Medically reviewed by Kristin Hall, FNP
Written by Our Editorial Team
Last updated 5/15/2021
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 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 happens 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 explained what you can do if you think you may have low testosterone and want to take action and treat it.
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.
Testosterone levels can vary significantly between individuals. In men, the standard range for testosterone is between 300 to 1,000 nanograms per deciliter of blood (ng/dL), or 10 and 35 nanomoles per liter (nmol/L).
It’s also common 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 to experience a gradual decline in testosterone production once you hit your 40s.
Although the decrease in testosterone is normal, it can occur at an abnormally fast pace for some men.
When testosterone levels drop below the healthy range, it’s often referred to as low testosterone, “low-T” or hypogonadism.
Low testosterone is a relatively common men’s health issue. Research published in Frontiers in Endocrinology notes that approximately 40 percent of men over age 45 have clinically low testosterone levels.
This change in testosterone production can lead to problems with sex drive, sperm production, muscle mass, fat distribution, bone density and even red blood cell production. While the relationship between testosterone and hair loss is not well understood, and misconnected.
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 type of testosterone accounts for a relatively small percentage of your total testosterone–and generally, only about one to two percent of your 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 testosterone bound to SHBG, this testosterone 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, or bound to albumin or 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 testosterone blood test.
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.
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 cause a more drastic reduction, particularly in younger men.
Contrary to popular belief, low testosterone only has a weak link to erectile dysfunction and isn’t a common cause of ED.
Androgens such as testosterone and dihydrotestosterone 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, 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 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 can cause sleep disturbances and disorders such as insomnia. If you have lower-than-normal levels of testosterone, you may find it difficult to fall asleep or stay asleep at 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.
As an anabolic hormone, testosterone plays a key role in building and maintaining muscle mass.
If you have low testosterone, you may experience a decrease in muscle mass and physical strength.
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, which may further compound the issue.
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.
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 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) and more serious problems such as an increased risk of blood clots, heart disease and enlarged prostate.
In some cases, TRT can contribute to cosmetic issues such as gynecomastia, a form of male breast growth.
You can learn more about the benefits and risks of TRT in our complete guide to testosterone replacement therapy.
If you are concerned about your testosterone levels but TRT is not for you, there are other options available.
While changing your habits may not be enough to treat clinically low testosterone, certain lifestyle changes may help increase your testosterone production naturally.
These include exercising more often (particularly performing high-intensity interval training, or HIIT), 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 testosterone levels provides more information about these tactics and their effectiveness.
Although it’s uncommon for low testosterone to cause erectile dysfunction, 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 may prescribe ED medication such as sildenafil (the active ingredient in Viagra®, 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 these medications and their effects.
Low testosterone is a common issue for men that can affect everything from sex drive to mood and cognitive function.
Although it’s natural to experience some decline in testosterone production over time, numerous treatment options are available that can help you maintain healthy testosterone levels as you enter your 40s, 50s, 60s and beyond.
Insider tips, early access and more.