Low sperm count, clinically called oligospermia, means a semen sample contains fewer than 15 million sperm per milliliter. A typical sample holds 15 million or more per milliliter, so anything below that threshold reduces the odds of conception. About 27 to 28% of assisted reproduction cycles in North and South America involve a male factor diagnosis, and the number is even higher in some parts of the world.
How It’s Diagnosed
A semen analysis is the standard test. You’ll be asked to avoid ejaculation for two to three days beforehand, but not longer than five days, since sperm quality can decline after that. The sample needs to reach the lab within 30 minutes and be examined within two hours of collection. Most providers will want at least two separate analyses, spaced a few weeks apart, because sperm counts naturally fluctuate.
The lab measures three main things: concentration (how many sperm per milliliter), motility (what percentage are swimming effectively), and morphology (what percentage have a normal shape). Low sperm count often appears alongside poor motility or abnormal shape, but it can also show up on its own.
Symptoms You Might Notice
The primary sign is difficulty conceiving. Most people with a low count don’t have any outward symptoms at all. When symptoms do appear, they usually point to an underlying hormonal or structural problem: low sex drive, difficulty getting or maintaining an erection, pain or swelling in the testicle area, or reduced facial and body hair. A noticeable lump near the testicle can signal a varicocele, which is one of the most common treatable causes.
Why Sperm Count Drops
Varicoceles
A varicocele is an enlarged vein in the scrotum, similar to a varicose vein in the leg. The scrotum normally keeps the testes two to four degrees Celsius cooler than core body temperature, which is essential for sperm production. When a varicocele forms, blood pools and stagnates, raising scrotal temperature. Research shows that a sustained temperature increase of just 1 to 1.5°C is enough to trigger sperm cell death, shrink testicular tissue, and reduce both sperm output and sperm quality. Men with varicoceles also show higher rates of abnormally shaped sperm and genetic errors in sperm cells compared to controls. Varicoceles are found in roughly 40% of men evaluated for infertility, making them the single most common identifiable cause.
Hormonal Problems
Sperm production depends on a chain of signals that starts in the brain. The hypothalamus releases a hormone that tells the pituitary gland to produce two key signaling hormones. One of those stimulates sperm production directly, while the other triggers testosterone release from the testes. If any link in that chain breaks, sperm output falls.
Pituitary tumors, even noncancerous ones, can suppress these signals. So can iron overload (hemochromatosis), which damages the pituitary gland or the testes themselves. Chronic infections like HIV can affect all three parts of the chain. Radiation or surgery near the brain, even for unrelated conditions, sometimes disrupts pituitary function as a side effect.
Environmental and Chemical Exposures
Rising infertility rates have been linked to greater exposure to chemicals that interfere with hormone signaling. The most studied culprits are phthalates, bisphenol A (BPA), pesticides, and heavy metals like cadmium and lead.
Phthalates, commonly found in plastics and personal care products, suppress testosterone production. Men in the highest exposure group have 12 to 15% lower testosterone levels and significantly reduced sperm motility compared to men with low exposure. BPA, found in food packaging and receipt paper, has a similar effect, binding to estrogen receptors in the testes and interfering with sperm maturation. Both chemicals increase oxidative stress inside the reproductive tract. Men with high BPA or phthalate exposure have 25 to 30% higher levels of damaging reactive molecules in their semen, which directly harms sperm DNA.
Other Common Causes
Infections of the reproductive tract, including sexually transmitted infections, can scar the tubes that carry sperm or damage testicular tissue. Certain medications, particularly testosterone replacement therapy (which paradoxically shuts down the body’s own sperm production), anabolic steroids, and some chemotherapy drugs, are well-known causes. Undescended testicles, even if corrected in childhood, carry a higher lifetime risk of reduced sperm production. Obesity also plays a role: excess body fat raises scrotal temperature and disrupts hormone balance in ways that mirror the effects of a varicocele.
Treatment Options
Treatment depends entirely on the cause. Varicocele repair, either through minor surgery or a catheter-based procedure, improves sperm counts in a significant portion of men. The goal is to restore normal blood flow and let scrotal temperature drop back to its optimal range.
For hormonal causes, medications can stimulate the brain’s signaling pathway to restart sperm production. One commonly used approach works by blocking estrogen receptors in the brain, which tricks the pituitary into releasing more of the hormones that drive both testosterone and sperm output. Treatment typically starts at a low dose and is adjusted over several months. Sperm production is a slow process, taking roughly 72 days from start to finish, so improvements in semen analysis results usually don’t appear for at least three months.
When an infection is the cause, antibiotics can clear the underlying problem, though damage already done to the reproductive tract isn’t always reversible. If medications are suppressing sperm count, switching or stopping the drug (under medical guidance) often allows counts to recover over time.
For couples trying to conceive, assisted reproduction techniques like intrauterine insemination or in vitro fertilization can work around a low count by concentrating available sperm or injecting a single sperm directly into an egg.
Supplements and Lifestyle Changes
A large network analysis of randomized trials tested several antioxidant supplements against placebo for men with unexplained low sperm counts. The results were a mixed bag, but a few stood out. Omega-3 fatty acids showed the strongest effect on sperm concentration, increasing it by roughly 10 million per milliliter on average. Coenzyme Q10 added about 5.4 million per milliliter and also improved motility. L-carnitine ranked first for improving both sperm motility (about a 6.5 percentage point increase) and morphology. Zinc, despite its reputation, showed no statistically significant benefit for any sperm parameter in the pooled data.
One important caveat: none of these supplements significantly improved actual pregnancy rates compared to placebo. Better numbers on a semen analysis don’t always translate into a baby. That said, for men with borderline counts who are trying to conceive naturally, even modest improvements in concentration and motility could make a practical difference.
Lifestyle changes with solid evidence behind them include maintaining a healthy weight, avoiding excessive heat to the groin (prolonged hot tub use, laptop computers directly on the lap), limiting alcohol, quitting smoking, and reducing exposure to the environmental chemicals described above. Switching from plastic food containers to glass, choosing fragrance-free personal care products, and eating organic produce when possible can lower phthalate and BPA intake measurably.