Average Sperm Count in Men Under Age 45
The lower reference limit for normal sperm concentration is 16 million/mL (15-18 million/mL), with a total sperm number of 39 million per ejaculate (35-40 million per ejaculate), based on the most current World Health Organization reference values adopted by the 2024 AUA/ASRM guidelines. 1
Understanding Reference Values vs. Average Values
The question asks about "average" sperm count, but clinically we use lower reference limits (5th percentile) rather than averages to define normal fertility parameters. 1
- Lower reference limit for sperm concentration: 16 million/mL (95% CI: 15-18 million/mL) 1
- Lower reference limit for total sperm number: 39 million per ejaculate (95% CI: 35-40 million per ejaculate) 1
These values were derived from semen samples of 3,589 males from 12 countries across 5 continents, specifically from men with proven fertility (partners' time-to-pregnancy ≤12 months). 1, 2
Age-Specific Context for Men Under 45
While the WHO reference limits don't stratify by age under 45, research provides important context:
- Young men (ages 18-21): Multiple population studies show median sperm concentrations of 41-55 million/mL in this age group 3
- Sperm counts remain fairly constant between ages 19-29 years 3
- Historical comparison: Data from the 1940s showed averages higher than 100 million/mL, whereas current surveillance studies in Northern Europe show approximately 40% of young men now have counts below 40 million/mL 4
Clinical Significance of Sperm Count Thresholds
Fertility begins to decline when sperm concentrations fall below 30-55 million/mL according to time-to-pregnancy studies, even though the WHO lower reference limit is 15 million/mL. 3
- Below 40 million/mL: May be associated with longer time to pregnancy or subfertility 4
- Below 15 million/mL: Carries high risk of infertility 4
- Below 5 million/mL: Warrants genetic testing (karyotype and Y-chromosome microdeletion screening) when accompanied by elevated FSH, testicular atrophy, or impaired sperm production 1
Important Clinical Caveats
Always obtain at least two semen analyses at least one month apart due to significant intra-individual variability. 1, 2
Proper collection technique is essential: 1, 2
- Abstinence period: 2-3 days before collection
- Transport: Keep at room or body temperature if collected at home
- Analysis timing: Examine within one hour of collection
The reference limits represent the 5th percentile of fertile men, meaning 95% of fertile men have values above these thresholds—this is not the same as an "average" or mean value. 1, 5