Dozens of factors can lower sperm count, ranging from everyday habits like smoking to prescription medications and chemical exposures. Some causes are temporary and reversible within a few months, while others require medical intervention. Because a full cycle of sperm production takes about 64 days, most factors that harm sperm count do so by disrupting that ongoing process, and improvements after removing the cause generally follow the same timeline.
Smoking and Tobacco
Smoking is one of the most well-documented lifestyle factors behind lower sperm counts. On average, men who smoke have sperm concentrations about 22% lower than nonsmokers, and the effect is dose-dependent: the more you smoke, the greater the reduction. Smokeless tobacco products like chewing tobacco show a similar pattern, with multiple sperm quality markers declining as usage increases.
The silver lining is that smokers’ sperm numbers often still fall within the technically “normal” range, so smoking alone may not cause infertility. But if your count is already on the lower end, that 22% hit could be the difference between conceiving naturally and needing help. Quitting gives your body a chance to recover over the next two to three months as a fresh cycle of sperm develops.
Testosterone and Anabolic Steroids
This is one of the most common and least understood causes of dramatically low sperm counts in younger men. Taking testosterone replacement therapy or anabolic steroids for muscle building sends a signal to your brain that there’s already plenty of testosterone in the bloodstream. Your brain responds by shutting down the hormonal signals that tell your testicles to produce sperm. Testosterone levels inside the testicles can drop so low that sperm production slows to a trickle or stops entirely, a condition called azoospermia, meaning zero sperm in the ejaculate.
The irony is striking: men take testosterone to feel more masculine, and the result is often temporary infertility. Recovery after stopping is possible for most men, but it can take many months and isn’t guaranteed. If you’re planning to have children, testosterone supplementation and anabolic steroids are among the most important things to avoid.
Other Medications That Lower Sperm Count
Several classes of prescription drugs can reduce sperm production or interfere with ejaculation:
- Chemotherapy drugs can significantly decrease or completely halt sperm production. Men facing cancer treatment are often advised to bank sperm beforehand.
- Opioids used long-term disrupt the hormonal signals that control testosterone production, reducing both the quantity and quality of sperm.
- Alpha-blockers prescribed for prostate or urinary problems (such as tamsulosin) can sharply reduce ejaculation volume or prevent ejaculation altogether.
- SSRIs prescribed for depression and anxiety can cause sexual dysfunction, including delayed ejaculation, and may affect sperm quality.
If you’re taking any of these and trying to conceive, it’s worth discussing alternatives with your prescriber rather than stopping on your own.
Endocrine-Disrupting Chemicals
Certain synthetic chemicals mimic or interfere with your hormones, and some have been linked to lower sperm counts. The most studied include phthalates (found in plastics, personal care products, and food packaging), bisphenol A or BPA (in some plastics and can linings), and organochlorine compounds like PCBs and DDT residues that persist in the environment.
A study of over 1,000 men at a Chinese infertility clinic found that higher levels of a common phthalate breakdown product were associated with lower sperm concentration and total sperm count. When phthalates were measured directly in semen, higher levels correlated with reduced sperm motility and semen volume. PCB exposure has also been linked to lower sperm motility and DNA damage within sperm cells.
What makes these chemicals particularly concerning is that exposure is nearly universal. They leach from food containers, enter water supplies, and absorb through skin from cosmetics and fragrances. Reducing exposure means practical steps like avoiding heating food in plastic containers, choosing fragrance-free personal care products, and opting for glass or stainless steel food storage when possible. There’s also evidence that some of the damage may begin before birth: chemical exposures during a critical window of fetal development (roughly weeks 8 through 14 of pregnancy) can affect how the male reproductive system forms, with consequences that show up decades later.
Diet and Processed Meat
What you eat appears to influence sperm quality more than many men realize. A study of men attending a fertility clinic found that each additional daily serving of processed meat was associated with a 56% higher risk of abnormally low sperm motility. Processed meats like bacon, sausage, and deli meats are significant sources of saturated fats, trans fats, and synthetic compounds that can act as weak estrogen mimics in the body.
The broader dietary pattern matters too. Diets high in trans fats and low in fruits, vegetables, and fish tend to correlate with poorer semen quality across multiple studies. You don’t need a perfect diet, but shifting toward whole foods and away from heavily processed ones gives your sperm production better raw materials to work with.
Body Weight and Fat Distribution
The relationship between weight and sperm count is more nuanced than a simple “obesity equals low sperm.” A recent study in Frontiers in Endocrinology found no statistically significant difference in total sperm count between obese and non-obese men when looking at BMI alone. But when researchers looked at where fat was stored, the picture changed considerably.
Men with “generalized obesity,” carrying excess fat throughout the body, had median sperm concentrations of about 74 million per milliliter. Men with “simple obesity” (high BMI but without the waist measurement to match) had even lower concentrations, around 62 million per milliliter. Yet men with “central obesity,” fat concentrated around the midsection, actually had higher concentrations than either group at about 151 million per milliliter. The takeaway is that overall body composition and fat distribution may matter more than the number on the scale, and that the hormonal disruption from excess body fat affects men differently depending on how that fat is distributed.
Cannabis and Alcohol
Despite widespread assumptions, the evidence on cannabis and sperm count is surprisingly mixed. Studies across geographically diverse populations of men at infertility clinics have found either no meaningful association or inconsistent links between marijuana use and sperm parameters like concentration, motility, and morphology. That doesn’t mean cannabis is harmless for fertility, but the data doesn’t support the same clear-cut relationship seen with tobacco.
Alcohol sits in a similar gray zone. Heavy drinking is broadly associated with hormonal disruption and testicular damage, but research hasn’t established a clean threshold, a specific number of drinks per week, where sperm count reliably drops. Moderate drinking likely poses minimal risk for most men, while chronic heavy use is more clearly harmful.
Heat Exposure
Testicles hang outside the body for a reason: sperm production requires temperatures slightly below core body temperature. Sustained heat exposure from sources like hot tubs, saunas, laptops placed directly on the lap, and prolonged sitting can raise scrotal temperature enough to impair sperm production.
That said, the body has effective cooling mechanisms. A study comparing 90 fertile workers in high-temperature environments with 40 controls found no significant differences in scrotal temperature or semen quality, suggesting that acclimatization can compensate for environmental heat to a degree. Occasional sauna use or a warm bath is unlikely to cause lasting harm, but consistent, prolonged heat exposure, especially from sources pressed directly against the body like laptops, is worth minimizing if you’re trying to conceive.
How Long Recovery Takes
The full cycle of sperm production, from the initial stem cell division to mature sperm ready for ejaculation, takes about 64 days. This means that any change you make today, whether quitting smoking, stopping a medication, or reducing chemical exposure, won’t show results in a semen analysis for roughly two to three months.
This timeline also works in reverse. A high fever, a course of medication, or a few weeks of heavy drinking can temporarily tank your numbers, but a single bad semen analysis doesn’t necessarily reflect your long-term fertility. Repeating the test after two to three months gives a more accurate picture. For men recovering from testosterone or steroid use, the timeline can stretch considerably longer, sometimes six months to a year or more, as the hormonal signaling pathway gradually restarts.