Lab marker · Low

Low Progesterone (P4): what it means

A Progesterone (P4) result below the normal range is considered low. Here is what a reduced Progesterone (P4) can point to, and when it is worth discussing with a doctor.

Reference range: Follicular <1, luteal 3–25 (>3 confirms ovulation); rises into the hundreds in pregnancy; post-menopause <0.5 ng/mL

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What a low Progesterone (P4) can mean

  • Anovulation — no ovulation, so no corpus luteum; the commonest cause of a low day-21 value (seen in PCOS, thyroid disease, hyperprolactinaemia, hypothalamic amenorrhoea).
  • Luteal phase deficiency — corpus luteum forms but underperforms.
  • Menopause / ovarian insufficiency.
  • Wrong test timing — a level drawn too early or in an irregular cycle looks falsely low; the day-21 assumption fails when cycles aren't 28 days.

When to discuss with a doctor

The single most useful use of progesterone is a mid-luteal draw to confirm ovulation — timed 7 days before the expected next period, not blindly on day 21, because that assumption breaks with irregular cycles. A value >3 ng/mL means you ovulated; a low value in a woman trying to conceive prompts the anovulation work-up (thyroid, prolactin, androgens, PCOS assessment). Very high progesterone in a non-pregnant woman with virilisation should prompt evaluation for congenital adrenal hyperplasia. Mediora.AI shows progesterone alongside its cycle timing and companion hormones; the fertility interpretation belongs with your gynaecologist or fertility specialist.

Conditions this can relate to

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Mediora.AI is informational - interpretation, not a diagnosis. A single out-of-range value is common and often benign; always discuss decisions with your doctor.