Progesterone
What This Test Measures
Measures serum progesterone levels. Used to confirm ovulation, evaluate luteal phase function, and monitor progesterone supplementation. Important note: if you take oral micronized progesterone (e.g. Prometrium), standard immunoassay results will appear significantly elevated and do not accurately reflect tissue levels — this is a known limitation of the test method. Women on oral progesterone who need clinically meaningful results should ask their provider about Progesterone, LC-MS/MS instead. For vaginal or transdermal progesterone users, standard immunoassay is appropriate.
Preparation
TIMING: For cycling women, progesterone must be drawn on day 19–22 of a 28-day cycle (approximately 7 days after ovulation) to capture peak luteal levels. Drawing at the wrong cycle day is the #1 cause of misleading results. Time of day matters — progesterone pulses, so morning draws may differ from afternoon. For women on progesterone BHRT (creams, capsules), draw at trough: 12–24 hours after your last dose. Oral progesterone (Prometrium) metabolizes differently than topical — expected levels differ by delivery method. Post-menopausal women on BHRT may have levels above standard ranges, which is expected. These notes reflect common practices in BHRT/functional medicine communities.
Reflects common practices in thyroid, BHRT, and functional medicine communities. This may differ from standard clinical guidelines. Not medical advice — always discuss with your provider.
General guidelines only. Requirements vary by lab and individual. Confirm with your provider before adjusting any medications.
Turnaround Time
Varies by lab
Clinical Notes
Timed with menstrual cycle (day 21 for ovulation confirmation)
ICD-10 Codes
Common diagnosis codes associated with this test. Codes are assigned by your provider.
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Lab Codes
Proprietary codes used by each lab for this test.
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For informational purposes only
This page is for educational and research purposes only and does not constitute medical advice, diagnosis, or treatment recommendations. ICD-10 and CPT codes are assigned by your healthcare provider. Always consult a qualified healthcare provider before ordering any lab test or making decisions about your health.