How to Read a Semen Analysis and the WHO Reference Limits

A semen analysis measures the ejaculate, not fertility as a whole. It can identify patterns that make conception less likely or point to obstruction, impaired production, ejaculation problems, infection, or endocrine and genetic conditions. It cannot by itself predict whether a couple will conceive, because results vary and reproductive outcomes depend on both partners, timing, sexual function, age, tubal and ovulatory factors, and chance.

Start with how the sample was produced#

Pre-analytic details can change nearly every result. Your report should state abstinence interval, collection method, whether the complete ejaculate entered the container, time from collection to analysis, and any difficulty.

The first fraction often contains a high concentration of sperm. Losing it can give you an artificially low count and volume. A standard non-toxic container is important; ordinary lubricants and condoms can impair motility unless specifically designed for semen collection.

WHO procedures commonly standardize an abstinence interval of two to seven days for diagnostic sampling. A longer interval can increase volume or count while reducing motility or changing other features; a short interval can do the reverse. The exact interval should be recorded rather than judged morally.

Analysis should begin promptly under controlled conditions because motility changes with time and temperature. A home-collected sample may be acceptable if the laboratory provides and validates instructions; fever in the previous several months, acute illness, medicines, and recent genitourinary events can influence results because sperm production and maturation take weeks.

The reference population defines the numbers#

The WHO sixth edition expanded reference data to thousands of men across several continents whose partners achieved natural conception within 12 months. The lower reference limit is the fifth centile: about 5% of this selected fertile reference group had a result below it.

That design has two consequences. First, values below a limit can occur in proven fertile men. Second, values above a limit can occur in an infertile couple. The reference group does not represent every age, region, health condition, or time-to-pregnancy experience equally; WHO emphasizes standardized laboratory methods and interpretation of the whole distribution, and the sixth edition does not endorse turning one lower centile into a universal fertility decision limit.

The commonly reported lower fifth centiles#

The 2021 reference distribution includes approximate lower limits, with laboratory units checked carefully:

• semen volume: 1.4 mL;
• total sperm number: 39 million per ejaculate;
• sperm concentration: 16 million per mL;
• total motility, progressive plus nonprogressive: 42%;
• progressive motility: 30%;
• vitality, live sperm: 54%;
• normal morphology using strict criteria: 4%.

The WHO source also gives confidence intervals around these centiles. A report that hands you only a rounded boundary hides that statistical uncertainty and the ordinary within-person variability. Laboratories may use validated local reference data or terminology and should state the method. Compare your result with the correct edition and technique, not with an internet table from another laboratory.

Volume and total number answer different questions#

Semen volume comes mainly from seminal vesicles and prostate, not the testis. Low volume can reflect incomplete collection, short abstinence, retrograde ejaculation, ejaculatory-duct obstruction, absent or abnormal seminal vesicles, low androgen state, or other conditions. High volume can dilute concentration without increasing total sperm.

Concentration is sperm per milliliter. Total sperm number is concentration multiplied by volume. A concentration of 20 million/mL in 1 mL yields 20 million total; 12 million/mL in 4 mL yields 48 million total. The first is above the concentration reference but below the total-number reference; the second is the reverse. Very low volume with azoospermia and acidic pH can suggest an obstructive or ejaculatory pattern that needs targeted evaluation. It is not diagnosed by volume alone.

Motility has direction and timing#

Progressive motility means sperm move actively forward. Nonprogressive sperm move without meaningful advancement. Immotile sperm do not move during assessment. Total motility combines progressive and nonprogressive categories.

Motility depends on timely analysis, temperature, specimen toxicity, and observer or computer method. A low motility percentage can arise because sperm are dead or because live sperm are not moving. Vitality testing helps distinguish those situations, especially when many sperm are immotile.

Total motile sperm count is often estimated as volume times concentration times the motile fraction, sometimes using progressive motility specifically, and it can inform counseling and treatment planning, but cutoffs vary by clinical context and laboratory and do not guarantee pregnancy.

