replacement therapy has real benefits, but it can also cause side effects. These include minor issues such as skin irritation (particularly with gels and liquids), as well as more serious issues such as an increased risk of blood clots and heart health problems.
In some cases, testosterone replacement therapy can also contribute to cosmetic issues such as gynecomastia, a form of male breast growth.
TRT may also be unsafe if you have a history of prostate cancer, breast cancer or other forms of cancer that are affected by androgen levels. If you’ve previously received cancer treatment, it’s important to inform your healthcare provider before considering testosterone treatment.
You can find out more about the benefits, risks and potential side effects of TRT in our complete guide to testosterone replacement therapy.
If you are concerned about your testosterone levels but TRT isn’t quite right for you, there are other options available.
While changing your habits may not be enough to treat clinically low testosterone, making some lifestyle changes may help increase your testosterone production naturally.
These include exercising more often, minimizing stress, eating a testosterone-boosting diet and, if you’re overweight or obese, making an effort to shed excess body fat.
Our guide to increasing your testosterone levels goes into more detail about how you can adjust your habits and lifestyle for better testosterone production.
Although it’s generally uncommon for low testosterone to cause severe or persistent ED, some men with low-T may find it difficult to get or maintain an erection.
If you have erectile dysfunction and low testosterone, your healthcare provider might prescribe an ED medication such as sildenafil (the active ingredient in Viagra®, as well as generic Viagra) to make it easier for you to get and maintain an erection.
Our guide to the most common ED treatments goes into more detail about how ED medications work, as well as their potential side effects.
Low testosterone is a common problem for men that can affect everything from your sex drive to your mood, energy levels and cognitive function.
Although it’s natural to experience some decline in testosterone production over time, numerous treatments are available that can help you to maintain healthy testosterone levels if you develop low-T in your 30s, 40s, 50s or beyond.
If you’ve started to notice one or several of the common symptoms of low testosterone, it’s best to talk to your healthcare provider.
They’ll be able to check your testosterone levels and, if appropriate, provide a treatment plan or refer you to a urologist for expert help.
If you don’t notice any other signs of low-T but find it difficult to get or maintain an erection, you can access treatment for ED by taking part in an online erectile dysfunction consultation with a healthcare provider.
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Dr. Vicky Davis is a board-certified Family Nurse Practitioner with over 20 years of experience in clinical practice, leadership and education.
Dr. Davis' expertise include direct patient care and many years working in clinical research to bring evidence-based care to patients and their families.
She is also an active member of the American Academy of Nurse Practitioners.