Semen Analysis: What Each Number on the Report Actually Means

A semen analysis report is a page of numbers with a reference range beside each one, and almost everyone reads it the same way: find the value that fell below the range and assume it is the problem. That reading is wrong often enough to be worth correcting, because of what those reference limits actually are. They are not a line between healthy and unhealthy. They are the fifth percentile of men who got their partner pregnant within a year of trying.

The reference limits

These are the lower reference limits from the sixth edition of the WHO laboratory manual, published in 2021 and used by most laboratories now. The confidence intervals are included because they say something useful about how precise these lines really are.

Note the last row. Four percent normal forms is the threshold, which means a man whose sample is 95 percent abnormally shaped is inside the reference range. That is not a printing error. Human sperm morphology is genuinely poor by the standards of other species, and the strict criteria used to assess it classify almost everything as abnormal.

What the fifth percentile means

This is the single most misread thing on the report, so it is worth being precise.

To build these limits, researchers took men whose partners conceived naturally within twelve months of unprotected intercourse, analysed their semen, and found the value below which the lowest five percent of them sat. Every number in that table is therefore a statement about fertile men, not about infertile ones. One in twenty men who demonstrably fathered a child falls below each line.

Two consequences follow. The first is that a result slightly below a reference limit is weak evidence of anything on its own. The second is that a result comfortably above every limit does not rule out a fertility problem, because the limits were never designed to discriminate; they describe a distribution.

What does carry weight is the pattern. Several parameters low together, a value far below the limit rather than just under it, or a result that stays low across repeat samples all mean considerably more than one borderline figure on one report.

What each parameter measures

Volume. How much fluid was produced. Most of it comes from the seminal vesicles and prostate rather than the testes, so volume says relatively little about sperm production and quite a lot about the accessory glands, the ducts, and whether the whole sample made it into the container. A genuinely low volume can point to retrograde ejaculation, an obstruction, or an incomplete collection, and the last of those is far more common than the first two.

Concentration and total number. Concentration is sperm per millilitre; total number is concentration multiplied by volume. Total number is the more meaningful of the two, because a man with a large volume and modest concentration may deliver more sperm than a man with the reverse. When only one is low, the interaction between them usually explains it.

Motility. Total motility counts everything moving. Progressive motility counts only sperm moving forward in a purposeful way, which is the subset that matters for reaching an egg. Motility is the parameter most sensitive to how the sample was handled: temperature shock, delay, or a lubricant in the collection container will all lower it artificially.

Vitality. The proportion alive, assessed with a stain that only dead cells take up. It is mainly used to interpret very low motility. If motility is near zero but vitality is high, the sperm are alive and something is wrong with their movement apparatus, which points somewhere quite different from sperm that are simply dead.

Morphology. The proportion with normal head, midpiece and tail dimensions under strict criteria. It is the least reproducible parameter in the whole panel, varies most between laboratories, and is the one most likely to change if the same sample is read by a different technician.

Why one test is not an answer

Semen parameters fluctuate substantially in the same man from week to week. A fever, a hard training block, a course of certain medications, or a period of poor sleep can move the numbers, and so can the collection itself.

Three things about collection matter enough to check before accepting a low result. Abstinence should usually be two to seven days; shorter and volume drops, longer and motility does. The entire sample needs to reach the container, because the first fraction carries most of the sperm and losing it can halve the count. And the sample needs to be kept near body temperature and analysed within about an hour, which is why laboratories prefer on-site collection.

The timing of a repeat is not arbitrary either. Spermatogenesis takes roughly two months from start to finish, plus around two weeks of epididymal transit, so anything that affected production will be reflected in a sample taken about three months later. That is also why a lifestyle change made this month cannot be assessed by a test next week.

What changed in 2021

The sixth edition adjusted several limits from the 2010 fifth edition, and the adjustments are smaller than the amount of commentary they generated.

A 2024 study applied both sets of limits to 2,535 semen analyses to see what the change did in practice. Under the 2010 criteria, 42.99 percent of samples met every threshold. Under the 2021 criteria, 43.55 percent did. Twenty-nine samples, about 1.1 percent, were reclassified as normal. The authors concluded that the new limits do not change the proportion of men who require infertility treatment.

That is a useful thing to know if you are comparing an older report with a newer one, or if a clinician mentions that the standards moved. They did, and the movement was close to immaterial.

If a result comes back low

The first step is almost always a second test, taken after about three months, with attention paid to the abstinence interval and the completeness of collection. A single abnormal analysis is not a diagnosis and no competent clinician will treat it as one.

If the second test confirms the first, the investigation widens. That usually means a physical examination looking for a varicocele or absent vas deferens, hormone testing including FSH, LH and testosterone, and depending on the picture, genetic testing or imaging. The specific pattern guides it: very low volume with no sperm points toward obstruction, while high FSH with low counts points toward the testes themselves.

It is also worth saying plainly that an abnormal semen analysis is common and frequently treatable, and that male factor contributes to roughly half of couples presenting with infertility. Getting the test is the difficult part for most men. The report itself is just a distribution with your name on it.

This article is for information only and is not medical advice. Semen analysis results should be interpreted by a clinician alongside your history and examination. Talk to a qualified health professional about your own situation.