Semen Analysis Interpreter (WHO 2021)
Semen Analysis Interpreter (WHO 2021)
Classify a semen analysis against the WHO 2021 sixth-edition lower reference limits — and see why those limits are not fertility thresholds.
Semen Analysis (WHO 2021)
WHO 2021 parameters → patternVolume 2.5 mL, concentration 22 million/mL, progressive motility 34%, normal forms 5%
WHO 2021 lower reference limits (5th centile)
- 5th centile
- the reference limits are the 5th centile of men who fathered a child within 12 months of trying
- reference limit ≠ fertility threshold
- a value below a limit does not mean infertile; a value above every limit does not guarantee fertile
Worked example
Volume 2.5 mL, concentration 22 million/mL, progressive motility 34%, normal forms 5%
Concentration 22 ≥ 16 million/mL
Progressive motility 34% ≥ 30%
Normal forms 5% ≥ 4%
Volume 2.5 mL ≥ 1.4 mL
No rule fires → within reference limits
WHO 2021 lower reference limits
| Parameter | Lower reference limit |
|---|---|
| Volume | 1.4 mL |
| Concentration | 16 million/mL |
| Total count | 39 million |
| Progressive motility | 30% |
| Total motility | 42% |
| Normal forms | 4% |
| Vitality | 54% |
Reference limits, not fertility thresholds
The WHO 2021 sixth-edition lower reference limits are the 5th centile of semen parameters measured in men who fathered a child within 12 months of trying: volume 1.4 mL, concentration 16 million/mL, total count 39 million, progressive motility 30%, total motility 42%, normal forms 4%, and vitality 54%.
The critical point to hold onto is that these are reference limits from fertile men, not thresholds for fertility. A man below one or more limits is not infertile, and a man above every limit is not guaranteed fertile — the distributions of fertile and subfertile men overlap heavily across every parameter, and semen analysis alone cannot draw a hard line between the two. It should be interpreted as one part of a couple’s fertility assessment, not read in isolation as a verdict.
Two practical points affect the result more than most people expect. Abstinence should be between two and seven days before collection — outside that window, both count and motility shift for reasons unrelated to underlying fertility. And any abnormal result should be confirmed on a repeat sample taken at least three months later, since spermatogenesis takes about 74 days and a febrile illness or other recent illness can depress a single sample without reflecting the man’s usual parameters.
Frequently asked questions
Do the WHO 2021 reference limits mean I am infertile if I am below them?
No. They are the 5th centile of fertile men, not a fertility threshold. Many men with values below one or more limits go on to father children naturally, and the reference limits describe a population, not an individual prediction.
Does a normal semen analysis guarantee fertility?
No. A result above every reference limit does not guarantee fertility — the distributions of fertile and subfertile men overlap substantially on every parameter measured.
How long should abstinence be before a semen analysis?
Two to seven days. Outside that window, both concentration and motility can shift for reasons unrelated to a man’s usual fertility, which is why the WHO specifies the interval.
Why should an abnormal result be repeated?
Spermatogenesis takes about 74 days, so a single sample can be affected by a recent febrile illness or other transient factor. Repeating at least three months later gives a result representative of current, steady-state production.
Related calculators
References
- World Health Organization. WHO Laboratory Manual for the Examination and Processing of Human Semen. 6th edn. Geneva: WHO; 2021.
- Practice Committee of the American Society for Reproductive Medicine. Diagnostic evaluation of the infertile male: a committee opinion. Fertil Steril. 2021;115(1):54–61.
Not medical advice. For healthcare professionals and education. Reference intervals vary by laboratory and assay — always use your own laboratory's. Never base a dose or a treatment decision on this page alone. Full disclaimer at calcengines.com/disclaimer/