The semen analysis is done on an ejaculated sample collected after masturbation. It is best to do this test after a patient has abstained from sexual activity for two to five days. The test can be inaccurate if there has been recent ejaculation (counts too low) or if ejaculation has not occurred in a long time (too many dead sperm).
Once the sample has been taken to the laboratory, it is analyzed for many different parameters, including fluid volume, sperm numbers, sperm motility (the percentage of moving sperm), and sperm morphology (the shape and appearance of the sperm). Variations can occur from test to test, even in the same man, and sometimes the test needs to be repeated.