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Semen Analysis Explained with Andrologist Stuart Dawe Long

Semen Analysis Explained with Andrologist Stuart Dawe Long
Authored by
Shaun Greenaway

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A semen analysis checks the volume of semen and the number, movement, shape and, when needed, vitality of sperm in the sample. The figures must be considered together and alongside your medical history. A result below a reference value does not by itself prove infertility, and an abnormal first result will usually need to be repeated.

What is a semen analysis?

A semen analysis is the main laboratory test used to assess male fertility. A trained laboratory team examines a fresh semen sample using standardised methods. The result can help identify whether there may be a male-factor fertility problem and whether further investigation is appropriate.

The test does not provide a simple fertile or infertile verdict. Semen measurements vary between men and between samples from the same man. Pregnancy also depends on factors affecting both partners, so the result needs to be interpreted in the context of the couple.

In the original Male Fertility Hub session accompanying this article, andrologist Stuart Dawe-Long explains why the full result matters, the difference between a clinical laboratory test and many home kits, and what may happen after an unusual result. The factual guide below has been expanded to make those points easier to find and use. Any transcript-specific wording should be checked against the recording before publication.

What do the numbers on a semen-analysis result mean?

The 2026 NICE fertility guideline uses the following lower reference values, based on World Health Organization laboratory methods. They describe measurements seen at the lower end of a reference population. They are not a dividing line between fertile and infertile men.

Semen volume

  • What it means: The amount of fluid in the complete sample
  • Lower reference value: 1.4 ml

Sperm concentration

  • What it means: The number of sperm in each millilitre
  • Lower reference value: 16 million/ml

Total sperm number

  • What it means: The number of sperm in the whole sample
  • Lower reference value: 39 million per ejaculate

Total motility

  • What it means: The proportion of sperm showing any movement
  • Lower reference value: 42%

Progressive motility

  • What it means: The proportion moving forwards
  • Lower reference value: 30%

Vitality

  • What it means: The proportion of sperm that are alive
  • Lower reference value: 54%

Morphology

  • What it means: The proportion with a typical shape under strict assessment
  • Lower reference value: 4%

pH

  • What it means: How acidic or alkaline the semen is
  • Lower reference value: 7.2

Reference values are only meaningful when the sample has been collected and analysed using appropriate procedures. Your report may also include laboratory-specific ranges or comments, so ask the referring clinician or laboratory to explain the complete result.

Semen volume

Volume is the amount of semen produced, not the sperm count. A low volume can sometimes occur because part of the sample was missed during collection. It can also be associated with other factors that need clinical assessment. Tell the laboratory if the complete sample was not collected.

Sperm concentration and total sperm number

Concentration is the number of sperm in each millilitre of semen. Total sperm number takes the concentration and the sample volume into account. These are related measurements, but they are not interchangeable.

A low sperm concentration is called oligozoospermia. No sperm seen in the ejaculate is called azoospermia. These findings need confirmation and further investigation rather than assumptions about the cause.

Motility

Motility describes how sperm move. Progressive motility refers to sperm moving forwards, while total motility includes other movement as well. Low motility is sometimes called asthenozoospermia.

The percentage needs to be interpreted alongside the number of sperm present. A clinician should consider the complete pattern rather than one figure in isolation.

Morphology

Morphology is the proportion of sperm assessed as having a typical shape under strict laboratory criteria. The lower reference value of 4% often looks alarming, but it does not mean that the remaining sperm are incapable of fertilisation. Morphology is one part of a wider result and should not be interpreted on its own.

Vitality

Vitality measures the proportion of sperm that are alive. It can be particularly useful when many sperm appear not to be moving, because an immotile sperm is not necessarily a dead sperm.

pH and other observations

The report may include pH, viscosity, liquefaction time, white blood cells or other observations. An unusual value may have several possible explanations and is not a diagnosis by itself. Ask whether it is clinically significant in the context of your other results.

How should you prepare for a semen analysis?

Follow the instructions from your own clinic or andrology laboratory, because requirements can differ. UK laboratories commonly ask you to avoid ejaculation for around two to five days before producing the sample. A shorter or longer period can affect some measurements.

You will usually be asked to:

  • Wash your hands and penis as instructed
  • Produce the sample by masturbation into the sterile container supplied by the clinic
  • Avoid ordinary condoms, lubricants or other containers unless the laboratory has specifically approved them
  • Collect the entire sample and tell the laboratory if any was missed
  • Record the collection time and the period since your last ejaculation
  • Keep the sample at the temperature and deliver it within the time stated by the laboratory if it is produced at home

Do not guess at the transport window. Some laboratories require production on site, while others accept a home-produced sample under specific conditions.

