Male infertility is a condition that affects millions of men worldwide, preventing them from helping their partner conceive despite regular, unprotected intercourse. While conversations about starting a family often center on women’s reproductive health, men play an equally important role in the conception process. Understanding the causes, symptoms, and available options can help couples navigate this challenging journey together.

Epidemiology

Male infertility is far more common than many people realize. It affects approximately 10 to 15 percent of males in the United States who are actively trying to conceive with their partners. Globally, infertility touches the lives of at least 180 million couples worldwide, and in roughly 186 million people affected by infertility, the male partner is responsible for about half of all cases.^[2][3]

When couples struggle to achieve pregnancy, the male factor is solely responsible in about 20 percent of cases. However, men contribute to infertility in another 30 to 40 percent of all situations, meaning that overall, male factors substantially contribute to about 50 percent of all infertility cases. Nearly one in seven couples experiences infertility, defined as the inability to conceive even after a year or longer of frequent, unprotected sexual intercourse.^[1][3]

It’s important to understand that conception is not an easy process, even for healthy couples. Humans are considered a species with low reproductive capacity. A fertile and young couple has only a 20 to 25 percent chance of conceiving each month they have unprotected intercourse. This means that even under ideal conditions, becoming pregnant takes time and patience.^[2][15]

Age plays a role in male fertility as well. Men who are 40 years or older tend to have higher chances of experiencing fertility issues. Additionally, men with a body mass index greater than 25, indicating overweight or obesity, face increased risk of infertility problems.^[2]

Causes

Male infertility stems from a wide range of biological and environmental factors. Understanding what causes these problems helps men and their healthcare providers develop appropriate treatment plans. The most common cause relates to issues with sperm themselves, including problems with how sperm are produced, how they function, or how they are delivered.^[1]

Sperm problems represent the primary cause of male infertility. These include malformed sperm that don’t have the typical shape needed to fertilize an egg, low sperm count (a condition called oligospermia), and the complete absence of sperm in semen (called azoospermia). Healthy conception requires around 20 million sperm per milliliter to be present in the ejaculate, with enough mobility and strength to swim the journey to the fallopian tube where fertilization takes place.^[2][8]

Physical blockages can prevent sperm from reaching their destination. These obstructions in the tubes that carry sperm account for around one in three cases of male infertility. The sperm journey begins in the testicles, then travels through small tubes called the epididymis where sperm mature over 2 to 10 days. They then exit into a larger tube called the vas deferens, which empties into the ejaculatory duct where sperm mix with seminal fluid. Blockages or absences of these tubes may be present since birth (congenital) or result from vasectomy or injury.^[8][15]

Genetic disorders can interfere with fertility. Conditions such as Klinefelter syndrome and myotonic dystrophy are known to affect sperm production and quality. Some men with sperm problems have tiny fragments of the male chromosome missing, which can cause significant reproductive issues.^[2][8]

Several medical conditions contribute to male infertility. Diabetes, certain autoimmune diseases that attack sperm, and cystic fibrosis all impact reproductive health. Infections, including epididymitis (inflammation of the epididymis), orchitis (inflammation of the testicle), and sexually transmitted infections like gonorrhea or HIV, can damage the reproductive system and affect sperm quality.^[2]

A condition called varicocele, which involves swollen veins in the testicles, is another common cause. When these veins become enlarged, they trap blood around the testicle, potentially damaging sperm through excess heat and other mechanisms. Physical injury to the testicle, undescended testicles, and surgery on the testis or nearby areas such as hernia repairs can all harm fertility.^[2][5]

Cancer treatments pose serious risks to male fertility. Chemotherapy, radiation therapy, or surgical removal of the testicles can severely impact or eliminate sperm production. Hormonal disorders affecting the hypothalamus or pituitary glands, which control hormone production, can disrupt the delicate balance needed for healthy sperm creation.^[2]

Risk Factors

Numerous medical conditions and lifestyle habits increase a man’s risk of experiencing fertility problems. Being aware of these risk factors allows men to take preventive steps and seek help when needed. Any male can experience infertility, but certain circumstances make it more likely.^[2]

Medical conditions that put patients in high-risk groups include endocrine disorders or hormone imbalances, physical injury to the testicle, undescended testicles, surgery on the testis or nearby areas like hernia repairs, and exposure to toxic chemicals including chemotherapy or radiation. Physical blockages in the sperm delivery routes and the use of testosterone or other anabolic steroids significantly impact fertility.^[5]

What’s good for general health is also good for sperm health. Several lifestyle habits may put a man at higher risk for infertility. Smoking represents a major risk factor, as tobacco use damages sperm and limits the chances of survival for embryos that are created. The American Society of Reproductive Medicine states that the chances of early pregnancy loss increase if the father smokes.^[5][19]

Excessive alcohol consumption can lower testosterone levels and cause erectile dysfunction. Men who regularly drink high amounts of alcohol can have abnormal sperm parameters, though low to moderate amounts (two drinks per day or less for men) don’t appear to have these same effects.^[5][19]

