Medically reviewed by Vicky Davis, FNP
Written by Our Editorial Team
Last updated 8/12/2021
Low testosterone, or "low-T," is a surprisingly common condition that affects tens of millions of men around the world.
In fact, research has found that 10 to 40 percent of men have clinically low testosterone levels, including 20 percent of adolescent and young men.
Testosterone is an essential hormone for men (and women, albeit in very small amounts). At healthy levels, testosterone is responsible for everything from controlling your sex drive and energy levels to helping you gain strength and develop muscle tissue.
It also has a range of effects on your brain, helping to make you feel more confident, assertive and masculine.
Testosterone even affects things like your bone and heart health, making it an essential hormone not just for physical and mental performance, but also for general health.
There are numerous symptoms of low testosterone, ranging from lethargy to a decline in your physical strength.
Below, we’ve shared the 12 most common signs of low testosterone, all of which can indicate a potential testosterone deficiency.
We’ve also explained what you can do to treat your low testosterone, including testing options and common treatments for men with low-T.
Low testosterone is exactly what it sounds like -- lower than normal levels of the male hormone testosterone.
In men, low testosterone is often referred to as male hypogonadism, or testosterone deficiency syndrome (TD).
It’s a relatively common sexual health problem that can affect men of all ages and backgrounds.
A normal male testosterone level should be between 300 and 1,000 nanograms per deciliter of blood (ng/dL), or 10 to 35 nanomoles per liter (nmol/L).
The American Urology Association (AUA) defines low testosterone as any testosterone reading that’s below this level.
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).
Rapid weight loss. Losing a large amount of weight quickly, especially with a restrictive diet, may result in reduced testosterone production.
Injury or infection of the testes. Injuries that affect the testes, such as physical trauma or complications due to poor blood supply, may lead to 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 low testosterone.
Alcohol abuse. Excessive alcohol consumption can have numerous negative effects on your sexual health, including reduced production of testosterone and other reproductive hormones.
Internal organ damage. Damage to your liver (cirrhosis) and kidneys (renal failure) can affect your body’s production of testosterone.
Obstructive sleep apnea. Sleep has a large effect on testosterone production. Because of its impact on sleep duration and quality, obstructive sleep apnea can result in reduced testosterone production and an increased risk of low-T.
Other medical conditions. Other medical conditions, including HIV/AIDS, inflammatory conditions such as sarcoidosis and genetic conditions such as 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. On average, male testosterone levels decline by approximately 100 ng/DL every decade. This means that your likelihood of dropping below a normal testosterone level increases as you grow older.
As a man, testosterone plays a key role in your health and wellbeing. It’s responsible for most of your male secondary sex characteristics, including your voice, facial hair growth, muscle strength and bone structure.
It also plays a key role in your sexual function. Testosterone is vital for proper sperm production, and as an adolescent, it’s involved in many aspects of your male sexual development.
Below, we’ve shared 12 common physical and mental symptoms that are used to diagnose low testosterone in men.
Because testosterone is a hormone with several functions, low levels can often result in multiple symptoms.
If you’ve noticed any of the symptoms below, it’s important to talk to your healthcare provider about getting a blood test to check your testosterone levels.
Testosterone is one of the primary hormones responsible for making you feel motivated, alert and energetic.
When testosterone production is too low, it’s easy to feel fatigued and lethargic, even when you would normally be full of energy.
Low levels of testosterone are linked to chronic fatigue in men. If you often feel overly tired or lethargic, even after eating energy-rich foods or drinking coffee, there’s a chance that low levels of testosterone could be the culprit.
Testosterone is a powerful steroid, meaning it has a serious effect on your ability to gain muscle mass and improve your strength levels.
When your testosterone levels are low, it’s common for your muscles to shrink and your strength levels to decline.
Worse yet, lower-than-normal levels of testosterone may make it more difficult than usual to get back the strength and muscular size you’ve lost.
Studies of testosterone show that it produces a 27% increase in muscle protein synthesis when administered to men. Simply put, the more testosterone you produce, the easier it becomes to develop more muscle.
If you’ve noticed your strength levels decreasing, the sleeves of your shirts fitting loosely or your progress stalling in the gym, it could be because of low testosterone production.
Testosterone doesn’t just improve muscle strength -- it also plays a key role in promoting strong, healthy bones.
Men with low testosterone levels often have lower bone density, an issue that can increase your risk of bone fractures.
Common signs of low bone mass include a stooped back, decreasing height or stress fractures that seem to develop from everyday activity. Low bone density can be detected using a bone density test.
Low testosterone can affect your body’s production of blood cells, which may cause you to show a low blood count on a complete blood count (CBC) test.
Research has found that older men with low testosterone levels have a higher risk of developing anemia, a blood disorder in which the body has a low number of red blood cells.
Anemia can cause a range of symptoms, including dizziness, weakness, headaches, dry or pale skin, restless leg syndrome and a fast heartbeat.
As well as stimulating muscle growth, testosterone is also closely correlated with lower levels of body fat. People with high testosterone levels tend to be leaner, while people with lower levels of testosterone usually have a higher body fat percentage, especially around the abdominals.
A study of men on androgen deprivation therapy, which involves reducing testosterone levels to almost zero, showed a 22% increase in visceral fat around the abdominals.
In simple terms, low testosterone will give you a little more weight around the midsection. It can also increase your risk of developing coronary artery disease, as visceral fat can collect around your organs.
Combined with muscle wasting, this can have a serious effect on your physique, making it worth getting your testosterone levels checked if you notice this symptom.
