Male infertility can happen when the body makes too few sperm, sperm do not move or function well, or a blockage prevents sperm from reaching semen. Causes include varicocele (swollen veins around the testicles), infections, hormone or genetic conditions, past surgery, some medicines, cancer treatment, and exposures such as tobacco, heavy alcohol use, heat, or certain chemicals. In many cases, the exact cause is not found.
Male infertility refers to difficulty causing a pregnancy because of problems involving sperm production, sperm function, sperm transport, or sexual function. A low sperm count is one possible reason, but it is not the only one. Some men have fertility difficulties despite producing sperm in expected amounts, while others with lower sperm counts can still father a child. Identifying the possible cause helps healthcare professionals determine which evaluations or treatment options may be appropriate.
What is the difference between male infertility and low sperm count?
Low sperm count, also called oligospermia, means that semen contains fewer sperm than expected. Male infertility is a broader term that describes difficulty achieving pregnancy related to the male partner's reproductive function. Sperm may be present in adequate numbers but have problems with movement or shape, or a blockage may prevent sperm from entering the semen.
According to Mayo Clinic, male infertility can involve problems with sperm production, sperm movement and function, or the pathways that carry sperm. Several factors may occur together, and sometimes an evaluation cannot identify a clear cause.
Which medical conditions can cause low sperm count?
1. Varicocele
A varicocele is an enlargement of the veins inside the scrotum, the skin sac that holds the testicles. It is an important cause of male infertility because it can affect sperm production and quality. A varicocele does not always cause noticeable symptoms, and not everyone who has one experiences fertility problems. According to Cleveland Clinic, varicoceles are among the common conditions associated with low sperm count. A healthcare professional can assess whether a varicocele may be relevant to an individual's fertility.
2. Infections affecting the reproductive system
Some infections can interfere with sperm production, affect sperm health, or cause scarring that blocks the passage of sperm. Inflammation of the testicles, known as orchitis, and inflammation of the epididymis, the coiled tube behind each testicle, may affect fertility. Certain sexually transmitted infections, including gonorrhea, can also damage parts of the reproductive tract if complications develop. The NHS identifies reproductive infections and testicular damage among the possible causes of male infertility. The effects depend on the infection and whether lasting damage has occurred.
3. Hormone imbalances
Sperm production depends on signals from the brain and hormones produced by the reproductive system. The hypothalamus and pituitary gland in the brain help regulate testicular function, while testosterone and other hormones support sperm production. Conditions affecting these systems can interfere with the development of sperm. Low testosterone may occur for several reasons, including disorders involving the testicles or hormone-regulating glands, but a testosterone result alone does not establish whether sperm production is normal or impaired.
4. Genetic and developmental conditions
Some inherited conditions affect how the testicles or reproductive ducts develop and function. Klinefelter syndrome, a chromosome condition, can interfere with sperm production. Certain forms of cystic fibrosis are associated with the absence or abnormal development of the vas deferens, the tubes that carry sperm toward the urethra. Undescended testicles, which occur when one or both testicles do not move into the scrotum before birth, can also affect future fertility. The impact varies according to the condition and the extent of reproductive system involvement.
5. Blockages and previous reproductive surgery
Sperm must travel from the testicles through a network of small ducts before leaving the body during ejaculation. Blockages caused by infection, injury, congenital differences, or surgery can prevent sperm from reaching the semen even when the testicles continue producing them. A vasectomy intentionally blocks the tubes that carry sperm. Some procedures involving the testicles, prostate, pelvis, or urinary tract may also affect sperm transport or ejaculation. When a blockage is suspected, the medical evaluation helps distinguish a transport problem from reduced sperm production.
Can medicines and medical treatments affect sperm production?
Yes. Certain medicines and medical treatments can reduce sperm production or interfere with other aspects of fertility. The effects depend on the substance, dose, duration of use, and the person's health. Testosterone replacement therapy and anabolic steroids are especially important to discuss with a healthcare professional because testosterone taken from outside the body can suppress the hormonal signals needed for sperm production.
According to Mayo Clinic's information on low sperm count, some prescription medicines, previous surgeries, and cancer treatments may affect male fertility. Chemotherapy and radiation can damage sperm-producing cells, with effects that vary according to the treatment and exposure. Some medicines used for other conditions may also affect reproductive function. Anyone concerned about a medication's effect on fertility should review it with the prescribing clinician rather than stopping it independently.
