What it measures
- Progesterone
How progesterone confirms ovulation
After you ovulate, the empty follicle produces progesterone to prepare the womb lining for pregnancy. Progesterone peaks about a week after ovulation, so a blood test at that point shows whether ovulation happened.
Timing your test
Count back 7 days from when you expect your next period. In a 28-day cycle that’s day 21; in a 35-day cycle, day 28. If your cycles vary, testing more than once may be needed. A low result in one cycle doesn’t always mean a problem, as occasional cycles without ovulation are normal.
Who it’s for
- Trying to conceive and wanting to confirm ovulation
- Irregular cycles
- Fertility investigations
How to prepare
- Drink plenty of water beforehand; it makes the sample quicker and easier to take.
- You don’t need to fast.
- Book for about 7 days before your next period is due: day 21 of a 28-day cycle, or day 28 of a 35-day cycle.
Progesterone Blood Test: your questions
What is a good day 21 progesterone level?
A level above about 30 nmol/L is generally taken to show ovulation, although laboratories use slightly different ranges. Your report will show your result against its range.
Information on this page is general and doesn’t replace advice from your GP, midwife or consultant. If you feel unwell or are worried about symptoms, contact your GP, call NHS 111 or, in an emergency, 999.