Day-21 Progesterone Test
A blood test taken about a week before your period to check whether you've ovulated.
Quick Summary
To confirm ovulation when investigating infertility.
Progesterone level in the second half of the cycle.
Timed about 7 days before your expected period (day 21 of a 28-day cycle).
Overview
Timing depends on your cycle length.
A rise in progesterone shows ovulation happened.
What It Measures
Progesterone
Hormone level.
How It's Performed
- 01
Preparation
Usually no special preparation unless your doctor advises.
- 02
Blood sample
A small amount of blood is taken from a vein in your arm.
- 03
Afterwards
Press on the spot; a small bruise is common.
Interpreting Results & Next Steps
Discuss with Doctor
Normal ranges differ between laboratories; use the range on your report. Your doctor will explain what your result means and what happens next.
If values are Low:
Low levels may mean ovulation didn't happen that cycle.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- Progesterone Test(opens in a new tab) · MedlinePlus, US National Library of Medicine