Progesterone Levels During Menstruation
Yes, progesterone levels are dramatically affected when you're on your period—they drop to their lowest point (<1 ng/mL) during menstruation and remain low throughout the early follicular phase.
Normal Menstrual Cycle Progesterone Pattern
During a typical menstrual cycle, progesterone follows a predictable pattern 1:
- Menstruation (Days 1-5): Progesterone levels are at their nadir, typically <1 ng/mL 2
- Follicular phase (Days 1-14): Progesterone remains low while estrogen rises
- Ovulation: Brief hormonal surge occurs with falling estrogen
- Luteal phase (Days 14-28): Progesterone rises significantly, peaking at mid-luteal phase
- Pre-menstrual: Both progesterone and estrogen fall, triggering menstruation
Clinical Interpretation
When interpreting progesterone levels diagnostically, timing relative to menstruation is absolutely critical 2. The Endocrine Society guidelines specify that:
- Progesterone <1 ng/mL during menstruation is completely normal
- Elevated FSH and LH with progesterone <1 ng/mL and low estradiol (<20 pg/mL) indicates ovarian insufficiency
- Progesterone <2 ng/mL with high FSH/LH and estradiol >150 pg/mL suggests midcycle gonadotropin surge
Important Caveats
Residual progesterone secretion can occasionally persist into early menstruation, particularly in cycles with luteal phase follicular waves 3. Recent evidence shows that:
- Persistent progesterone during the first week of menstruation (PDG levels 1.5-4 µg/mg creatinine) can delay the onset of the fertile window
- This residual secretion may be supported by subtly elevated LH during the perimenstrual period
- Such persistence is the exception rather than the rule
Practical Testing Implications
If you're testing progesterone levels to assess ovulation or luteal function, never draw blood during menstruation—the results will be uninterpretable as levels should be low. Optimal timing for progesterone testing is:
- Mid-luteal phase (approximately day 21 of a 28-day cycle, or 7 days post-ovulation)
- This captures peak progesterone production from the corpus luteum
- Levels >3-5 ng/mL confirm ovulation occurred
Testing during menstruation will only confirm that progesterone appropriately dropped to trigger endometrial shedding, providing no useful diagnostic information about ovulatory function 2, 1.