Morphology is often misunderstood#

Strict morphology classifies sperm as normal only when head, midpiece, and tail meet a narrow visual standard. If your report says 4% normal forms, it means 4 of 100 assessed sperm met every criterion. It does not mean the remaining 96% cannot fertilize, carry abnormal chromosomes, or are “defective babies.”

Morphology assessment has substantial laboratory and observer variability. Its independent ability to predict natural conception or assisted-reproduction outcome is limited, especially near the boundary, and an isolated morphology result should not drive a major intervention without the full reproductive context. The report should state the classification system, number assessed, quality control, and whether special patterns such as complete globozoospermia are suspected. Rare uniform defects can carry more diagnostic significance than a modestly low percentage.

Other report elements#

Liquefaction, viscosity, appearance, pH, agglutination, round cells, and debris can affect analysis or suggest a need for further work. “Round cells” may be white blood cells or immature germ cells; additional testing distinguishes them.

The WHO/EAU consensus threshold for peroxidase-positive leukocytes is below 1 million/mL, but leukocytospermia does not by itself prove bacterial infection. Symptoms, examination, culture strategy, and other findings guide evaluation. Empiric antibiotics solely to improve a number can cause harm and may not improve pregnancy outcomes.

Antisperm antibody and sperm DNA fragmentation tests are not routine additions for every initial analysis. Guidelines reserve advanced tests for selected situations because methods, thresholds, and impact on management differ.

Azoospermia needs confirmation and classification#

Azoospermia means no sperm found in the ejaculate after appropriate examination, including evaluation of a centrifuged pellet under validated laboratory procedures, and it should be confirmed because rare sperm may be missed and collection can be incomplete.

The next question is whether sperm production is impaired or sperm are produced but blocked from reaching the ejaculate. History, physical examination, semen volume and pH, follicle-stimulating hormone and testosterone, testicular size, prior surgery or infection, and genetic testing in indicated severe cases help distinguish patterns.

Exogenous testosterone and anabolic steroids can suppress sperm production, sometimes profoundly. People seeking current or future fertility should not start or stop hormones without expert guidance. Recovery timing varies.

Repeat testing addresses biological variation#

Semen parameters vary from ejaculate to ejaculate. AUA/ASRM guidance notes that at least two analyses, ideally at least a month apart, are important when the first is abnormal. The interval may be adjusted for an urgent fertility timeline, recent fever, treatment, or suspected azoospermia.

Repeat testing is useful only if collection and laboratory conditions are documented and reasonably comparable. Endless repetition without clinical evaluation delays diagnosis. A single clearly severe result, palpable testicular mass, endocrine symptoms, or a history of gonadotoxic therapy warrants prompt assessment while confirmation proceeds.

Interpret the person and couple, not just the table#

Initial evaluation includes reproductive and sexual history, puberty, childhood testicular position, infection, injury, surgery, cancer therapy, medicines, heat and toxin history, family history, prior pregnancies, and physical examination. Both partners should be assessed concurrently because delay can matter, particularly with increasing female partner age.

Seeking evaluation is generally appropriate after 12 months of regular unprotected intercourse without conception, earlier when the female partner is 35 or older or either partner has a known risk factor. Recurrent pregnancy loss and failed assisted-reproduction cycles can also prompt male evaluation.

Lifestyle measures should focus on health and proven harms: stop tobacco and nonprescribed anabolic steroids, avoid excessive alcohol or drugs, address obesity and sleep where relevant, and review occupational heat or toxins. Evidence for antioxidant supplements is uncertain, products vary, and more is not necessarily safe.

A practical reading sequence#

Confirm identity, laboratory, date, abstinence interval, complete collection, and processing time. Read volume, concentration, total number, progressive and total motility, vitality, and morphology together. Note round cells and technical comments.

Compare with the correct WHO reference distribution without labeling fertility. Look at your previous samples, recent illness, medicines, and partner factors. If abnormal, plan appropriately timed confirmation and specialist evaluation rather than diagnosing from one parameter.