Is a Decrease from 56 to 42 Million/mL Clinically Significant?
This decrease is not clinically meaningful and does not warrant concern or intervention. Both values fall well within the normal fertile range, and the observed variation is consistent with expected biological and technical variability in semen analysis.
Understanding Normal Variability in Sperm Concentration
Semen analysis exhibits substantial intra-individual variability, which is why the WHO guidelines strongly recommend analyzing at least two ejaculates separated by 2-3 months before making clinical decisions 1.
Both your initial concentration of 56 million/mL and repeat value of 42 million/mL exceed the WHO lower reference limit of 16 million/mL by considerable margins (3.5-fold and 2.6-fold respectively) 2.
Concentrations above 40 million/mL are associated with optimal fertility potential, and your repeat value of 42 million/mL remains in this optimal range 2.
Why This Variation Is Expected
Studies examining temporal changes in sperm parameters using WHO reference data found that the 5th percentile of sperm concentration remained stable over decades (14.9-18 million/mL), while mean values showed minor fluctuations (77.2-88.1 million/mL) 3.
Natural biological variation between samples is normal and expected, influenced by factors such as abstinence period, hydration status, recent illness, stress, and minor technical differences in laboratory handling 1.
Research demonstrates that fecundity only begins to decline when sperm concentrations fall below 30-55 million/mL, and even then, fertility remains possible 4.
Clinical Thresholds That Actually Matter
The critical thresholds you should be aware of are:
- Below 16 million/mL: Below WHO reference range, associated with increased infertility risk 2
- Below 5 million/mL: Severe oligospermia requiring genetic testing (karyotype and Y-chromosome microdeletion screening) 2
- Total motile sperm count (TMSC) below 10 million: Indicates need for assisted reproductive techniques 2
Your values are nowhere near these concerning thresholds.
What You Should Do
No action is required. Your sperm concentration remains in the normal-to-optimal range. However, if you want reassurance:
Ensure proper collection technique: 2-3 days abstinence before collection, transport at room or body temperature, and analysis within one hour 2
Avoid factors that temporarily impair spermatogenesis: smoking, excessive alcohol, obesity (BMI >25), heat exposure to testes, and never use exogenous testosterone or anabolic steroids if fertility is desired 5
If planning conception, a TMSC >10 million per ejaculate is associated with good natural conception rates, and your parameters likely exceed this threshold 2
Important Caveat
A single parameter (sperm concentration) is insufficient for fertility assessment. The WHO strongly recommends evaluating multiple ejaculate parameters together—concentration, motility, morphology, and volume—as this combination is far more predictive of fertility than concentration alone 1. If you have concerns about fertility, request a complete semen analysis with all parameters assessed, not just concentration.