Which lifestyle and environmental factors are linked to low sperm count?
Daily habits and workplace exposures may contribute to changes in sperm production or quality. Their effects are not the same for everyone, and the presence of a risk factor does not prove that it is responsible for fertility difficulties.
- Smoking and tobacco exposure: Tobacco use is associated with reduced sperm quality and may contribute to lower sperm counts.
- Heavy or prolonged alcohol use: Excessive alcohol consumption may affect hormone levels, sexual function, and sperm production.
- Recreational drugs and anabolic steroids: Cocaine, marijuana, and drugs used to increase muscle size may negatively affect sperm quantity or function. Anabolic steroids can suppress sperm production.
- Higher body weight: Obesity may affect fertility through changes in hormone function and sperm health.
- Excessive heat exposure: The testicles normally remain cooler than the body's core temperature. Certain sustained or repeated heat exposures may temporarily affect sperm production, although the effect depends on the exposure.
- Workplace chemicals and heavy metals: Some pesticides, industrial chemicals, lead, and other toxic substances may affect reproductive function, particularly with relevant exposure.
- Radiation: Exposure to radiation, including some cancer treatments, can impair sperm production. The extent and duration of the effect depend on the type and amount of exposure.
These factors are worth discussing during a fertility assessment, particularly when exposure is ongoing. Reducing avoidable risks can support reproductive health, but lifestyle changes alone may not correct a medical, genetic, hormonal, or structural cause.
Why is the cause of male infertility sometimes unknown?
Some men have an abnormal semen analysis even though their medical history, physical examination, and other investigations do not reveal a clear explanation. This is sometimes described as unexplained male infertility. Several subtle factors may affect sperm development, movement, or function, and current tests cannot identify every possible cause.
Sperm production may also change over time. A recent illness, some medications, incomplete sample collection, or differences in testing conditions may influence a semen analysis result. An unexpected result therefore needs to be considered in context rather than treated as a complete explanation for difficulty conceiving.
How do healthcare professionals investigate possible causes?
An evaluation generally begins with a review of medical history, sexual and reproductive health, medications, previous operations, illnesses, and possible environmental exposures. A physical examination may help identify findings involving the testicles or reproductive system. The evaluation may also consider how long the couple has been trying to conceive and whether either partner has relevant medical factors.
A semen analysis is a key test. It assesses features such as sperm concentration, movement, shape, and semen volume. MedlinePlus explains that semen analysis results must be interpreted in context and that abnormal findings do not automatically mean a man cannot father a child. Depending on the initial findings, a clinician may recommend repeat semen testing, hormone blood tests, genetic tests, or imaging to investigate a suspected cause.
Both partners may need evaluation because fertility difficulties can involve male factors, female factors, a combination of factors, or no identifiable cause. The results help guide decisions about whether further investigation, treatment of an underlying problem, or fertility assistance may be appropriate.
When should you seek a fertility evaluation?
Consider arranging an evaluation if pregnancy has not occurred after 12 months of regular sexual intercourse without contraception. An earlier assessment is generally appropriate when the female partner is older than 35, often after six months of trying. Seek advice sooner if there is a known reproductive condition, a history of undescended testicles, previous chemotherapy or radiation, testicular injury or surgery, or persistent problems with erections or ejaculation.
Testicular pain, swelling, or a new lump also warrants medical assessment, whether or not you are trying to conceive. A clinician can decide which findings require prompt investigation and whether referral to a urologist or fertility specialist would be helpful.
Can male infertility or low sperm count be improved?
In some cases, fertility improves when an underlying cause can be treated. Depending on the findings, care may involve treating an infection, addressing a hormone disorder, reviewing a medicine that affects sperm production, or considering a procedure for a relevant varicocele or blockage. When sperm production cannot be restored or the cause remains unexplained, assisted reproductive options may still offer a path to pregnancy.
There is no single treatment that works for every cause of male infertility. The appropriate approach depends on the evaluation, the couple's reproductive goals, and the health factors involved. Men concerned about fertility should discuss treatment options with a qualified healthcare professional before starting hormone products, supplements, or other remedies.