Male Fertility: What a Semen Analysis Actually Means

Why this test matters more than it gets treated

Fertility investigation is often framed as something that happens to women, with the male partner tested as an afterthought. The numbers do not support that framing. NICE reports that in the UK, factors in the man cause infertility in about 30% of couples, and that problems are present in both partners in around 40% of infertile couples. Between those two figures, a male factor is involved in a very large share of cases — and it is identified by one non-invasive test that costs a fraction of anything on the female side.

NICE recommends offering both partners further clinical assessment and investigation once the threshold is reached. Not one partner. Both.

The WHO 2021 reference values, in full

Results are compared against reference values from the sixth edition of the WHO laboratory manual for the examination and processing of human semen, published in July 2021. NICE guideline NG257 reproduces them, with 95% confidence intervals:

NICE adds a caveat that is easy to skip and matters: these reference ranges are only valid for the semen analysis tests set out by the WHO. A result from a home testing kit measuring one parameter is not comparable.

What each parameter actually means

Volume is the amount of fluid, most of which comes from the seminal vesicles and prostate rather than the testes. Low volume can reflect an incomplete sample, a short abstinence interval, retrograde ejaculation, or obstruction.

Concentration is sperm per millilitre. Total sperm number is concentration multiplied by volume, and is generally the more meaningful figure — a high concentration in a very small volume is not the same as plentiful sperm.

Total motility counts every sperm that moves at all. Progressive motility counts only those moving forward in a purposeful way, which is the subset that can reach an egg. Progressive motility is the more clinically informative of the two.

Vitality distinguishes sperm that are alive but immotile from sperm that are dead. It matters when motility is very low, because the two have different implications.

Morphology is the percentage with normal shape under strict criteria. The 4% threshold shocks people, and it should not. Strict morphology assessment is deliberately severe; 4% normal forms is the fifth centile among men who conceived within a year. A "96% abnormal" result is not the catastrophe it reads as.

What "below reference" does and does not mean

This is the part almost nobody explains, and it changes how you should read your result.

These values are not diagnostic cut-offs. They are the fifth centile of a distribution measured in men whose partners conceived within 12 months. That means, by construction, 5% of men with proven fertility fall below each one. A result below a reference value does not place you in a category called infertile; it places you in the lower part of a range that includes men who have fathered children.

The sixth edition of the WHO manual is explicit that reference ranges and fifth centiles are insufficient to diagnose infertility, and that the fifth centile is only one way of interpreting a result. The manual also deliberately stepped back from the old diagnostic labels — terms such as "normozoospermia" and "asthenozoospermia" were removed precisely because they encouraged treating a single number as a verdict.

Three further points worth holding:

• Semen parameters vary enormously between samples from the same man. Illness, fever, abstinence interval and sample collection all move the numbers. One result is a snapshot, not a characteristic.
• Being above every reference value does not guarantee fertility, any more than being below one rules it out.
• The numbers describe a population, and you are a person. What matters clinically is the pattern across repeated tests, alongside examination and history.

What happens after an abnormal result

NICE sets out a clear sequence, and knowing it prevents both panic and drift:

• Repeat the test. If the first analysis is abnormal, a repeat confirmatory test should be offered.
• Wait about 3 months for the repeat, to allow a full cycle of sperm formation to complete. The exception: if azoospermia (no sperm) or severe oligozoospermia is found, repeat as soon as possible rather than waiting.
• Two or more abnormal analyses: offer a physical examination of the scrotum and testes, and consider measuring serum testosterone and gonadotrophins.
• Genetic testing where indicated: Y chromosome microdeletion testing for idiopathic azoospermia or concentration under 1 million per mL; CFTR testing for suspected obstructive azoospermia or a vasal abnormality; karyotype for idiopathic azoospermia, and consider it where concentration is persistently under 5 million per mL. Genetic counselling should be offered where a specific defect is found.

What NICE says not to do

Equally useful, because these are things you may be offered privately:

• Do not carry out sperm DNA fragmentation testing.
• Do not offer supplements, antioxidants or medical treatments to improve sperm DNA integrity.
• Do not offer androgens to treat semen abnormalities. Testosterone replacement suppresses sperm production — NICE lists it among drugs to ask about when fertility is a concern.
• Do not offer routine antisperm antibody testing, and do not treat leukocytes in semen with antibiotics without an identified infection.
• Gonadotrophin or anti-oestrogen therapy for impaired semen parameters without hypogonadotropic hypogonadism should only be considered within a clinical trial. Where hypogonadotropic hypogonadism is present, gonadotrophin therapy should be offered.

Where treatment does exist

For varicocele detected on clinical examination, in someone trying to conceive spontaneously with reduced semen parameters, NICE says to consider radiological or surgical treatment, taking female fertility factors into account. For obstructive azoospermia, surgical correction or surgical sperm retrieval; for non-obstructive azoospermia, surgical sperm retrieval, considering micro-TESE. Azoospermia does not automatically mean no genetic children.

Giving a good sample

1. Follow the lab's abstinence instruction exactly — typically 2 to 7 days. Shorter and longer both distort results.
2. Collect the entire sample. The first fraction is the sperm-rich one, and a partially lost sample is a common cause of a falsely poor result.
3. Do not use lubricant or a standard condom unless the lab supplies a fertility-specific collection condom.
4. Keep the sample near body temperature and deliver it within the stated window, usually an hour.
5. Tell the lab about fever or illness in the previous 3 months — it takes about that long for sperm production to recover.

On lifestyle, NICE is measured rather than alarmist: excessive alcohol is detrimental to semen quality, but drinking within 14 units a week spread across several days is unlikely to affect it; smoking is associated with reduced semen quality though the impact on fertility is uncertain; a BMI of 30 or over carries increased risk of reduced fertility; and while elevated scrotal temperature is associated with reduced semen quality, it is uncertain whether looser underwear improves fertility.

When to seek help

A semen analysis should be part of the first round of investigation, at the same time as female testing — not months later. NICE advises assessing both partners after 1 year, and referral at first presentation if the woman trying to conceive is 36 or over, or if either partner has a known or suspected cause. ACOG advises evaluation after 12 months, or 6 months if older than 35.

Ask for testing sooner with a history of undescended testes, testicular surgery or torsion, mumps orchitis after puberty, previous chemotherapy or radiotherapy, current or past anabolic steroid or testosterone use, or a varicocele.

One last thing. A below-reference result is not a statement about masculinity, effort or worth, and men are given almost no cultural script for receiving one. Bring the actual report to the appointment, ask which specific parameter is outside range and by how much, and ask what the repeat test in three months is expected to show. Those are answerable questions, and they are better company than the internet at 2am.