Sperm concentration

The WHO lower reference limit is 16 million/mL; the fertility team interprets the whole picture.

The number of sperm per millilitre of semen. Semen analysis is interpreted as a whole by the fertility team, using WHO reference limits that describe the lower 5 percent of men who fathered a child within a year. A single sample below a limit is repeated after two to three months, because production varies a great deal and takes about ten weeks.

Part of every semen analysis, requested in fertility clinics and after vasectomy (where the aim is no sperm at all).

• A longer gap since the last ejaculation
• Recovery after an illness

• Fever or illness in the previous three months
• Heat, tight clothing, hot baths
• Smoking, alcohol, cannabis and anabolic steroids
• Varicocele
• Some medicines as a class
• A short gap since the last ejaculation
• Blockage or hormonal causes

• Production varies a great deal between samples from the same man
• Abstinence of less than two or more than seven days changes the result
• A sample that reaches the lab late reads poorly

Two to seven days of abstinence, collected into the lab pot, delivered within an hour and kept at body temperature.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.