Progesterone Test

About this test

This test measures the level of progesterone in your blood — a hormone produced mainly by the ovaries after ovulation, and by the placenta during pregnancy. Progesterone plays a key role in regulating the menstrual cycle, preparing the uterine lining for a fertilized egg, and maintaining early pregnancy.

Timing is critical for this test. Progesterone is very low during the first half of the menstrual cycle and rises sharply after ovulation (during the luteal phase, typically days 18–24 of a 28-day cycle). The test is most informative when drawn at the right point in your cycle, which your clinician will advise on based on your situation.

Components

• Progesterone (serum): Measures the amount of progesterone circulating in your blood. Results are interpreted differently depending on cycle timing, age, and whether you are pregnant. Low mid-luteal progesterone may suggest anovulation (failure to ovulate) or insufficient ovarian function. In early pregnancy, serial progesterone measurements can help assess whether the pregnancy is progressing normally.

Who is this test for?

This test is most commonly used by women who are tracking ovulation, trying to conceive, or investigating irregular menstrual cycles. It is also ordered in early pregnancy to assess whether progesterone levels are adequate to support the pregnancy, and by women experiencing recurrent miscarriage. Testing is typically timed to the middle of the second half of the menstrual cycle.