The WHO laboratory manual for the examination and processing of human semen is the reference standard for semen analysis, and its sixth edition, published in 2021, reset the lower reference limits against a larger and more geographically diverse dataset than the 2010 edition. The limits are not diagnostic thresholds — they describe the fifth percentile of a fertile population, so a value below a limit means the parameter is in the lowest 5% of men who have fathered a child, not that the man is infertile.
The 2021 lower reference limits
The sixth edition sets the following fifth-percentile limits: volume ≥1.4 mL, total sperm number ≥39 million per ejaculate, concentration ≥16 million/mL, total motility ≥42%, progressive motility ≥30%, vitality ≥54%, and normal morphology ≥4% by Kruger strict criteria. A sample is described as normal when every parameter meets or exceeds its limit; a single abnormal parameter does not by itself establish male factor infertility.
A worked example
A sample with 2.0 mL volume, 45 million total sperm, 22 million/mL concentration, 38% total motility, 25% progressive motility, and 3% normal morphology is abnormal on three counts: total motility, progressive motility, and morphology. The volume, total count, and concentration are all above their limits. The pattern — adequate numbers but poor motility and morphology — points toward a functional or morphological problem rather than a production problem, and would justify a repeat analysis in two to four weeks before any conclusion is drawn.
Common mistakes
Semen parameters are highly variable within an individual, so a single abnormal sample is not diagnostic; the WHO manual requires at least two samples taken at least two weeks apart. Abstinence interval matters: too short and the count falls, too long and motility and morphology degrade. The sample must be collected at the laboratory and analysed within an hour, because motility declines quickly at room temperature. Finally, the 2021 limits are lower than the 2010 limits for several parameters, so a sample that was borderline under the old manual may be normal under the new one.
Source and disclaimer
Source: World Health Organization, WHO laboratory manual for the examination and processing of human semen, 6th edition, 2021. Educational use only — semen analysis must be interpreted by a clinician alongside history, examination, and partner evaluation, and is not a substitute for a fertility assessment.