Exposure to heat negatively affects sperm production. Sperm quality depends on maintaining the right temperature, about two degrees cooler than body temperature. Spending too much time in saunas or hot tubs can lead to lower sperm counts. Patients are also warned against working with laptop computers on their laps, wearing tight underwear that keeps the testicles too close to the body, and exposing the genital area to other sources of excess heat.^[5][19]

Poor diet plays a role in fertility. Recent studies show that diets high in saturated fats and low in nutrients can decrease sperm production. Minimizing or avoiding ultra-processed foods and sugar is helpful for maintaining reproductive health.^[5][19]

Stress affects the body as a whole and can contribute to male fertility problems. Just as unmanaged stress wreaks havoc on other body systems, it impacts reproductive function. Drugs ranging from marijuana to anabolic steroids to the entire family of opiates are linked to lower sperm counts and reduced fertility.^[5]

Environmental factors also matter. Lowering exposure to chemicals might improve fertility. Pesticides, heavy metals, bisphenol A (BPA), and other toxins may harm sperm and male fertility. Men can reduce chemical exposure by avoiding harsh cleaning chemicals, fragrances and air fresheners, outdoor exercise during rush hour when pollution is highest, paints and solvents, pesticides and herbicides, and products containing BPA such as some plastic water bottles and canned foods.^[19]

Symptoms

The main sign of male infertility is the inability to conceive a child with a partner after trying for a year or longer. In many cases, there are no other obvious signs or symptoms that something is wrong. However, certain warning signs may indicate an underlying problem that requires medical attention.^[1]

Some men experience problems with sexual function. This includes difficulty with ejaculation, such as ejaculating very small volumes of fluid or no ejaculation at all. Reduced sexual desire or difficulty maintaining an erection (called erectile dysfunction) can also signal fertility issues. These problems may point to hormonal imbalances or other conditions affecting reproductive health.^[1][9]

Physical symptoms in the testicle area warrant attention. Pain, swelling, or a lump in the testicle area should always be evaluated by a doctor. These signs could indicate conditions like varicocele, infections, or in rare cases, testicular cancer.^[1][9]

Recurrent respiratory infections and an inability to smell may seem unrelated to fertility, but they can indicate underlying conditions affecting reproduction. Signs of hormonal imbalance include abnormal breast growth (called gynecomastia) and decreased facial or body hair. These symptoms suggest that hormone levels may not be in the proper balance for healthy sperm production.^[1]

A lower-than-normal sperm count serves as a clear indicator of fertility problems. Normal counts should have at least 15 million sperm per milliliter of semen or a total sperm count of at least 39 million per ejaculate. Men won’t know their sperm count without testing, which is why evaluation becomes important when conception doesn’t occur within expected timeframes.^[1][9]

Male infertility can be associated with low testosterone production from the testicles. When this occurs, symptoms such as tiredness, impotence, depression, weight gain, and apathy may appear. These symptoms affect overall quality of life and signal the need to consult with a urologist who specializes in male infertility or a reproductive endocrinologist.^[2]

Beyond physical symptoms, male infertility leads to significant psychological and emotional effects. The primary experience of being unable to have a biological child can trigger intense feelings of depression, loss, grief, inadequacy, and failure. Some men believe that their masculinity is wrapped up in their ability to give their partner a child, and feeling they have lost that ability produces strong negative emotions. Men tend to be less likely than women to open up about these feelings, which can make the experience even more isolating.^[2][17]

Prevention

While not all causes of male infertility can be prevented, many lifestyle changes and health practices can help protect and improve fertility. Taking proactive steps supports overall reproductive health and increases the chances of successful conception.

Managing chronic health conditions represents one of the most important preventive measures. Almost any health condition can affect a man’s reproductive health, even conditions that seem unrelated to fertility. Diseases like high blood pressure and diabetes affect semen quality, sperm count, and sperm motility (sperm’s ability to swim). Having one of these conditions doesn’t mean conception is impossible, but proper healthcare management is essential. Healthcare providers may recommend lifestyle changes, medications, or other therapies to get conditions under good control, which can make a big difference in fertility.^[19]

Preventing and treating sexually transmitted infections is crucial. Using condoms or other protection helps prevent STIs. Getting regular STI testing and screening allows for early treatment, which helps avoid the scarring and blockages that untreated infections can cause in the reproductive tract.^[19]

Quitting smoking provides significant benefits. Smoking negatively affects almost every system in the body, including the ability to make healthy sperm. Quitting can boost chances of conceiving and improve overall health. Studies have found that men who quit smoking saw improvements in their sperm count, quality, and motility.^[19]

Limiting alcohol intake to moderate amounts helps protect fertility. For men, moderate drinking means two drinks per day or less. Regularly drinking more than this can lower testosterone levels and sperm production.^[19]

