Interactive guide · Understanding investigations
Understanding a semen analysis report
Find the lines your own report has, from the most basic to the most specialist.
Grouped by report type · open any line
This explains the report, not your results. It sets out what each line on a semen analysis is and where the reference values come from. It does not interpret anyone’s own report.
Find the lines your own report has
Reports differ. A sample requested by a GP may carry five lines; one from a fertility clinic may carry twenty. The groups below run from what almost every report has to tests ordered for a specific question, so you can start at the group your own report matches and ignore the rest.
Some lines sit inside others. Progressive motility is not a separate measurement from motility, it is a sharper reading of it, so it is nested underneath rather than listed alongside.
On almost every report
The handful of lines a basic sample is asked for, including one requested by a GP.
Reference value
1.4 mL or moremL
Lower limit — results at or above it are unremarkable
Source: WHO 6th edition (2021)
What it measures
The amount of fluid in the whole sample. Most of it comes from the seminal vesicles and the prostate rather than from the testes, so volume speaks more about those glands and the ducts carrying their fluid than about sperm production.
What it does and does not tell you
Volume rises with a longer gap since the last ejaculation and falls with a shorter one, so it is read alongside the abstinence period rather than on its own. It also sets the total sperm number, which is concentration multiplied by volume: the same concentration in a larger volume means more sperm altogether. A very low volume with no sperm points somewhere quite different from a normal volume with no sperm, which is why the figure is recorded even when it looks unremarkable.
Reference value
16 million/mL or moremillion/mL
Lower limit — results at or above it are unremarkable
Source: WHO 6th edition (2021)
What it measures
How many spermatozoa are present in each millilitre of semen, counted under a microscope on a ruled counting chamber.
What it does and does not tell you
It is the number most people look at first, and on its own the easiest to misread, because it moves with the amount of fluid the sample happens to contain: the same production in less fluid reads as a higher concentration. That is why the report also gives a total, and why the two are read together. A concentration below the reference limit is called oligozoospermia — a description of a number, not an explanation of it.
Finer readings of this same line
Reference value
39 million or moremillion per ejaculate
Lower limit — results at or above it are unremarkable
Source: WHO 6th edition (2021)
What it measures
Concentration multiplied by volume: the number of spermatozoa in the whole ejaculate rather than in each millilitre.
What it does and does not tell you
Generally the better reflection of what the testes are producing, because it is not distorted by how much seminal fluid was added. Where the total and the concentration seem to disagree — a low concentration with an adequate total, or the reverse — the volume usually accounts for it, and the collection conditions recorded further down explain the rest.
Reference value
Reported as the breakdown below rather than as one figure
What it measures
How many spermatozoa are moving, assessed on a warmed slide. It is reported as the breakdown below rather than as a single figure.
What it does and does not tell you
Motility falls with delay and with cold, so a sample produced at home and carried across town can read lower than the same man’s sample produced at the laboratory. The interval between production and examination is recorded for exactly this reason, and a low figure is read against it rather than at face value.
Finer readings of this same line
Reference value
42% or more%
Lower limit — results at or above it are unremarkable
Source: WHO 6th edition (2021)
What it measures
The proportion of spermatozoa that move at all, whether or not they are going anywhere: progressive and non-progressive added together.
What it does and does not tell you
The broader of the two motility figures, and the less informative, because it counts a sperm vibrating on the spot alongside one swimming steadily forwards. Its main use is as a cross-check against vitality: spermatozoa that do not move but are nonetheless alive point somewhere different from ones that are dead.
Reference value
30% or more%
Lower limit — results at or above it are unremarkable
Source: WHO 6th edition (2021)
What it measures
The proportion moving actively forwards, in a line or a large circle, rather than vibrating in place.
What it does and does not tell you
The more useful of the two motility figures, which is why it carries the tighter limit. Reduced progressive motility is called asthenozoospermia. Like every other count here it varies between samples from the same man, so one figure below the limit describes one sample rather than a settled state.
Reference value
From the 1999 WHO manual; superseded but still printed by some laboratories
What it measures
An older four-way grading — rapid progressive, slow progressive, non-progressive and immotile — from the 1999 WHO manual. Some laboratories still report it.
