Low testosterone or testosterone deficiency, also known as hypogonadism, is a condition in which patients develop symptoms such as low sex drive, erectile dysfunction (ED), and fatigue because the body doesn’t produce enough testosterone.
Testosterone is the primary androgen — or male sex hormone — in your body. Low testosterone affects up to 39 percent of adult men in the US over the age of 45, and becomes increasingly prevalent as men age.
Some men have medical conditions that impair testicular testosterone production, such as Klinefelter’s syndrome. This type of testosterone deficiency is known as primary testicular failure or primary hypogonadism.
Other men, such as men with obesity or pituitary dysfunction, develop low testosterone because the hormonally active parts of the brain (the hypothalamus and the pituitary) do not produce enough hormones to stimulate the testicles. This type of testosterone deficiency is sometimes called secondary hypogonadism.
Testosterone levels increase in adolescence after puberty and into early adulthood, and naturally decline over time, usually starting in a man’s 40s or fifties. However, this drop now seems to be happening even earlier. Research shows men under 40 have lower testosterone than preceding generations.
But what’s causing this trend? And what does it mean for your health?
There’s no sex hormone more synonymous with being male than testosterone.
As a fetus, testosterone drives the development of your prostate, penis, and testicles. During puberty, the hormone is responsible for deepening your voice, helping you grow body hair, increasing the size of your muscles and bones, regulating your sex drive, and supporting sperm production.
Though women also produce testosterone, men produce 20 to 25 times more in comparison, and about 95 percent of it is made in the testicles. But the testes don’t work alone — they rely on messages from your brain.
The process goes like this:
The hypothalamus produces and releases gonadotropin-releasing hormone (GnRH).
GnRH nudges the pituitary gland to produce luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
FSH then signals the Sertoli cells in your testes to make sperm, while LH calls on the Leydig cells (also in the testes) to make testosterone.
Testosterone production can be compromised if something happens to one of the main players in this process — the hypothalamus, the pituitary gland, or the testes.
If testosterone production is compromised, you may see changes in many of those processes that testosterone regulates, including your body hair, sex drive, sperm production, and more.
The standard range for normal testosterone (eugonadal) levels in men is 300 to 1,000 nanograms per deciliter (ng/dL). But it’s totally normal for your testosterone to fluctuate throughout your life and even throughout the day.
Some experts argue that 300 ng/dL is not an accurate cut-off for normal testosterone levels because the guideline was based on older men.
However, a recent study of men ages 20 to 44 suggested the following ranges were more accurate based on different age groups:
20-24 years old: 409-558 ng/dL
25-29 years old: 413-575 ng/dL
30-34 years old: 359-498 ng/dL
35-39 years old: 352-478 ng/dL
40-44 years old: 350-473 ng/dL
Although the American Urological Association (AUA) defines low testosterone as a total testosterone level of less than 300 ng/dL, it’s important to note that low testosterone isn’t just about a number. A clinical diagnosis of testosterone deficiency should only be made when patients have low levels of testosterone combined with symptoms and/or signs of low T.
Low testosterone symptoms in men vary widely, especially across different age groups. If you have low testosterone, it can lead to problems with sex drive, sperm count, muscle mass levels, fat distribution, bone density, and even red blood cell production. These signs and symptoms may vary in severity and affect the quality of your life.
Some of the most common signs and symptoms of low testosterone in men include:
Reduced sex drive
Erectile dysfunction (ED)
Low sperm count and quality
Testicular shrinkage
Sleep disturbances
Low energy levels
Hot flashes
Loss of muscle mass
Increased body fat
Decreased bone density
Mood changes
Memory trouble
Reduced red blood cell count (anemia)
Less body hair
Gynecomastia (male breast development)
One of the most common signs of low testosterone is a low sex drive (aka low libido). You may have less interest in sexual activity or realize you’re not spending as much time thinking about sex as you used to.
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 precise relationship between erection quality and testosterone levels isn’t clear, studies show that men with low testosterone have a higher prevalence of erectile dysfunction (ED) compared to men with normal levels. Multiple controlled trials have also shown that erectile function improves when testosterone therapy is given to men with low T.
What role might testosterone play in erections? Some research suggests that testosterone helps regulate the production of nitric oxide, an essential molecule for developing and maintaining an erection. Consequently, when your testosterone levels are low, you may have trouble performing.
It could also mean spontaneous erections (like waking up with "morning wood") don’t happen anymore — or, at least, not as frequently as they normally would.
Since erectile dysfunction can occur for numerous reasons, you shouldn’t rush to assume you have low testosterone if you’re having erection issues.
However, combined with other symptoms — like the ones listed above and below — erectile dysfunction could be a sign of a testosterone-related issue.
