A progesterone test measures the amount of the hormone progesterone in a blood sample. Progesterone is a female hormone produced by the ovaries during release of a mature egg from an ovary (ovulation). Progesterone helps prepare the lining of the uterus (endometrium) to receive the egg if it becomes fertilized by a sperm. If the egg is not fertilized, progesterone levels drop and menstrual bleeding begins.

During pregnancy, the placenta also produces high levels of progesterone, starting near the end of the first trimester and continuing until the baby is born. Levels of progesterone in a pregnant woman are about 10 times higher than they are in a woman who is not pregnant.

Some types of cancer cause abnormal progesterone levels in men and women.

Why It Is Done

A progesterone test is done to:

• Help find the cause of infertility.
• Monitor the success of medicines for infertility or the effect of treatment with progesterone.
• Help determine whether ovulation is occurring.
• Assess the risk of miscarriage.
• Monitor the function of the ovaries and placenta during pregnancy.
• Help diagnose problems with the adrenal glands and some types of cancer.

How To Prepare

You may be asked to stop taking medicines (including birth control pills) that contain estrogen or progesterone, or both, for up to 4 weeks before having a progesterone test.

Tell your health professional if you have had a test that used a radioactive substance (tracer) within the last 7 days. Recent tests such as a thyroid scan or bone scan that used a radioactive tracer can interfere with the test results.

Let your health professional know the first day of your last menstrual period. If your bleeding pattern is light or begins with spotting, the first day is the day of heaviest bleeding.

Talk to your health professional about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will indicate. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

How It Is Done

The health professional drawing blood will:

• Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
• Clean the needle site with alcohol.
• Put the needle into the vein. More than one needle stick may be needed. Attach a tube to the needle to fill it with blood.
• Remove the band from your arm when enough blood is collected.
• Apply a gauze pad or cotton ball over the needle site as the needle is removed.
• Apply pressure to the site and then a bandage.

For a woman who is having problems with her menstrual cycle or who cannot become pregnant, more than one blood sample for progesterone testing may be needed to help identify the problem. A sample may be taken each day for several days in a row.