Low Sperm Count: Common Causes and What You Can Do

Low sperm count is one of those topics that doesn’t come up in casual conversation, but it’s a common piece of the fertility picture and, perhaps less widely known, can sometimes be an early signal of a broader health issue worth addressing. Understanding the common causes of low sperm count — from medical conditions to lifestyle factors to things in your environment — can help you know what’s worth bringing up with a doctor and what steps might actually make a difference.

What Does a Low Sperm Count Actually Mean?

A low sperm count, medically called oligospermia, means there’s less sperm in a semen sample than is typical — specifically, according to Mayo Clinic, fewer than 15 million sperm per milliliter. A complete absence of sperm is a related but distinct condition called azoospermia. Having a lower sperm count doesn’t mean pregnancy is impossible, but it does reduce the odds that a sperm will successfully reach and fertilize an egg, which is why it’s one of the factors doctors look at when a couple is having trouble conceiving. It’s worth noting that sperm count is only one part of the fertility picture — sperm movement (motility) and shape (morphology) matter too, and a semen analysis typically evaluates all three together rather than count alone.

The Main Symptom: Difficulty Conceiving

For many people, the only noticeable sign of a low sperm count is trouble starting a pregnancy with a partner after a reasonable period of trying — there often aren’t other obvious symptoms. In some cases, though, an underlying condition causing the low sperm count brings its own signs along with it: reduced sex drive, difficulty getting or maintaining an erection firm enough for sex, pain, swelling, or a noticeable lump in the testicle area, or reduced facial or body hair, which can point to a hormone or chromosome-related condition. Mayo Clinic recommends seeing a healthcare professional if you and your partner haven’t conceived after a year of regular, unprotected sex — which is the clinical definition of infertility — or sooner if you notice any of the symptoms above, have a history of testicle, prostate, or sexual problems, or have had surgery involving the groin, testicles, penis, or scrotum.

Medical Causes

Several health conditions are directly linked to low sperm count. Varicocele — a swelling of the veins that drain the testicle, similar to varicose veins — is described by Mayo Clinic as a common cause of male infertility, and it’s one of the more treatable ones: surgery to correct a varicocele can improve sperm count, movement, and shape in many cases. Infections, including sexually transmitted infections like gonorrhea, as well as viral or bacterial infections that cause inflammation of the testicles or the epididymis (the coiled tube behind each testicle), can impact sperm production, sometimes causing lasting damage if repeated or untreated. Problems with ejaculation, including a condition called retrograde ejaculation (where semen enters the bladder instead of exiting normally), can be caused by diabetes, spinal injuries, or certain surgeries, and some ejaculation-related medications, like alpha blockers used for blood pressure or enlarged prostate, can contribute as well. Hormone imbalances involving the hypothalamus, pituitary gland, thyroid, or the testicles themselves can disrupt the signals needed for normal sperm production, and tumors, undescended testicles, genetic conditions such as Klinefelter syndrome, and blockages in the tubes that carry sperm are all recognized medical causes.

Medications and Past Surgeries

Certain medications can reduce sperm production as a side effect, including some treatments for arthritis, depression, anxiety, low testosterone, digestive conditions, infections, high blood pressure, and cancer. This is one of the more overlooked causes, since the connection to fertility isn’t always obvious from a medication’s main purpose, which is why it’s worth reviewing your full medication list with a doctor if low sperm count is a concern. Past surgeries can also play a role: procedures like vasectomy, inguinal hernia repair, surgeries involving the scrotum, testicles, or prostate, and major abdominal surgery for cancer treatment can all affect whether sperm make it into the semen. Many of these are reversible or workable, whether through surgery to correct a blockage or through techniques that retrieve sperm directly from the testicles for use in fertility treatment.

Environmental and Lifestyle Causes

A number of everyday exposures and habits are linked to lower sperm count. Mayo Clinic lists industrial chemicals such as pesticides, insecticides, and organic solvents, along with heavy metal exposure like lead, as potential contributors with prolonged contact. Radiation exposure can reduce sperm production, sometimes for years afterward, and at high doses, the effect can be permanent. Overheating the scrotum — from frequent hot tub or sauna use, tight-fitting underwear, or jobs involving prolonged sitting in heat — may also affect sperm count and function, since the testicles are positioned outside the body specifically because sperm production is sensitive to temperature. On the lifestyle side, smoking tobacco, heavy or regular alcohol use, and the use of anabolic steroids, cocaine, or marijuana are all associated with reduced sperm count and quality. Obesity may affect sperm directly or indirectly through hormone changes, and chronic emotional stress, including the stress of fertility struggles themselves, has also been linked to reduced semen quality, creating a frustrating cycle for some couples.

