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.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.