A progesterone test is a blood test that measures a hormone called progesterone.

Progesterone is important in pregnancy. It prepares your body to support a fertilized egg. If you’re pregnant, progesterone also triggers your breasts to make milk.

Progesterone helps control your period, too. Generally, progesterone levels go up each month when you ovulate and your body is ready to get pregnant. If you don’t get pregnant, progesterone goes back down and triggers your period. If you get pregnant, progesterone will keep going up. In pregnancy, progesterone is about 10 times its normal level.

By itself, a progesterone test isn’t enough to diagnose any particular problem. But it could help, along with other tests. You might also use a home urine test for progesterone to see when you ovulate and are most likely to get pregnant.

Progesterone Test Uses

Your doctor may use a progesterone test to:

• Find out why you aren’t getting pregnant when you’re trying
• Check if and when you are ovulating
• Check whether you’re at high risk of miscarriage during pregnancy
• Monitor a high-risk pregnancy
• Diagnose an ectopic pregnancy, when a fertilized egg implants outside your womb

Progesterone Test Procedure

The test tells you what your level of progesterone is at that time. You don’t need to do anything to prepare. But it will help if you take note of when your last menstrual period started.

The test itself is simple. Your doctor, physician’s assistant, or another health care professional will insert a needle in a vein in one of your arms and take a bit of blood for testing in a lab.

Progesterone Test Results

Your results may be one of these:

Progesterone levels don’t fluctuate regularly. This would be determined through multiple tests. If the tests show that your progesterone levels don’t rise and fall on a monthly basis the way they should, you may not be ovulating or having regular periods. This could make it harder to get pregnant.

Low levels of progesterone. This could depend on what point in your cycle the test was done. If the test shows a lower than normal level of progesterone, it could be because:

• Your ovaries aren’t working the way they should, or you didn’t ovulate
• Possible unusual pregnancy

High levels of progesterone. If your test shows higher-than-normal levels of progesterone, it could be due to:

• Pregnancy with one or more babies
• Cysts on your ovaries
• A growth that causes symptoms of pregnancy (molar pregnancy)
• A disorder affecting your adrenal glands
• Ovarian cancer

Progesterone within normal levels. Progesterone levels in a certain range can signal that you have ovulated. The test should be done either 18 to 24 days after the first day of your period or 7 days before your next expected period.

Progesterone-Related Tests

If your doctor orders a progesterone test, you might also get:

• Other blood tests to check on your ability to get pregnant
• Home urine tests that look at progesterone byproducts as an indicator of ovulation
• An ultrasound to measure the thickness of the lining of your uterus
• A specific blood test, if you’re pregnant, to find out whether there are problems with the pregnancy