Progesterone

Progesterone is a steroid hormone produced mainly by the ovaries after ovulation and by the placenta during pregnancy. Smaller amounts are made by the adrenal glands in all people. It prepares the uterine lining for implantation and supports early pregnancy, and it also helps regulate the menstrual cycle.

This test measures the amount of progesterone in your blood. Your clinician may time the test to a specific point in your cycle, or order repeat measurements, because progesterone naturally changes across the month. It can also be measured when you are using fertility treatments or hormone therapy.

Clinicians use progesterone testing to help confirm whether ovulation has occurred, to evaluate irregular periods, and to investigate difficulties getting pregnant. In early pregnancy, progesterone helps maintain the uterine lining, so testing may be used alongside other tests when there is concern about pregnancy health.

Progesterone levels can also provide clues about ovarian or adrenal disorders and guide monitoring during fertility treatments or when you are using progesterone medications. Your results are interpreted together with your symptoms, cycle timing, pregnancy status, ultrasound findings, and other hormone tests.

Your result is interpreted in the context of your menstrual cycle or pregnancy. In people who ovulate, progesterone is typically lower before ovulation and higher afterward, so a single measurement may not tell the full story. If timing is uncertain, your clinician may repeat the test or use ovulation tracking to better align testing with your cycle.

If your level is lower than expected for the timing, it may suggest that ovulation did not occur or that the ovary is not producing much progesterone. Higher values can occur after ovulation, in pregnancy, with certain ovarian or adrenal conditions, or with progesterone medication. Discuss any hormones, supplements, or fertility drugs you use, because they can affect results. Do not start or stop medications without medical advice. Your clinician will recommend next steps, which may include repeat testing, ultrasound, or additional hormone tests.