What it does and does not tell you
The current manual replaced it with the simpler progressive, non-progressive and immotile split, because separating rapid from slow depended too heavily on the observer. Grades a and b together correspond roughly to progressive motility and grade c to non-progressive, but the correspondence is approximate: figures from the two schemes are not interchangeable and comparing them directly misleads.
Reference value
4% or more%
Lower limit — results at or above it are unremarkable
Source: WHO 6th edition (2021)
What it measures
The proportion of spermatozoa whose head, midpiece and tail all match a narrow template, judged on a stained smear under strict criteria.
What it does and does not tell you
The 4% limit is not a misprint. Strict criteria score anything short of an ideal form as abnormal, so most spermatozoa in most fertile men are classed abnormal and 4% falls at the fifth centile. Morphology is also the least reproducible figure on the report — the stain, the criteria and the person at the microscope all move it, and the same sample can be scored differently by two laboratories. A low figure in isolation therefore carries less weight than the pattern across a whole report. Reduced normal forms is called teratozoospermia.
Reference value
2 to 7 days
Source: WHO laboratory manual
What it measures
How long since the last ejaculation, recorded from what the man reports rather than measured. It is a collection condition, not a result.
What it does and does not tell you
Volume and total sperm number both accumulate between ejaculations, so a short interval lowers them and a long one raises them. Comparing two samples without comparing their abstinence periods can invent a change that is not there. A very long interval is not an advantage either: motility and vitality tend to fall as spermatozoa are stored, which is why the recommended window has an upper end as well as a lower one.
Reference value
Within 60 minutes
Upper limit — results at or below it are unremarkable
Source: WHO laboratory manual
What it measures
The interval between producing the sample and examining it. A collection condition rather than a result.
What it does and does not tell you
Motility falls steadily after production, and faster if the sample cools. A long interval, or a cold journey, lowers the motility and vitality figures without anything having changed in the man. Where the interval was long, those figures are read with that in mind.
Reference value
Recorded as a note, not measured
What it measures
Whether the whole ejaculate reached the container, recorded as a note when any was spilled or missed.
What it does and does not tell you
The first fraction of the ejaculate carries most of the spermatozoa, so losing the beginning of a sample lowers the concentration and the total number far more than losing the end. An incomplete collection is one reason an unexplained low count is sometimes not reproduced on the next occasion.
On a full laboratory report
What a laboratory following the WHO manual reports as a matter of course.
Reference value
Described, not measured
What it measures
The colour and opacity of the sample, described by eye: normally greyish and opalescent.
What it does and does not tell you
A property to be described rather than measured, and informative only at the extremes. A clear, watery sample often accompanies a very low sperm concentration. A yellow tint can follow a long abstinence period, jaundice, or certain medicines. A red or brown tinge means blood, which has a range of causes and is recorded rather than interpreted from the sample alone.
Reference value
Within 60 minutes
Upper limit — results at or below it are unremarkable
Source: WHO laboratory manual
What it measures
How long the sample takes to change from the gel it forms on ejaculation into a free-flowing liquid, a process driven by prostatic enzymes.
What it does and does not tell you
A ceiling rather than a floor: a short time is the unremarkable result, and reading this line as though it had a minimum inverts its meaning. Delayed liquefaction makes a sample hard to mix and pipette, so it can depress the concentration and motility figures for technical reasons rather than biological ones. Where it was delayed, the laboratory records what it did to help the sample liquefy, because that too bears on the counts.
Reference value
Described, not measured
What it measures
How readily the liquefied sample forms a thread when drawn up and released. It is graded rather than measured.
What it does and does not tell you
Often confused with liquefaction, which is a different property: a sample can liquefy promptly and still be viscous. High viscosity hampers accurate counting and can trap motile spermatozoa, so like delayed liquefaction it can lower figures for reasons that have nothing to do with sperm production.
Reference value
7.2 or more
Lower limit — results at or above it are unremarkable
Source: WHO laboratory manual
What it measures
How acidic or alkaline the sample is, measured once it has liquefied. What it registers is the mix of fluids making up the ejaculate, rather than anything about the spermatozoa carried in them.
What it does and does not tell you
Seminal vesicle fluid is alkaline and prostatic fluid is acidic, so the pH reflects the balance between them. On its own it says very little. It earns its place in combination: a low pH alongside a low volume and no spermatozoa raises the possibility that the seminal vesicle contribution is missing, which happens where the vasa and vesicles have not formed normally. A normal pH with a normal volume makes that particular pattern unlikely — one of the few places on the report where a single unremarkable figure genuinely narrows the field.
