A semen analysis measures how much semen a man produces, along with the number and quality of sperm in the sample. It is usually one of the first tests carried out to find out whether a man has difficulty fathering a child. A problem with the semen or sperm affects more than one-third of couples who are unable to conceive.
The measurements taken during a semen analysis include:
- Volume: how much semen is present in a single ejaculation.
- Liquefaction time: semen is a thick gel when ejaculated and normally turns to liquid within 20 minutes. Liquefaction time is how long this takes.
- Sperm count: the number of sperm present per millilitre (mL) of semen.
- Sperm morphology: the percentage of sperm with a normal shape.
- Sperm motility: the percentage of sperm that move forward normally. The number of sperm showing normal forward movement in a given volume of semen, known as motile density, may also be measured.
- pH: a measure of the acidity (low pH) or alkalinity (high pH) of the semen.
- White blood cell count: white blood cells are not normally present in semen.
- Fructose level: the amount of fructose, a sugar that provides energy for the sperm.
Why it is done
A semen analysis is done to find out whether:
- a man has a reproductive problem that is causing infertility;
- a vasectomy has been successful;
- a vasectomy reversal has been successful.
How to prepare
You may be asked to avoid any sexual activity that results in ejaculation for 2 to 5 days before the test. This helps ensure that your sperm count is at its highest and makes the test more reliable. However, try not to abstain for more than 1 to 2 weeks beforehand, as a long gap can result in less active sperm.
You may also be asked to avoid drinking alcohol for a few days before the test.
Normal values
A few of the common normal ranges are listed below:
- Volume normally ranges from 1.5 to 5.0 millilitres per ejaculation.
- Sperm count normally ranges from 20 to 150 million sperm per millilitre.
- At least 60% of the sperm should have a normal shape and show normal forward movement (motility).
Normal ranges may vary slightly between laboratories, so talk to your doctor about what your specific results mean. Some laboratories use different measurements or test different specimens, so the examples above are a general guide only.
It is not always straightforward to interpret the results of a semen analysis. An abnormal result does not necessarily mean there is a problem with a man's ability to father children.
What abnormal results mean
Abnormal results may point to a fertility problem. For example, a sperm count that is very low or very high can reduce fertility. The acidity of the semen and the presence of white blood cells, which may suggest an infection, can also affect fertility, as can abnormal sperm shape or movement.
However, there are still many unknowns in male infertility. Further testing may be needed if abnormalities are found, and many of these problems are treatable. To understand the wider picture, read our guide on male infertility causes and treatment options.
Risks
There are no risks associated with a semen analysis.
Considerations
The following can affect a man's fertility:
- Alcohol
- Many recreational and prescription drugs
- Tobacco
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