Studies show that low testosterone may affect 40 percent of men in infertile couples.
Testosterone is required in high concentrations within the testicles for sperm production. In addition, testosterone and some of its metabolites — like dihydrotestosterone (DHT) — support prostate and seminal vesicle function, two organs that are important for producing the fluid that carries sperm in the ejaculate.
It’s worth noting that testosterone is just one of several hormones that support male fertility, and not much is needed to create sperm. Some research suggests that while men with low T do have lower sperm counts and sperm quality than men with normal levels, these differences aren’t always statistically significant.
Put simply, having low T doesn’t necessarily mean you’re infertile.
It’s also very important to note that treating infertile men with testosterone makes infertility worse, not better. In fact, testosterone has been extensively studied as a form of male birth control.
Since the majority of testicular volume is comprised of the tubes that produce sperm, testicular shrinkage can be a sign of male infertility.
However, low testicular volume can also be a sign of testosterone deficiency.
That’s because testicular dysfunction tends to affect both things that the testicles do, making sperm and making testosterone, at the same time.
One study published in the journal Andrologia found an association between lower-than-normal levels of testosterone and reduced testicular volume.
Other research shows that hypogonadism is associated with a testicular volume of less than 15 mL and some degree of impaired sperm production.
Low testosterone has also been associated with poor quality sleep and sleep disturbances and disorders such as insomnia.
In one study of men aged 65 years and over, those with lower testosterone levels experienced reduced sleep efficiency, woke up more in the middle of the night, and had less time in slow-wave sleep or deep sleep. They were also more likely to have sleep apnea.
There also seems to be a bidirectional relationship between sleep and testosterone — as in, not getting enough sleep has been shown to alter testosterone levels. In a study of men who restricted their sleep to five hours per night, testosterone levels dropped around 10 to 15 percent as a result.
Low energy is one of the most common symptoms of testosterone deficiency. Affected men often find that they need to nap during the day just to stay functional.
Some men with low testosterone report feeling fatigued to the point that tiredness affects their quality of life and well-being. This symptom often coincides with concentration difficulties, depression, and diminished vitality. When treated with testosterone therapy, fatigue scores improve significantly.
Hot flashes, or flushes, are commonly associated with menopause in women. But they can also affect men with low testosterone due to hypothalamus dysfunction.
Remember: the hypothalamus is the part of the brain that signals the testicles to make testosterone. It also regulates body temperature.
Symptoms of hot flashes include sudden feelings of warmth across your face and chest, sweating, and redness.
As an anabolic (metabolism-related) hormone, testosterone plays a vital role in building and maintaining muscle mass. Studies show men with low testosterone levels experience muscle loss and decreased physical strength.
This loss of muscle mass, strength, and overall energy may also mean certain exercises, such as weightlifting and calisthenics, are more challenging to perform with low T.
Besides losing muscle mass, men with low testosterone may find their body composition changing and their body fat percentage increasing.
Like poor sleep and testosterone, research shows a bidirectional relationship between obesity and testosterone production.
Obesity and increased waist size have been shown to strongly predict low testosterone. And low testosterone contributes to an increase in body fat levels.
Hypogonadism is associated with numerous bodily functions that affect weight, including energy imbalances, reduced insulin sensitivity, impaired glucose control, and high lipid levels.
Increased fat from low testosterone levels can also increase your risk of high cholesterol, heart disease, and type 2 diabetes.
In addition to helping you grow muscle, testosterone is an essential hormone for bone health and maintenance. If you have low levels of testosterone, you may be more likely to suffer from decreased bone density. This could increase your risk of developing osteopenia, osteoporosis, and even fractures.
Not only does testosterone affect many physiological processes, but it can also have an impact on cognitive function and mood.
If you have low testosterone, you may have a higher risk of developing mood disorders like depression. This is attributed to how testosterone influences neurotransmitters in the brain.
Symptoms of low testosterone — like poor sleep and sexual dysfunction — may also exacerbate depressive symptoms.
Androgens, like testosterone, support optimal cognitive function — specifically, memory. They also protect neurons from inflammatory damage, shielding them against neurodegenerative diseases.
Low testosterone has often been linked to poor cognitive function, including brain fog and memory issues. This can hurt your workplace or academic performance.
Despite this, research hasn’t found a clear link between testosterone supplementation and an improvement in memory in men with low testosterone.
Testosterone is critical to creating red blood cells, which are essential for delivering oxygen to organs and removing carbon dioxide from the body.
Research shows that older men and women with low testosterone have lower red blood cell counts and an increased risk of developing anemia. Anemia can produce symptoms like fatigue, weakness, loss of appetite, headaches, and pale or yellowish skin.
