Sperm health
Sperm morphology
Normal sperm morphology has a lower reference limit of 4% on strict criteria. That is a reference limit, not a mark out of 100.
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Short answer
Sperm morphology is the percentage of sperm with a normal shape. Using the WHO strict criteria cited by NICE, 4% or more normal forms is within the current reference range. A lower percentage is below the current reference value. Most sperm are not classified as normal even when the result is inside the reference range.
Key takeaways
- 4% is a lower limit, not a poor grade.
- Strict criteria look at the head, midpiece and tail.
- Morphology is more variable between laboratories than a simple count.
- A low percentage is described as teratozoospermia. It still is not a fertility verdict.
| Measurement | Reference value | How to read it |
|---|---|---|
| Semen volume | 1.4 ml or more | Within the current reference range at or above this value |
| Sperm concentration | 16 million/ml or more | Within the current reference range at or above this value |
| Total sperm number | 39 million or more | Within the current reference range at or above this value |
| Total motility | 42 % or more | Within the current reference range at or above this value |
| Progressive motility | 30 % or more | Within the current reference range at or above this value |
| Vitality | 54 % or more | Within the current reference range at or above this value |
| Normal morphology | 4 % or more | Within the current reference range at or above this value |
NICE also cites semen pH of 7.2 or more. These are lower reference limits, not a fertility diagnosis.
What “normal forms” means
The assessor compares each sperm with a strict definition of a normal head, midpiece and tail. Borderline shapes are not counted as normal. That is why the reference limit sits at 4% rather than a number that looks like a majority. If a report from an older method says 30% normal, it may not be using the same criteria. Do not compare it with 4%.
A result under 4%
Teratozoospermia means the proportion of normal forms is below the reference limit. Clinics differ in how heavily they weight morphology next to count and motility. NICE includes morphology in the semen analysis comparison and does not treat it as a standalone diagnosis. An abnormal analysis is confirmed, usually after about three months, unless there is a gross sperm deficiency.
Limits of the measurement
Morphology scoring has a human component. Two laboratories can differ. A single low result after a fever, or from a sample that was poorly smeared, is a weak basis for a long-term label. It is also a weak basis for buying a supplement aimed at “shape”. The morphology evidence page explains how little pregnancy outcome data sits behind that idea.
Related
Sources
- WHO laboratory manual for the examination and processing of human semen, 6th edition — World Health Organization, 2021
- Fertility problems: assessment and treatment (NG257) — NICE, 2026
- NG257: investigation of fertility problems and management strategies — NICE, 2026
- Low sperm count — NHS
How this page was prepared
Drafted with automated research assistance and checked against the cited primary sources. A named clinician has not reviewed this page. Medical review is pending. Changes to reference values are not published automatically.