Semen concentration measures the number of sperm cells per millilitre of ejaculate. It is one of the key parameters of a semen analysis (spermogram) and reflects the ability of the testes to produce sperm. Along with total motility and morphology, concentration is used to assess male fertility potential.
The WHO 2021 reference value for semen concentration is 16 million sperm per millilitre as a lower reference limit (5th percentile of fertile men). Concentrations below this (oligospermia) are associated with reduced fertility. Severely low concentration (below 5 million/mL) is called severe oligospermia; absence of sperm is azoospermia, which requires specialist urology investigation.
FAQs
What is the difference between concentration and total sperm count?
Concentration is sperm per millilitre; total sperm count is concentration multiplied by semen volume. Both are reported in a semen analysis. Total sperm count is often considered more relevant for fertility than concentration alone, as it reflects the total sperm available per ejaculate.
Can sperm concentration be zero?
Yes. Azoospermia (no sperm in the ejaculate) can be caused by testicular failure (non-obstructive) or genital tract obstruction (obstructive). Both types require specialist urology or andrology assessment.
How many times should a semen analysis be repeated?
Semen parameters vary significantly between samples. Two semen analyses at least 4 weeks apart under standardised conditions (2-7 days abstinence) are recommended before drawing conclusions about a man's fertility status.
Does age affect sperm concentration?
Semen volume and sperm concentration decline modestly with advancing male age. DNA fragmentation, morphology, and motility are affected more significantly by age than concentration alone.
