What it measures
- Progesterone
Who it’s for
- Trying to conceive and wanting to confirm ovulation
- Irregular cycles
- Fertility investigations
Why timing is everything
After you ovulate, the empty follicle makes progesterone to prepare your womb for pregnancy. Levels peak about a week after ovulation, so the test is timed around seven days before your next period. That’s day 21 of a 28-day cycle, but day 28 of a 35-day cycle. Testing on the wrong day is the most common reason for a misleadingly low result.
Understanding your result
A clearly raised progesterone confirms you ovulated that cycle. A low result may mean you didn’t ovulate, or that the test was taken at the wrong time. One cycle can differ from the next, so if your result is low your doctor may suggest testing again.
How to prepare
- 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.
- Drink a couple of glasses of water beforehand: it makes the sample quicker and easier to take.
- No fasting needed. Eat and drink as normal.
When should I book?
How it works at our Croydon clinic
Book online
Choose your test and a time that suits you. No GP referral needed.
A 15-minute visit
A trained clinician takes a small blood sample at 169 Shirley Road, Croydon. Tell us if you’re nervous.
Results in 1–3 days
A clear report showing each result against its reference range.
Next steps
Share your report with your GP, who can arrange NHS follow-up if anything needs it.
Questions
My cycle isn’t 28 days. When do I test?
Count back seven days from when you expect your next period. The date helper on this page works it out for you.
Can I test if my periods are irregular?
Yes, but timing is harder. You may need more than one test, a week apart, until your period arrives.
How much is a Day 21 Progesterone in Croydon?
£55 at our clinic at 169 Shirley Road, Croydon, including taking your blood sample and your report.
How quickly will I get my results?
Usually within 1 to 3 days, in a clear report showing each result against its reference range.