A semen analysis measures several features of semen and sperm. Learn how to provide a reliable sample and how current UK reference values are used.
A semen analysis is the main laboratory test used to assess a possible male contribution to fertility problems. It measures the fluid that is ejaculated and several features of the sperm within it. It does not provide a yes-or-no fertility result.
Preparation and collection affect the findings. Follow the instructions from the laboratory performing the test even if they differ slightly from general guidance on this page.
A standard diagnostic analysis may report:
The report may also note round cells, white blood cells, clumping or whether the sample liquefied as expected. These observations need clinical interpretation; they do not automatically show infection or explain a delay in conception.
UK laboratories commonly ask for two to seven days without ejaculation before the sample. Some specify a narrower window, such as three to five days. Use the exact interval given by your laboratory, and record it accurately.
Tell the referring clinician or laboratory about:
Do not change a prescription medicine simply to prepare for the test. Ask the prescriber whether it should be continued.
Instructions vary, but a diagnostic fertility sample will usually be collected as follows:
Do not post a sample unless the service has supplied and validated a postal collection kit. A clinic test and a post-vasectomy semen test also have different protocols, so use the correct instructions.
NICE guideline NG257 uses reference values from the sixth edition of the World Health Organization laboratory manual.
| Measure | WHO reference value used by NICE | What it describes |
|---|---|---|
| Semen volume | 1.4 ml or more | The total fluid collected |
| pH | 7.2 or more | How acidic or alkaline the semen is |
| Sperm concentration | 16 million per ml or more | The number of sperm in each millilitre |
| Total sperm number | 39 million per ejaculate or more | The estimated number in the whole sample |
| Total motility | 42% or more | The proportion of sperm that move |
| Progressive motility | 30% or more | The proportion moving forwards |
| Vitality | 54% or more live sperm | The proportion of sperm that are alive |
| Normal morphology | 4% or more | The proportion meeting strict normal-shape criteria |
These figures are reference values, not targets and not diagnostic cut-offs. They describe the lower fifth centile in a reference population of men whose partners conceived within 12 months. Some men below a reference value conceive naturally, and some men above every reference value experience infertility.
These terms describe laboratory findings. They do not identify the cause and should not be used as a stand-alone forecast of whether conception will occur.
No. Morphology is assessed against very strict laboratory criteria. A result of 4% means that four in every hundred sperm examined met every feature of the reference shape; it does not mean the others are genetically abnormal or incapable of fertilisation. Morphology should be interpreted with count, movement, the laboratory's quality standards and the wider fertility assessment.
Semen parameters naturally vary between ejaculates. The abstinence period, incomplete collection, transport delay, temperature, recent fever or illness and laboratory method may also affect a result. This is why an isolated abnormal test is normally confirmed before a diagnosis or major treatment decision.
The same laboratory is often preferable for a repeat because collection and analysis methods are more comparable. Record the same details honestly rather than trying to produce a “better” sample by abstaining for longer than instructed.
If the first result is abnormal, NICE recommends a repeat confirmatory test. It should ideally be repeated after about three months, allowing the cycle of sperm formation to be completed. If the result shows azoospermia or severe oligozoospermia, the repeat should be performed as soon as possible rather than waiting three months.
A clinician may also repeat a test when collection was incomplete, transport conditions were outside the laboratory's requirements or the findings do not fit the clinical history.
The next step depends on which measures are affected and by how much. After two or more abnormal analyses, NICE recommends a physical examination of the scrotum and testes and consideration of testosterone and gonadotrophin blood tests.
Further tests are selected rather than automatic. They may include:
NICE advises against routine antisperm-antibody testing and against sperm DNA-fragmentation testing in the standard UK fertility pathway. A commercial test is not necessarily useful simply because it measures more variables.
Yes. Semen analysis measures selected features under laboratory conditions. It cannot assess every step required for natural conception, and fertility also depends on the reproductive health and age of the partner trying to become pregnant. Both partners should be assessed together.
