Generally semen analysis is performed following 2-5 days of abstinence for proper standardisation. The sample is obtained by masturbation. The semen analysis normal values should be considered as the minimal standards of adequacy rather than a perfect test of male fertility. As a matter of fact except for complete absence of sperm (azoospermia) in the specimen, there are still no absolute cut-off values to define male infertility in a strict fashion.
For instance 5% of fertile men may have sperm concentration lower than 20 million/ml. Nevertheless the values below these threshold values may be alarming for further work up and each semen analysis should be evaluated within the context of each couple’s history and other findings.