What a semen analysis really means

A semen analysis is the first (and most important) lab test used to assess male fertility—but it’s easy to misread. It’s not a pass/fail exam, and a normal result doesn’t guarantee pregnancy, just as an abnormal result doesn’t mean you can’t conceive. Major guidelines emphasize that semen parameters sit on a continuum and vary from sample to sample.

1) What a semen analysis can and cannot tell you

A semen analysis estimates:

• how much semen is produced (volume),

• how many sperm are present (concentration and total sperm number),

• how many sperm are moving (motility),

• and how many look “normally shaped” (morphology).

But here’s the key: the reference limits commonly shown on reports come from men whose partners conceived within 12 months—so the lower values represent the lower end of the fertile range, not a boundary between fertile and infertile.

Guidelines also stress high natural variability between ejaculates, so if anything is abnormal, it’s usually worth repeating the test in about 6 weeks.

2) Getting the test right

Common guideline-based collection standards include:

• 2–7 days abstinence before collection

• Ideally provide the sample on-site; otherwise get it to the lab within ~1 hour, avoiding heat/cold exposure

• If the first test is abnormal, repeat

Even simple factors like fever in the prior 2–3 months, new medications, heavy alcohol use, anabolic steroids/testosterone, or sample delay can shift results.

3) Volume (mL): what it means

What it is: the total fluid volume ejaculated.

Why it matters: volume affects the total number of sperm delivered, and very low volume can be a clue to:

• incomplete collection,

• very short abstinence,

• retrograde ejaculation,

• ejaculatory duct obstruction,

• or absent/underdeveloped seminal vesicles/vas deferens.

WHO 2021 (6th ed.) reference value: ~1.4 mL.

Practical takeaway: Mildly low volume is often a collection/abstinence issue. Persistently low volume—especially with acidic pH or very low sperm—may warrant medical review.

4) Count: concentration vs total sperm number

A) Sperm concentration (million/mL)

What it is: sperm per millilitre.

WHO 2021 ~16 million/mL.

B) Total sperm number (million per ejaculate)

What it is: concentration × volume—the total sperm in the entire sample.

Why it often matters more: total sperm number is a better reflection of total sperm production and delivery than concentration alone (because concentration can look okay in a tiny volume, or low in a very large volume).

WHO 2021 ~39 million per ejaculate.

Practical takeaway: If you want one count number to focus on, look at total sperm number.

5) Motility

Motility is typically divided into:

• Progressive motility (PR): moving forward

• Non-progressive (NP): moving but not forward effectively

• Immotile (IM): not moving

WHO 2021 5th centile values:

• Total motility (PR + NP): ~42%

• Progressive motility (PR): ~30%

Total Motile Sperm Count (TMSC)

TMSC combines the key ingredients:

TMSC = volume × concentration × total motility

Why this matters: multiple studies and reviews show TMSC correlates with chances of pregnancy—especially in natural conception and with intrauterine insemination (IUI).

• In a large IUI analysis, pregnancy rates were highest around TMSC ≥ ~9 million, with a gradual decline below that.

• Reviews of IUI outcomes often cite better success when total motile count is above a few million (exact thresholds vary by study and lab methods).

6) Morphology

What it is: the percentage of sperm that meet strict shape criteria (head, midpiece, tail). Because sperm vary widely and scoring is technique-dependent, morphology has more measurement variability than people expect.

WHO 2021 ~4% (strict criteria).

Is low morphology a big problem?

Sometimes—but often not by itself.

In IUI populations, several studies have found that morphology alone (e.g., <4%) is not a reliable standalone predictor of pregnancy outcomes, and that motile sperm counts are often more predictive.
Recent reviews also emphasize that morphology’s clinical relevance depends heavily on context (other semen parameters, female partner factors, and the treatment being used).

When morphology may matter more:

• when it is severely low and paired with low count/motility,

• when there is a suspected specific defect pattern (e.g., rare syndromic forms),

• when deciding between conventional IVF vs ICSI in certain settings.

Practical takeaway: Morphology is a piece of the puzzle, but it’s rarely the most important piece.

7) What to do with borderline or abnormal results

Recommend:

• Don’t panic over one result—because variability is real.

• If abnormal, repeat the semen analysis (often ~6 weeks apart).

• If abnormalities persist, see a clinician experienced in male fertility for history, exam, and targeted tests

• Routine add-ons like sperm DNA fragmentation are not recommended as first-line for everyone but can be added on later when indicated.