What Is Progesterone?
Progesterone is a sex hormone produced mainly by the corpus luteum after ovulation, and by the placenta during pregnancy. It prepares the uterus for implantation, maintains early pregnancy, and regulates the menstrual cycle.
Normal Progesterone Levels
| Phase / Situation | Normal Progesterone (ng/mL) |
|---|---|
| Follicular phase (pre-ovulation) | 0.1–0.9 |
| Ovulation | Starts rising above 1.0 |
| Mid-luteal phase (7 days post-ovulation) | 5–20 (ideally >10 confirms ovulation) |
| Post-menopause | Below 0.5 |
| Pregnancy — 1st trimester | 11–90 |
| Pregnancy — 2nd trimester | 25–90 |
| Pregnancy — 3rd trimester | 48–300 |
What Low Progesterone Means
- No ovulation occurred (anovulation) — common in PCOS
- Luteal phase defect — corpus luteum not producing enough
- Early miscarriage or threatened miscarriage
- Ectopic pregnancy
What High Progesterone Means
- Pregnancy (expected and normal)
- Ovarian cysts
- Congenital adrenal hyperplasia
- Certain ovarian tumours
Progesterone and Fertility
A mid-luteal progesterone above 5 ng/mL (and ideally above 10 ng/mL) confirms that ovulation occurred. This is a key fertility test for women with irregular periods or difficulty conceiving.
FAQs
When should the progesterone test be done?
For fertility: 7 days before your expected next period (mid-luteal phase). Cycle day 21 is used in a standard 28-day cycle.
Can progesterone supplements be prescribed for low levels?
Yes — vaginal progesterone or oral forms are often prescribed in early pregnancy or fertility treatment.
Does stress affect progesterone?
Chronic stress raises cortisol, which can suppress progesterone production.
Medical Disclaimer: Progesterone levels must be interpreted relative to the day of your menstrual cycle. Always discuss results with your doctor or gynaecologist.