Sperm & semen · In plain English

Semen liquefaction and viscosity

Liquefaction describes semen becoming more fluid after ejaculation. Viscosity describes how thick or stringy the sample remains.

Also searched as: thick semen, liquefaction time, semen viscosity

Why you might see this term

These are laboratory observations of the fluid, separate from sperm numbers, shape and movement. They can help explain practical difficulties in assessing a sample.

What to keep in mind

Appearance at home cannot reliably identify the cause of an unusual finding. Follow collection instructions and discuss persistent concerns.

Sources & further reading

Prepared by ProFertility · Updated 23 October 2026.

Educational information based on the linked sources. This explanation is not an individual diagnosis or a treatment recommendation. A term appearing here does not mean the test is necessary or included in a particular kit.

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