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.
Specific parts of your body that usually 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 growth may feel firm and rubbery.
Research suggests that gynecomastia may occur due to an imbalance between estrogen and androgen hormones.
Testosterone plays a major role in spermatogenesis, the biological process through which your reproductive system creates sperm.
Although the precise relationship between testosterone and sperm count isn’t known, research has found that low testosterone levels and reduced sperm production may be linked.
For example, studies have found that approximately 15 percent of subfertile men have clinically low testosterone levels.
Because testosterone also plays an important role in the production of semen, low testosterone levels may also result in lower ejaculatory volume.
Another common symptom of low testosterone is a weaker-than-normal sex drive. When your testosterone levels are low, it’s easy to lose interest in sexual activity, even in situations when you would normally be highly interested.
The sex drive effects of low testosterone affect sexual intercourse and masturbation, meaning you might not think about sex much at all. As you’d expect, this can have a real effect on your relationships and personal life.
Luckily, this symptom is usually the fastest to reverse when your testosterone levels get back to normal, meaning you should notice an improvement soon after starting treatment.
Testosterone triggers 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’s more difficult to get and keep an erection than normal.
It can 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 are often much more subtle.
For example, you might be able to get an erection sometimes, 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.
Testosterone is responsible for more than just physical effects -- in men, it affects a variety of brain functions, including memory.
In fact, one of the most easily noticeable effects of low testosterone in men is "brain fog," or a general decline in memory and focus.
One study of men aged 70 years and above shows that age-related decreases in testosterone levels were closely correlated with cognitive decline.
As testosterone levels decreased, men were more likely to suffer from negative effects on cognitive functions
As well as affecting working memory, low testosterone levels can contribute to difficulty staying focused on specific tasks.
This doesn’t mean that forgetfulness is a sure-fire sign of low testosterone. However, if you’ve noticed a decline in your memory or your ability to concentrate, it could potentially be a signal that your testosterone level is lower than it once was.
In men of all ages, testosterone levels are closely correlated with confidence, mood and general quality of life.
When your testosterone levels fall below the normal level, it can have a negative impact on your mood and mental health.
One study from 2012 shows that treatment naïve hypogonadal men (men with low testosterone levels that did not seek treatment) showed more severe symptoms of depression, anxiety, poor quality of life and sexual dysfunction than similar men assigned to testosterone treatment.
Other studies show similar results -- that testosterone improves mood by a significant amount in men, with measurable decreases in negative emotional responses such as anger, irritability, and nervousness.
As always, dealing with frequent poor moods or other symptoms of depression isn’t necessarily a sign that you have low testosterone.
However, if you frequently feel tired, irritated, anxious or depressed and also have some of the other symptoms of low testosterone, it could be worth getting your testosterone levels checked.
Low testosterone is treatable. If you’re concerned that you may have low testosterone, it’s best to contact your healthcare provider or schedule an appointment with a doctor that specializes in male sexual or hormonal health, such as a urologist or endocrinologist.
To treat low testosterone levels, your healthcare provider may recommend testosterone therapy or suggest changes that you can make to your habits and lifestyle.
Testosterone replacement therapy involves increasing your testosterone levels through the use of artificial testosterone.
As part of TRT, your healthcare provider may prescribe testosterone in the form of an injectable medication, topical testosterone gel, tablets or skin patches.
Some forms of TRT involve a small testosterone pellet that’s implanted under your skin and replaced every few months.
Testosterone therapy is usually effective, but it can cause side effects. Your healthcare provider will work with you to monitor your blood pressure, lipids, prostate-specific antigen (PSA) levels and other important health markers during treatment.
Our guide to testosterone replacement therapy explains more about how TRT works, its effects, potential side effects and more.
It’s often possible to increase your testosterone levels naturally by making changes to your diet, activity level, habits and general lifestyle.
In general, a healthy lifestyle is an important part of healthy testosterone production. Habits like getting plenty of high quality sleep, eating a balanced, nutrient-rich diet and exercising regularly are all associated with healthy testosterone levels.
Your healthcare provider may suggest making lifestyle changes on their own, or in combination with testosterone therapy.
Our guide to increasing your testosterone levels shares natural techniques that you can use to increase your testosterone production.
Many of the symptoms above can occur without being caused by a testosterone deficiency. For example, it’s normal to feel tired or frustrated sometimes, especially if events in your personal or professional life have an effect on your mood.
It’s also normal to occasionally feel physically weaker than you normally would, especially if you make a change to your diet, lifestyle or physical activity levels.
As a general rule, you should consider getting your testosterone levels checked if you notice any of the symptoms listed above occurring frequently enough that you feel they aren’t just a normal occurrence.
Checking your testosterone levels is a quick and simple process. Most of the time, your levels can be checked with a quick and simple blood test that measures your free testosterone, total testosterone and levels of other hormones.
We’ve explained this process more, as well as the steps you can take to get your testosterone levels checked, in our guide to normal testosterone levels in men.
As a man, testosterone is essential for your health and wellbeing. If you have low testosterone, you may notice a variety of symptoms, from fatigue and lethargy to a weaker sex drive, loss of muscle mass and even problems focusing on tasks or remembering information.
If you’ve noticed any of these symptoms, it’s best to contact your healthcare provider and have your testosterone levels checked.
If your testosterone levels are below 300 ng/dL, your healthcare provider may prescribe TRT or suggest changes that you can make to your lifestyle to increase testosterone production.