Avoiding excess heat near the genital area supports healthy sperm production. Men should avoid placing laptops or other electronic devices on their laps, stay away from hot environments like saunas, hot tubs, and hot yoga, and avoid tight underwear that keeps the testicles too close to the body. The testicles naturally drop slightly away from the body when things get too warm to maintain the proper temperature for sperm production.^[19]

Minimizing exposure to chemicals protects reproductive health. While avoiding all chemicals isn’t possible, lowering exposure can help. This means limiting contact with pesticides, heavy metals, BPA, fragrances, harsh cleaning chemicals, paints and solvents, and choosing BPA-free products.^[19]

Eating a nutritious diet supports fertility. A diet full of whole foods, including plenty of fruits, vegetables, nuts, and seeds, can improve fertility. Foods rich in antioxidants appear to have positive effects on male fertility. Eating more dark vegetables, fruits, and high-protein foods, and increasing intake of polyunsaturated fats from sources such as tree nuts, helps support sperm health.^[19][21]

Maintaining a healthy weight matters for fertility. Losing excess weight helps because obesity causes decreased testosterone. Additionally, extra weight can increase the temperature of the scrotum and decrease sperm production. Exercising for 30 minutes or more each day improves metabolism, which means better sperm production.^[21]

Getting adequate sleep supports reproductive health. Six or more hours of sleep each night helps reduce stress and allows the pituitary gland, which is responsible for sperm production, to recharge properly.^[21]

Pathophysiology

Understanding how male infertility develops involves looking at the normal process of sperm production and delivery, and recognizing what goes wrong when this process is disrupted. Conception is a complicated process that depends on many factors working together properly in both male and female reproductive systems.^[2]

In the male body, sperm production begins in the testicles. Around 80 percent of a man’s testicles are dedicated to sperm production. After sperm are made, they spend 2 to 10 days passing through a series of small tubes called the epididymis, where they mature and gain the ability to move and fertilize an egg. From there, sperm exit into a larger tube called the vas deferens.^[8][21]

The vas deferens empties sperm into the ejaculatory duct, where they mix with seminal fluid from the seminal vesicles and the prostate gland. During ejaculation, muscular contractions force the semen into the urethra and out of the penis. This entire pathway must be open and functioning properly for sperm to reach their destination.^[15]

Healthy sperm depend on three main characteristics: quantity, movement, and shape. Ideally, semen in a single ejaculation should contain at least 15 million sperm per milliliter. Having fewer than this lowers the chances of pregnancy because there are fewer sperm available to fertilize an egg. For movement, also called motility, at least 40 percent of sperm need to be able to move to achieve pregnancy. Sperm must be able to swim easily through the cervix, uterus, and fallopian tubes to reach and fertilize an egg. Although pregnancy can happen with lower levels of sperm movement, it’s much less common.^[18]

The typical shape of sperm matters too. Normal sperm have oval heads and long tails that work together to help them move. This is called morphology. In general, sperm shape isn’t as important to fertility as quantity or movement, but having more normally shaped sperm increases the chances that at least one will be able to successfully fertilize an egg.^[18]

When blockages occur in the reproductive tract, sperm cannot exit the body even if they are being produced normally. These blockages may be present since birth, or they can result from infections that cause scarring, previous vasectomy, or physical injury. The sperm become trapped and unable to reach the ejaculate.^[8]

Problems with sperm quality often have genetic causes. Research has found that tiny fragments of the male chromosome may be missing in some men with sperm problems. This genetic damage can lead to absent sperm, very low sperm counts, poor sperm movement, or abnormal sperm shape.^[8]

Varicocele affects sperm production through a different mechanism. When veins in the scrotum that drain blood from the testis become abnormally dilated and large, they trap blood around the testicle. This causes the testicle to overheat, which damages sperm production. The excess heat affects both the number and shape of sperm that are produced.^[9]

Hormonal imbalances disrupt the signals needed for normal sperm production. The hypothalamus and pituitary glands in the brain control the release of hormones that tell the testicles to make sperm. When these glands don’t function properly, testosterone production drops and sperm production suffers. Sometimes low testosterone production from the testicles creates a feedback loop that further reduces fertility.^[2]

Infections cause inflammation and damage to the reproductive organs. Epididymitis inflames the tubes where sperm mature, while orchitis inflames the testicles themselves. Sexually transmitted infections can create scarring and blockages throughout the reproductive tract. Even after infections are treated, the damage they cause may persist and continue to affect fertility.^[2]

For pregnancy to occur and continue successfully, multiple steps must work perfectly. The male must produce healthy sperm, the female must produce a healthy egg, the fallopian tubes must be unblocked to allow sperm to reach the egg, the sperm must be able to fertilize the egg when they meet, and the fertilized egg (embryo) must be able to implant in the uterus. The embryo must be healthy and the female’s hormonal environment adequate for the embryo to develop to full term. Infertility can happen if something affects just one of these factors.^[2]