What it measures
The share of sperm that are alive, judged with a stain that only enters dead cells. It is read when many sperm are not moving, to tell live but still sperm from dead ones.
Why people test it
- Checked by couples who have been trying for a baby for a while.
- Part of a semen analysis, read alongside count, movement and shape.
Typical range
Reported as a percentage of the sperm counted. Labs usually compare it with World Health Organization reference values; ranges vary by lab, and the report shows the lab's own.
Finger-prick or vein?
A semen sample rather than blood, produced at home into the pot from the kit and posted to the lab. Sperm change with time and temperature once the sample is produced, so the kit's timing instructions matter.
Labs ask for a set number of days without ejaculation before the sample, as this affects the result; the kit instructions give the window.