We already mentioned how testosterone helps you grow facial and body hair in puberty. If you’re deficient in testosterone as an adult, your body hair may not grow to the same length or thickness as it previously did.
The hair on some parts of your body, such as your armpits or genitals, may start to thin. In addition to affecting body hair growth, low testosterone may also reduce the growth of your facial 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 might feel an enlargement 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.
From congenital conditions like Klinefelter syndrome to anabolic steroid use, there are many different health conditions and lifestyle habits that can affect testosterone production.
The causes of low testosterone depend on the type of hypogonadism you have: primary (involving the testicles) or secondary (involving the brain).
Common causes of primary hypogonadism include:
Klinefelter syndrome. Klinefelter’s syndrome occurs when a man is born with one or more extra X chromosomes, leading to a variety of impacts that include underdeveloped testicles, impaired testosterone production, and severe infertility. This disorder is incredibly common, affecting approximately one in 600 boys and men.
Undescended testicles. Also known as cryptorchidism, undescended testicles occur when one or both testicles fail to fully migrate into the scrotum during development. It can lead to low testosterone, male infertility, and a higher risk of certain cancers.
Testicular injuries. Injuries that affect the testes, such as physical trauma or complications due to poor blood supply, may result in low testosterone when they impact both testicles. Unilateral injuries on just one side typically don’t have a major impact if the unaffected testicle is healthy.
Cancer treatments. Chemotherapy and radiation therapy can cause permanent problems with both testosterone and sperm production.
Infections like mumps orchitis. Infections like mumps may temporarily or permanently affect testosterone by increasing inflammation in the testicles.
Common causes of secondary hypogonadism include:
Kallmann syndrome. This genetic condition refers to an abnormally developed hypothalamus, which can affect the secretion of pituitary hormones. Affected patients typically have an underdeveloped sense of smell because the nerves for smell also tend to be affected, and they don’t produce pituitary hormones because the signals from the hypothalamus are absent.
Pituitary disorders. Pituitary gland dysfunction can occur from tumors, infections, surgeries, or for other reasons. When the pituitary gland doesn’t produce LH and FSH, there’s no signaling from the brain to the testicles, and the testicles shut down. This results in male infertility and testosterone deficiency.
Being overweight or obese. Obesity is linked to a reduction in total testosterone, as well as reduced levels of LH and FSH. Poor pituitary production of LH is thought to be implicated in obesity-associated testosterone deficiency. One study revealed that altering a BMI from 30 to 25 kg/m2 could result in a 13 percent increase in testosterone.
Metabolic disorders. Certain metabolic disorders, such as hemochromatosis (extra iron buildup in the body), can cause or contribute to testosterone deficiency by affecting pituitary or hypothalamic function.
Alcohol abuse. Drinking heavily (and frequently) can have negative effects on sexual health, including reduced production of testosterone and other reproductive hormones.
Obstructive sleep apnea. Due to its effects on sleep duration and quality, obstructive sleep apnea may result in reduced pituitary hormone production, low testosterone production, and an increased risk of clinical testosterone deficiency.
HIV/AIDS. HIV and AIDS can impair testosterone production by impacting the hypothalamus, the pituitary gland, and the testes.
Medications. Using (or abusing) certain drugs like opioids may lower testosterone by altering pituitary or hypothalamic function.
Anabolic steroid use. Anabolic steroids used to increase muscle mass and strength can disrupt the natural function of the hypothalamic-pituitary-testicular hormonal axis. This can transiently or permanently disrupt natural testicular function by suppressing pituitary production of LH and FSH, potentially causing testicular atrophy (decreased testicular size), infertility, and severe testosterone deficiency.
Aging. Testosterone levels naturally decrease gradually over time. Research suggests that approximately 40 percent of men over 45 have clinically low testosterone levels.
Risk factors for developing hypogonadism include:
Advanced age
Obesity
HIV/AIDS
Sleep disorders
Type 2 diabetes
Post-chemotherapy and radiation
Chronic opioid use/abuse
Anabolic steroid use
Malnutrition
If you think you might have low testosterone, it’s best to bring this up with your healthcare provider or schedule an appointment with an endocrinologist or urologist.
At your appointment, your provider will ask about your medical and family health history and then perform a physical exam. They may also run a number of blood tests before diagnosing low testosterone.
These tests include:
A total testosterone test. This test measures your protein-bound and unbound (free) testosterone. It’s the most common type of test.
A free testosterone test. This test only measures your unbound testosterone, which is considered the most “active” or bioavailable form of testosterone. This test is less common, but some experts think it’s a more accurate indicator of low T.