Low Sperm Count Is Only Part of the Fertility Picture

It’s easy to focus on the number itself, but fertility specialists look at sperm health more broadly than count alone. Motility, or how well sperm move, matters because sperm need to travel through the reproductive tract and penetrate an egg to achieve fertilization — a normal count with poor motility can still make conceiving difficult. Morphology, the shape and structure of individual sperm, is another factor evaluated on a standard semen analysis, since irregularly shaped sperm are less likely to fertilize an egg successfully even when the overall count looks adequate. This is part of why a semen analysis report includes several numbers rather than a single count, and why two people with technically “low” counts can have very different fertility outlooks depending on how the rest of the sample looks. It’s also a reason not to self-diagnose from a single number without the full context a doctor can provide.

Why Sperm Count Results Can Vary

It’s worth knowing that a single low result doesn’t necessarily mean a persistent problem. Mayo Clinic notes that sperm count can appear artificially low due to testing issues — for example, if the sample is collected too soon after a previous ejaculation, during or shortly after an illness or significant stress, or if part of the sample is lost during collection. Because of this natural variability, fertility evaluations typically rely on results from a few samples collected over time rather than a single test, which gives a more accurate and reliable picture of actual sperm production.

Risk Factors to Be Aware Of

Certain factors raise the likelihood of having or developing a low sperm count. Lifestyle-related risk factors include smoking, drinking alcohol regularly, and using recreational drugs. Health-related risk factors include being overweight, having ongoing high stress levels, a history of testicle trauma, past or current infections, and being born with — or having a blood relative with — a fertility disorder. A history of undescended testicles is also a recognized risk factor. On the treatment side, cancer treatments like radiation, certain medications, and procedures like vasectomy or major pelvic surgery raise the risk as well. Being aware of these doesn’t mean a low sperm count is inevitable, but it can help explain why a sperm count changed, and it points toward which lifestyle adjustments might genuinely help.

What You Can Do

Mayo Clinic’s prevention guidance centers on reducing exposure to known risk factors where possible: avoiding smoking, limiting or avoiding alcohol, staying away from illicit drug use, maintaining a healthy weight, avoiding prolonged overheating of the scrotum, managing stress, and minimizing exposure to pesticides, heavy metals, and other environmental toxins where you reasonably can. It’s also worth reviewing your current medications with a doctor to see if any are known to affect fertility, since a simple substitution is sometimes possible. None of these steps guarantee a higher sperm count, since many cases have a cause that isn’t fully understood or isn’t something lifestyle changes alone can fix, but they represent the factors genuinely within your control.

When to See a Doctor

See a healthcare professional if you and your partner haven’t been able to conceive after a year of regular, unprotected sex, or sooner if you notice symptoms like low sex drive, erectile difficulty, pain or swelling in the testicle area, or if you have a relevant medical or surgical history. A doctor can order a semen analysis and, depending on the results, additional hormone testing or imaging to help pinpoint a cause. Many causes of low sperm count are treatable or workable with the right approach, so an evaluation is often more reassuring and actionable than people expect going in.

Frequently Asked Questions

Can low sperm count be reversed?

It depends on the cause. Conditions like varicocele can often be surgically corrected with improvement in sperm count and quality, and lifestyle-related causes like smoking, alcohol use, or being overweight can improve with changes to those habits. Other causes, particularly genetic ones, generally can’t be reversed, though fertility treatments may still be an option.

What is considered a low sperm count?

According to Mayo Clinic, a sperm count is considered low if it’s fewer than 15 million sperm per milliliter of semen. A complete absence of sperm in the semen is a related but separate condition called azoospermia.

Does low testosterone cause low sperm count?

Hormone imbalances, including those involving testosterone and the hormones that regulate it from the brain, can interfere with sperm production. The relationship is complex, since testosterone replacement therapy itself can actually lower sperm count in some cases, which is worth discussing with a doctor if fertility is a goal.

Can stress alone cause a low sperm count?

Long-term emotional stress has been linked to reduced semen quality, though it’s typically one factor among several rather than a sole cause. Managing stress is part of Mayo Clinic’s general guidance for supporting sperm health, alongside other lifestyle factors.

How is low sperm count diagnosed?

It’s diagnosed through a semen analysis, which measures sperm count along with movement and shape. Because results can vary based on timing and recent illness or stress, doctors typically base conclusions on more than one sample collected over time rather than a single test.

This article is for general educational purposes and isn’t a substitute for personalized medical advice. If you’re concerned about fertility or sperm count, talk to your doctor about an evaluation tailored to your situation.

Low sperm count has many possible causes, ranging from easily treatable conditions like varicocele to lifestyle factors you can address on your own, and in a meaningful share of cases, no clear cause is ever found. Rather than guessing at the reason, a straightforward evaluation with a doctor — starting with a semen analysis — is usually the most direct way to understand what’s going on and what options might help.