Reference value
54% or more%
Lower limit — results at or above it are unremarkable
Source: WHO 6th edition (2021)
What it measures
The proportion of spermatozoa that are alive, shown by a dye that enters only cells whose membrane has broken down: living sperm stay unstained.
What it does and does not tell you
It matters most when motility is low. Spermatozoa that are immotile but alive point towards a problem with the machinery of movement in the tail; immotile and dead points towards something affecting survival. The figure also serves as an internal check, since vitality cannot honestly fall below total motility.
Reference value
Counted first, then identified as the line below
What it measures
Cells in the sample that are not spermatozoa, counted together before being identified. They include immature sperm precursors and white blood cells, which look alike under a plain microscope.
What it does and does not tell you
The count alone does not separate the two, and that separation is the entire point: immature germ cells are an ordinary finding, whereas white blood cells above the threshold raise a different question. A raised round cell count therefore leads to the stain reported on the line below rather than to a conclusion.
Finer readings of this same line
Reference value
Under 1 million/mLmillion/mL
Upper limit — results at or below it are unremarkable
Source: WHO laboratory manual
What it measures
White blood cells specifically, distinguished from the other round cells by a stain that reacts with the peroxidase enzyme they carry.
What it does and does not tell you
A ceiling, not a floor: a low figure is the unremarkable one, and reading this line as though it had a minimum turns an ordinary result into an alarming one. Above the threshold the finding is called leucocytospermia. It does not by itself mean infection, since inflammation without infection produces the same picture, so it opens a question rather than answering one.
Reference value
Graded, not measured
What it measures
Motile spermatozoa sticking to one another — head to head, tail to tail, or mixed. Sticking to debris or to non-motile cells is a different thing, called aggregation.
What it does and does not tell you
Agglutination of motile spermatozoa is the finding that carries weight, because antisperm antibodies are one of its causes. Its presence is among the reasons the antibody tests further down the report are requested; its absence does not rule them out. It is graded and described rather than given a number.
Reference value
Reported only when no sperm are seen initially
What it measures
Where no spermatozoa are seen on the routine examination, the sample is spun at high speed and the pellet at the bottom examined. This line records what that showed.
What it does and does not tell you
It is the step that separates two different findings. None anywhere, confirmed on a second sample, is azoospermia. A very small number found only in the pellet is cryptozoospermia, and is a different conversation with different options. Azoospermia reported without the pellet having been examined, or from a single sample, is the commonest way this finding is got wrong.
On a fertility clinic report
Added when the question has moved past whether sperm are present and moving.
Reference value
Measured by one of the tests below
What it measures
Antibodies bound to the surface of a man’s own spermatozoa, measured by one of the tests below rather than directly.
What it does and does not tell you
The blood–testis barrier normally keeps spermatozoa away from the immune system. Where that barrier has been breached — by surgery, injury, torsion or infection — antibodies can form against them. Bound antibodies can impair movement through cervical mucus and binding to the egg. The tests are usually requested where motility is low, where agglutination is seen, or where the history includes such an event.
Finer readings of this same line
Reference value
Under 50% of motile sperm with bound particles%
Upper limit — results at or below it are unremarkable
Source: WHO laboratory manual
What it measures
The mixed antiglobulin reaction: coated particles are added to the fresh sample, and the proportion of motile spermatozoa that pick them up is counted.
What it does and does not tell you
An upper limit, so a low percentage is the unremarkable result. It is quick and runs on the untreated sample, which is why it is the more commonly offered of the two. Where antibodies coat only part of the sperm surface, the site of binding — head or tail — is reported as well, since it bears on how the antibodies would interfere.
Reference value
Under 50% of motile sperm with bound beads%
Upper limit — results at or below it are unremarkable
Source: WHO laboratory manual
What it measures
The same question asked with beads carrying antibodies against particular classes of human immunoglobulin, run on washed spermatozoa.
What it does and does not tell you
Slower and more demanding than the MAR test, and more specific: it names which class of antibody is bound and where. The two are alternatives rather than a sequence, and a laboratory generally offers one or the other.
