Low sperm count means a semen sample contains fewer sperm than the threshold needed for typical fertility. The current World Health Organization standard, updated in 2021, sets that lower limit at 16 million sperm per milliliter of semen. Falling below that number doesn’t mean you can’t conceive, but it does reduce the odds with each cycle.
How Sperm Count Is Measured
Sperm count is determined through a semen analysis, a lab test where a sample is examined under a microscope. The WHO recommends 2 to 7 days of abstinence from ejaculation before providing the sample, because ejaculating too recently or waiting too long can skew results. Most clinicians want to see at least two separate analyses before diagnosing a problem, since sperm counts naturally fluctuate from week to week.
The lab measures several things beyond raw count: how well the sperm move (motility), what percentage have a normal shape (morphology), and the total volume of the sample. A count below 16 million per milliliter is called oligozoospermia. Counts above that threshold but paired with poor motility or abnormal shape can still cause fertility problems, which is why doctors look at the full picture rather than a single number.
What It Feels Like (or Doesn’t)
Most people with low sperm count have no symptoms at all. The condition is typically discovered only after months of unsuccessfully trying to conceive. In some cases, an underlying cause produces noticeable signs: low sex drive, difficulty getting or maintaining an erection, pain or swelling near the testicle, a visible lump in the scrotum, or reduced facial and body hair. These aren’t symptoms of low count itself; they’re clues to whatever is driving the count down, whether that’s a hormonal imbalance, a varicocele, or another condition.
Common Causes
Varicocele
A varicocele is an enlarged vein inside the scrotum, similar to a varicose vein in the leg. It’s the most common identifiable cause of low sperm count. About 40% of men being evaluated for fertility problems have one. The leading theory is that the pooled blood raises the temperature around the testicle and increases oxidative stress, both of which interfere with sperm production. Not every varicocele causes infertility. An estimated 10% to 20% of men diagnosed with a varicocele have difficulty fathering a child.
Hormonal Imbalances
Sperm production depends on a carefully tuned hormonal chain. The brain releases signaling hormones that tell the testes to produce testosterone and to carry out spermatogenesis. Testosterone then feeds back to the brain to keep the system in balance. When any link in that chain is disrupted, sperm output drops. Conditions like hypothyroidism have been shown to impair sperm count, motility, and shape. The ratio of testosterone to estrogen also matters: one study found that infertile men had roughly half the testosterone-to-estrogen ratio of fertile men. Exogenous testosterone (such as from steroid use or testosterone replacement therapy) is a particularly common culprit, because flooding the body with outside testosterone signals the brain to shut down its own production, collapsing the hormonal cycle that drives sperm creation.
Lifestyle and Environmental Factors
Smoking is a well-established cause. Multiple large analyses confirm that cigarette smoking reduces sperm count and motility in a dose-dependent way, meaning the more you smoke, the greater the effect. The damage is reversible after quitting. Heat exposure from frequent hot tub or sauna use, prolonged laptop use on the lap, or occupations involving high temperatures can also suppress production, since the testes need to stay slightly cooler than core body temperature.
Environmental toxins are a growing concern. Researchers have documented a broad decline in male fertility over the past 50 years that can’t be fully explained by obesity, diet, or substance use alone. Industrial chemicals found in plastics, pesticides, and other common products are reproductively toxic and have been linked to lower sperm counts. Even radiofrequency energy from mobile phones has been associated with decreased sperm motility and viability in a meta-analysis of 10 studies, likely through heat generation and DNA damage at the cellular level.
What Low Count Means for Conception
Low sperm count reduces your chances of conceiving naturally, but it doesn’t eliminate them. In a study of 308 couples where the male partner had low counts, 22% achieved pregnancy when the concentration was above 2 million per milliliter, provided other semen qualities like motility and shape were adequate. Below 2 million per milliliter, the pregnancy rate dropped to 1.6%. So the severity of the count reduction matters enormously, and so does everything else about the sperm.
For couples pursuing assisted reproduction, different procedures have different thresholds. Intrauterine insemination (IUI) works best when the total number of motile sperm in the prepared sample exceeds about 10 million. Below 1 million motile sperm, IUI is generally not recommended. For counts that low, in vitro fertilization with a technique called ICSI, where a single sperm is injected directly into an egg, can bypass the numbers problem entirely. ICSI requires only one viable sperm per egg, making it an option even in cases of severe oligozoospermia.
Improving Sperm Count
New sperm take about 65 days to fully mature, so any change you make today won’t show up on a semen analysis for roughly two to three months. That timeline applies equally to quitting smoking, starting a supplement, losing weight, or treating a varicocele.
Several antioxidant supplements have shown the ability to improve sperm concentration in clinical trials. CoQ10 at 150 to 200 mg daily for about six months improved count, motility, and shape in multiple studies. Zinc supplementation has increased total normal sperm count in infertile men, with studies using doses ranging from 66 mg of elemental zinc up to 440 mg of zinc sulfate daily. A combination approach using L-carnitine (1,500 mg), CoQ10, zinc, vitamin C, vitamin E, folic acid, selenium, and vitamin B12 together for three months produced significant increases in concentration, motility, and normal morphology in one trial.
These supplements tend to work best when oxidative stress is part of the problem. They’re not a guaranteed fix, and they won’t overcome structural issues like a severe varicocele or a genetic condition. But for men with unexplained mild-to-moderate low counts, they represent a low-risk option worth trying during that initial two-to-three-month window before pursuing more intensive treatment.
When the Cause Is Treatable
If a hormonal imbalance is identified through blood work, targeted therapies can restore the signaling chain that drives sperm production. Medications that block estrogen’s feedback to the brain can raise the body’s own production of the hormones that stimulate the testes. For men with a condition where the brain simply doesn’t send those signals (hypogonadotropic hypogonadism), injectable hormones can substitute for the missing signals and restart sperm production.
Varicocele repair, either through a minor surgical procedure or a catheter-based approach, improves semen parameters in many men, though it can take three to six months to see the full effect. Stopping testosterone replacement therapy or anabolic steroids, if applicable, is often the single most impactful change, since these drugs directly suppress the hormonal axis responsible for making sperm. Recovery after stopping can take several months to over a year depending on how long and how heavily the drugs were used.