Finding the right tests…
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Finding the right tests…
Hormonal
Progesterone is made mainly by your ovaries after you ovulate, and this test measures how much is in your blood at the time of the draw. Because the level rises only after an egg is released, your doctor often uses it to confirm that ovulation has actually happened, which matters when you're being investigated for infertility. In early pregnancy, a progesterone level can help assess whether a pregnancy is developing normally or whether there's a higher risk of miscarriage or an ectopic pregnancy. The result only makes sense against the day of your cycle or week of pregnancy it was drawn on, so your doctor will ask when your last period started.
This test reports the amount of progesterone in your blood, in nanograms per millilitre. Because progesterone is only released in meaningful amounts after ovulation, a value drawn too early or too late in your cycle can look artificially low even in someone ovulating normally, so your doctor times the draw around day 21 of a typical cycle or adjusts it to your actual cycle length. In pregnancy, the reference range shifts substantially by trimester as the placenta takes over progesterone production from the ovary. A single blood sample from a vein in your arm is all that's needed.
Progesterone comes mainly from the corpus luteum, the structure left behind in the ovary after an egg is released, and its main job is preparing and maintaining the lining of the uterus for a pregnancy. Because it only rises once ovulation has actually happened, a progesterone level drawn about a week before your period is one of the more direct ways to confirm ovulation occurred that cycle.
A progesterone level that stays low through the second half of your cycle suggests ovulation didn't happen, which is a common line of investigation in irregular periods or difficulty conceiving. Doctors also use it to check whether fertility treatment is triggering ovulation as intended.
Once you're pregnant, the corpus luteum keeps making progesterone until around six weeks, when the placenta takes over. A progesterone level checked early in pregnancy can add information alongside hCG and ultrasound when there's concern about an ectopic pregnancy or a pregnancy that isn't developing normally, though it isn't used on its own to make either diagnosis.
Because the expected range shifts so much by cycle day and by trimester, a progesterone result only means something once your doctor knows exactly when it was drawn.
A level of 5 to 20 ng/mL around the middle of the luteal phase, roughly a week before your period, generally suggests ovulation happened, based on MedlinePlus reference values. Before ovulation, progesterone normally sits below 1 ng/mL. Ranges vary by lab, so check the figures on your own report.
Progesterone rises only after ovulation and falls again before your period, so a result depends heavily on exactly when in your cycle it's drawn. Testing too early can show a low result even when ovulation happened normally.
They rise steadily through pregnancy — roughly 11 to 90 ng/mL in the first trimester, 26 to 89 ng/mL in the second, and 48 ng/mL or higher, sometimes well over 150 ng/mL, in the third, per MedlinePlus reference ranges. These ranges are wide, so your doctor interprets a single value alongside other findings.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
A low level can be one signal your doctor weighs alongside hCG trends and ultrasound findings when assessing miscarriage or ectopic pregnancy risk, but it isn't used alone to make that diagnosis. Talk to your doctor about what your specific result means for your pregnancy.
No fasting or other special preparation is needed before this blood test.
Yes. Because PCOS often involves irregular or absent ovulation, progesterone levels in the second half of the cycle can stay low, which is one of the patterns doctors look for when investigating PCOS.