What this test measures
Progesterone is produced by the corpus luteum after ovulation (and by the placenta in pregnancy). It prepares the endometrium for implantation and maintains it once a pregnancy is established. In the absence of ovulation, progesterone stays low.
The serum assay measures total progesterone. The single most useful clinical sample is taken roughly 7 days before the expected period — usually cycle day 21 in a 28-day cycle, adjusted for cycle length — to confirm ovulation. In early pregnancy, progesterone is measured to assess viability.
Why it matters
A mid-luteal progesterone > 10 ng/mL confirms that ovulation has occurred, which is one of the first questions in any subfertility workup. A persistently low mid-luteal progesterone with irregular cycles is the typical pattern in PCOS and anovulatory cycles — the cause of around 25% of female infertility.
In early pregnancy, a low progesterone (< 5 ng/mL) strongly predicts a non-viable pregnancy (miscarriage or ectopic). Progesterone is also routinely used to support luteal phase in IVF cycles, in some recurrent miscarriage protocols, and in the workup of unscheduled bleeding to assess endometrial response.
How to prepare
No fasting required. For ovulation confirmation, draw exactly 7 days before the expected period (cycle day 21 in a 28-day cycle, day 25 in a 32-day cycle, etc.). For an irregular cycle, your doctor may suggest serial weekly samples or pair with ultrasound. Stop biotin for 48–72 hours. Tell the lab about progesterone supplements (vaginal, oral or injectable) — they raise the level.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Progesterone (ng/mL)[1][2] | Follicular: < 1.0 · Mid-luteal: > 10 (ovulatory) · 1st trimester: 11.2 – 90.0 · Postmenopausal: < 0.2 | Mid-luteal progesterone < 3 ng/mL = anovulation. 3–10 ng/mL = inadequate luteal phase or wrong timing of the draw. In early pregnancy < 5 ng/mL strongly suggests a non-viable pregnancy. | Raised progesterone in the follicular phase suggests luteinised unruptured follicle, ovarian cyst or rare ovarian tumour. Very high progesterone is normal in pregnancy — rising substantially through each trimester. |
Progesterone — interpretation by setting
| Setting | Progesterone (ng/mL) | Interpretation |
|---|---|---|
| Mid-luteal (day 21) | > 10 | Ovulation confirmed |
| Mid-luteal (day 21) | 3 – 10 | Possible luteal phase defect or wrong timing |
| Mid-luteal (day 21) | < 3 | Anovulation |
| Early pregnancy (5–8 weeks) | > 25 | Likely viable intrauterine pregnancy |
| Early pregnancy | 5 – 25 | Indeterminate — needs serial β-hCG + ultrasound |
| Early pregnancy | < 5 | Non-viable pregnancy or ectopic |
| Postmenopausal | < 0.2 | Normal |
Frequently asked questions
When in my cycle should progesterone be checked?
For ovulation confirmation, exactly 7 days before the expected period (day 21 in a 28-day cycle, day 25 in a 32-day cycle). Drawing on a fixed "day 21" when your cycle is not 28 days is one of the most common reasons for misleading low results.
My day-21 progesterone is low — am I not ovulating?
Possibly — or the timing was off. If your cycle is longer than 28 days, day 21 is before ovulation. Recheck 7 days before your next expected period, or have weekly samples until your period arrives.
Should I take progesterone supplements if it is low?
Not on a single result. Routine progesterone supplementation for luteal phase support outside IVF is controversial. RCOG supports vaginal progesterone in early pregnancy in women with bleeding and prior miscarriage. Discuss with your gynaecologist.
My early-pregnancy progesterone is low — does that mean miscarriage?
A progesterone below 5 ng/mL strongly predicts non-viable pregnancy (either miscarriage or ectopic). A single low value is not 100% diagnostic — serial β-hCG and an early ultrasound are usually the next steps.
Will birth control pills affect progesterone?
Yes — combined oral contraceptive pills suppress ovulation, so progesterone stays low through the cycle. Stop for 3 months for a meaningful natural cycle measurement.
Why is progesterone tested in PCOS workup?
A persistently low mid-luteal progesterone over multiple cycles documents the anovulation that defines PCOS, alongside ultrasound and androgen testing.
Can stress lower progesterone?
Acute and chronic stress can suppress the hypothalamic-pituitary axis, lower LH, and prevent ovulation — which then keeps progesterone low. Lifestyle factors matter.
Related Hormones / Endocrine tests
Tests commonly ordered alongside PROGESTERONE, or that help interpret an unexpected result.
Sources & references
- ASRM — Diagnostic Evaluation of the Infertile Female · accessed 2026-05-30T00:00:00.000Z
- RCOG — Recurrent Miscarriage Guideline · accessed 2026-05-30T00:00:00.000Z
- NIH MedlinePlus — Progesterone Test · accessed 2026-05-30T00:00:00.000Z
- NCBI StatPearls — Progesterone · accessed 2026-05-30T00:00:00.000Z
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