Reference value
No WHO reference limit for the indices
What it measures
A breakdown of the abnormal forms rather than a single percentage: which part of the spermatozoon is affected, and how many defects the average abnormal one carries. The teratozoospermia index is that average.
What it does and does not tell you
Useful mainly as a pattern. Defects concentrated in one structure — almost all heads, or almost all tails — can point towards a specific cause, where a scatter across all three usually does not. The indices carry no WHO reference limit and are reported against each laboratory’s own experience, so figures from two laboratories are not directly comparable.
Reference value
Reported against each laboratory’s own range
What it measures
The hypo-osmotic swelling test: spermatozoa are placed in a dilute solution, and those with an intact membrane take up water and curl their tails.
What it does and does not tell you
Another way of asking the vitality question, for occasions when the staining method is unsuitable — including when the spermatozoa are to be used afterwards, since the dyes kill them and this does not. It is reported as a percentage of swollen forms against each laboratory’s own range.
Specialist and add-on tests
Ordered for a specific question, usually separately from the semen analysis itself.
Reference value
No agreed threshold; it differs by assay and by laboratory
What it measures
The proportion of spermatozoa carrying breaks in their DNA strands. Several assays measure it — SCSA, TUNEL, the sperm chromatin dispersion or Halosperm test, and the Comet assay — and they measure related but not identical things.
What it does and does not tell you
An ordinary semen analysis says nothing about this, which is the argument for the test. Against it: the assays are not interchangeable, the cut-offs quoted are specific to each one, and no single threshold is agreed, which is why no figure appears in the reference column. Its place in practice is contested rather than settled, and a percentage carries meaning only alongside the assay that produced it and that laboratory’s own range.
Reference value
No agreed threshold
What it measures
A measure of the balance between reactive oxygen species in the sample and the antioxidant capacity holding them in check, reported by several methods including a direct oxidation–reduction potential.
What it does and does not tell you
Some reactive oxygen is necessary for spermatozoa to function; an excess damages membranes and DNA, which is why this and the fragmentation test are often discussed together. As with fragmentation, the methods differ, no threshold is agreed, and a number means little without the method and range that produced it.
Reference value
Reported as the separate markers below
What it measures
Markers of the individual glands that contribute to the ejaculate, each one standing for a different part of the tract.
What it does and does not tell you
The purpose of measuring them is anatomical rather than functional: each marker comes from a known source, so a missing marker localises where the problem lies. They are requested chiefly where the volume is low or where no spermatozoa are found, and rarely otherwise.
Finer readings of this same line
Reference value
Read as present or absent, against the laboratory’s own range
What it measures
A sugar made by the seminal vesicles and used by spermatozoa as fuel. Its presence stands for the seminal vesicles having contributed to the ejaculate.
What it does and does not tell you
Absent fructose alongside a low volume and an acid pH is the pattern that raises the possibility of absent or obstructed seminal vesicles and vasa. Where the volume and pH are unremarkable it adds little, which is why it forms no part of a routine analysis.
Reference value
Read as present or absent, against the laboratory’s own range
What it measures
An enzyme produced by the epididymis, the coiled duct where spermatozoa mature and are stored. Its presence stands for the epididymis having contributed.
What it does and does not tell you
The marker that speaks to obstruction between the testis and the vas. A low level alongside no spermatozoa shifts the picture towards a blockage at that level rather than a failure of production — though no single marker settles that question on its own.
Reference value
Read as present or absent, against the laboratory’s own range
What it measures
A mineral concentrated in prostatic fluid, standing for the prostate’s contribution to the ejaculate.
What it does and does not tell you
Read as a marker of where the fluid came from rather than as a nutritional measurement: a low seminal zinc says nothing about zinc in the diet or in the blood. Like the other two markers it is informative mainly where a gland’s contribution appears to be missing altogether.
Reference value
Reported against each laboratory’s control range
What it measures
Fluorescent probes are used to count copies of selected chromosomes inside individual spermatozoa, and the proportion carrying the wrong number is reported.
What it does and does not tell you
Every man produces some chromosomally abnormal spermatozoa; the question this asks is whether the proportion is unusually high. It is reported against each laboratory’s control range rather than a universal threshold, and it belongs to specific situations — recurrent pregnancy loss, repeated unsuccessful cycles, or a known chromosomal finding — rather than to a general assessment.
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