Test
Semen analysis
A semen analysis examines a sperm sample for factors such as the volume, the number of sperm, how well they move, and their shape. It is the main first-line test for the sperm side of fertility, and results are compared against WHO reference values rather than a simple pass or fail.
What it checks
A semen analysis looks at several features of a sperm sample, including semen volume, the number of sperm (concentration), how well they move (motility), and their shape (morphology). Together these help assess the sperm side of fertility.
How the numbers are interpreted
Results are compared with the WHO reference values (6th edition, 2021). It is important to understand that these are lower reference limits taken from a population of fertile men — they describe roughly where the lowest few per cent of fertile men fall. They are a guide to be read alongside the clinical picture, not a pass/fail threshold, and a result below a limit does not by itself diagnose infertility.
Why results are often repeated
Sperm measurements naturally vary between samples and can be affected by recent illness. For this reason, the NHS and NICE advise that an abnormal result is usually confirmed with a repeat test — often around three months later, to allow a full cycle of sperm production — before drawing conclusions or planning treatment such as ICSI.
What it is used for
- Assess sperm number (concentration), movement (motility), and shape (morphology)
- Assess semen volume and other measures
- Help identify a male-factor contribution to infertility
- Guide the choice of treatment, such as ICSI
Preparing for the test
- A short period of abstinence is usually advised — follow the exact instructions from your clinic or laboratory
- Tell the laboratory about recent illness or fever, which can affect results
Important limitations
- A single sample is a snapshot and results vary over time
- Reference values are population-based, so a result within range does not on its own guarantee fertility
- A result below a reference limit is not an automatic diagnosis of infertility
- Written by
- Sam Rivera · Health writer
- Medically reviewed by
- Dr Amir Hassan · Andrologist (medical reviewer)
- Last reviewed
- Next review due
Sources
- WHO laboratory manual for the examination and processing of human semen, 6th editionWorld Health Organization (WHO) · Published 27 July 2021 · Accessed 19 July 2026
- Low sperm countNHS · Published 26 January 2024 · Accessed 19 July 2026
- Fertility problems: assessment and treatment (NICE guideline NG257)National Institute for Health and Care Excellence (NICE) · Published 31 March 2026 · Accessed 19 July 2026
- ReproductiveFacts.org patient resourcesAmerican Society for Reproductive Medicine (ASRM) · Accessed 19 July 2026
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