What is the criterion for oligozoospermia?

The World Health Organization defines oligozoospermia as less than 20 million sperm per ml (milliliter). More recent studies show that in men with proven fertility, the lower limit of normal is around 15 million sperm per ml. Semen Analysis should be done through a Fertility clinic or a Urology lab not a general medical testing lab, and an abnormal result needs a second test 1-2 months later for confirmation.