LH and FSH test. If you do have low testosterone, your healthcare provider will test your LH and FSH levels to determine if the root of your low T is in the testicles or the brain (i.e. if you have primary or secondary hypogonadism). Primary hypogonadism is a form of testicular failure in which the testicles fail to produce enough testosterone despite strong stimulation from the pituitary gland. The hallmark of primary hypogonadism is low testosterone accompanied by increased FSH and LH.
Secondary hypogonadism, on the other hand, occurs because of inadequate hypothalamic or pituitary signaling to the testicles. It is identified by lab tests that show low testosterone accompanied by low to normal FSH and LH levels.
Remember, you may have low T if your total testosterone levels are below 300 ng/dL and you’re experiencing signs or symptoms of low testosterone.
The most popular treatment for low testosterone is testosterone replacement therapy (TRT), but it’s not the only one.
If you’re diagnosed with low T, your healthcare provider will likely suggest a range of treatment options.
Low testosterone treatments include:
Testosterone replacement therapy (TRT)
Medication to increase testosterone production
Medication for erectile dysfunction
Testosterone replacement therapy (TRT), or testosterone therapy, is a form of hormone replacement therapy for men.
This treatment uses synthetic testosterone to increase circulating testosterone levels and reduce low T symptoms. TRT comes in several forms, including skin patches, topical gels, oral capsules, implants, and injectable testosterone.
Testosterone replacement therapy has real benefits, including increased muscle mass and strength, improved sexual function, and enhanced mood.
But it may also cause side effects like skin irritation (particularly with gels), a high red blood cell count, acne, hair loss, and male infertility. TRT has also been linked by some reports to more serious issues, such as an increased risk of blood clots.
In some cases, testosterone replacement therapy can also worsen symptoms associated with low T, such as gynecomastia, sleep apnea, and testicular shrinkage.
Additionally, TRT may be unsafe if you have a history of prostate cancer or other forms of cancer affected by androgen levels. If you’ve previously received cancer treatment, it’s important to inform your healthcare provider before considering testosterone treatment.
Find out more about the benefits, risks, and potential side effects of TRT in our complete guide to testosterone replacement therapy.
An alternative to testosterone replacement, or sometimes used alongside testosterone, are medications that increase the production of testosterone.
These treatments can include selective estrogen receptor modulators like clomiphene (Clomid®), a derivative of clomiphene called enclomiphene, or aromatase inhibitors like anastrozole (Arimidex®). These drugs work by tricking the pituitary into increasing FSH and LH production in order to drive increased testicular function.
Another alternative to TRT is human chorionic gonadotropin (hCG), which functions like LH by signaling the Leydig cells in the testes to make more testosterone. A synthetic form of LH (Ovidrel) is also now available and functions in a similar way.
These medications allow users to avoid the negative impacts that TRT can have on sperm and even potentially improve fertility in some men. However, they only work if the testicles are healthy enough to respond well to increased hormonal stimulation. They usually are not effective in men with primary hypogonadism who have severe testicular failure.
Having low testosterone does not always lead to erectile dysfunction (ED), but it can in some men.
If you have erectile dysfunction and low testosterone, your healthcare provider might prescribe one of the following ED medications, either with or without treatment to raise your testosterone levels:
Sildenafil (generic Viagra®)
Avanafil (Stendra®), a newer medication
Hard Mints, a chewable ED medication containing the same active ingredients in Viagra® and Cialis®
These drugs make it easier to get and maintain an erection by relaxing the smooth muscle in the penis, which increases penile blood flow.
Our guide to the most common ED treatments explains more about how ED medications work.
Hypogonadism in males below 40 is becoming increasingly common, but there are several things you can do to support healthy testosterone production.
They include:
Exercising. Some research suggests that aerobic exercise may help increase testosterone by reducing fat and improving cardiorespiratory fitness.
Minimizing stress. Since prolonged or severe stress has been found to hinder testosterone production, finding better ways to manage stress supports hormonal health. This can include therapy or mindfulness practices.
Adjusting your diet. Improving your nutrition allows you to get the vitamins and minerals needed to synthesize testosterone. A nutritious diet can also help you maintain a healthy weight.
Prioritizing sleep. Getting proper rest supports bodily functions — including testosterone production.
Losing weight. If you’re overweight and not seeing results with exercise and diet alone, you may want to consider weight loss medication like glucagon-like peptide-1s (GLP-1s). Some research shows the medication is linked to improved testosterone levels in hypogonadal men.
Our guide to increasing your testosterone levels goes into more detail about how you can adjust your habits and lifestyle for better testosterone production.
If you think you have low testosterone, you’re not alone. And you’re not less of a man for struggling with your hormonal health. Reach out to a healthcare provider to get tested so you can get back to feeling like yourself again.