Tell the clinic about recent fever or illness, medication, testosterone treatment, anabolic steroids and recreational drug use. These details can affect interpretation or the next steps. Do not stop prescribed medicine without speaking to the clinician responsible for your care.

For more detail, read How Abstinence Timing Affects Male Fertility Testing.

Does one abnormal result mean you are infertile?

No. A single abnormal semen analysis does not prove that you are infertile. Results can vary because of normal biological variation, collection problems, the length of abstinence, recent illness and other short-term or longer-term factors.

It is possible to conceive naturally with measurements below a reference value, while a result above every reference value does not guarantee pregnancy. The result is evidence that helps guide a wider fertility assessment.

What happens after an abnormal semen analysis?

The 2026 NICE fertility guideline recommends a repeat confirmatory semen analysis when the first result is abnormal. This should ideally take place about three months later, allowing time for the sperm-production cycle. If the result shows azoospermia or severe oligozoospermia, the repeat should be arranged as soon as possible.

After two or more abnormal results, NICE recommends a physical examination of the scrotum and testicles. Testosterone and gonadotrophin blood tests may also be considered. Depending on the findings, the next step could include referral to an andrologist, urologist or fertility specialist, or further imaging or genetic investigations.

Ask for a copy of the complete report and a clear explanation of:

  • Which measurements were outside the laboratory reference range
  • Whether the complete sample was collected and analysed under suitable conditions
  • When and where the test should be repeated
  • Whether your history, examination or medication suggests a possible cause
  • Whether you need a specialist male-fertility assessment

Read Male Fertility Testing Through Your GP for a fuller explanation of the UK assessment pathway.

What does azoospermia mean?

Azoospermia means that no sperm were seen in the semen sample. It does not automatically mean that the testicles produce no sperm. Possible explanations include a blockage, impaired sperm production, hormonal causes and, occasionally, a collection or laboratory issue.

The finding should be confirmed promptly and investigated by an appropriately experienced clinician. Some men may have treatment options or may be able to have sperm retrieved for fertility treatment, depending on the cause. Avoid drawing conclusions from the word alone before the repeat test and specialist assessment.

Is a home sperm test the same as a laboratory semen analysis?

Usually not. Home tests vary considerably. Some estimate only sperm concentration or motility, while a full clinical semen analysis assesses several measurements using validated laboratory procedures. A reassuring home result may therefore miss an issue in a parameter that the kit does not measure.

A home test can sometimes be a useful first step, but it should not replace a diagnostic laboratory analysis when you have fertility concerns, have been trying to conceive without success or have relevant symptoms or medical history.

For a closer look at the limitations and potential uses, read The Growth of Home Sperm Testing.

Can lifestyle changes improve the result?

General health can influence reproductive health, but no supplement, diet or short programme can guarantee a normal semen analysis or pregnancy. Sensible steps include not smoking, avoiding anabolic steroids and recreational drugs, keeping alcohol within UK guidelines, aiming for a healthy weight and discussing workplace or heat exposures with a clinician when relevant.

If you take prescribed testosterone and want to conceive, seek medical advice. Testosterone treatment can suppress sperm production, but you should not stop it without a supervised plan.

Be cautious about expensive supplements or tests promoted as a universal solution. Ask what evidence supports them, whether there are risks and whether the result would change your care. You can also read How to Know if Your Sperm Health Is on Track.

Questions to ask about your semen-analysis result

  • Can you explain the volume, concentration, total number, motility and morphology together?
  • Were there any collection or transport issues that could have affected the result?
  • Does this result need to be repeated, and if so, when?
  • Are any medicines, hormones, illnesses or exposures relevant?
  • Do I need a physical examination, hormone tests or a specialist referral?
  • If a treatment or extra test is suggested, how would its result change the plan?
  • Should my partner and I be investigated at the same time?

The most important thing to remember

A semen analysis is a starting point, not a verdict. Look at the whole report, confirm an abnormal result as advised and ask for the possible causes to be investigated. You deserve more than being told that a result is simply good or bad without an explanation of what it means and what happens next.

If testing or treatment is affecting your mental health or relationship, you can join The Male Fertility Hub community to connect with people who understand the process.

Sources

This article provides general information and does not replace individual medical advice. Speak to your GP, andrologist or fertility specialist about your circumstances.