Low semen quantity — does it affect fertility?

Low semen volume is called hypospermia. Under the WHO 6th edition reference values (2021), the lower reference limit for semen volume is 1.4 mL — note this differs from the older 5th edition (2010) figure of 1.5 mL that many labs and websites still quote. An important distinction: semen volume and sperm count are separate parameters. You can have normal volume with a low count, or low volume with a normal concentration. They point to different problems. Low volume can result from retrograde ejaculation (semen passing backwards into the bladder), obstruction of the ejaculatory ducts, hormonal problems, a short abstinence period before the sample, or simply an incomplete collection — the first portion of the ejaculate carries most of the sperm, and losing it skews the result. Because of that last point, a single abnormal result should not be treated as conclusive. A repeat analysis after 2–7 days of abstinence, at a properly accredited andrology laboratory, is the correct next step. Please see a urologist or andrologist to interpret the full report rather than any single number.

For reference, the WHO 6th edition (2021) lower fifth percentile values are: semen volume 1.4 mL, sperm concentration 16 million/mL, total sperm number 39 million per ejaculate, total motility 42%, progressive motility 30%, vitality 54%, and normal forms 4%. Importantly, WHO states these do not represent a limit between fertile and infertile men — they describe where 95% of men who conceived naturally within a year fell. There is substantial overlap between fertile and infertile men on every parameter.