What is a progesterone test?

A progesterone test measures the level of progesterone in a sample of your blood. Progesterone is a hormone that's made mainly by the ovaries, which are two glands in the female reproductive system that contain eggs.

Each month, progesterone prepares your uterus for pregnancy. During the first half of a normal menstrual cycle, estrogen makes the lining of your uterus grow thicker. In the second half, an ovary releases an egg and your progesterone levels begin to rise. Progesterone gets the lining of your uterus ready for a fertilized egg to attach (implant) and grow into a fetus.

If you don't become pregnant, your progesterone levels will fall. The lining of your uterus will thin, and your uterus will get rid of the extra blood and tissue when your menstrual period begins.

If you become pregnant, progesterone levels will continue to rise to support the pregnancy. High levels of progesterone:

• Cause cells in the lining of your uterus to produce proteins that are necessary for the attachment of a fertilized egg.
• Cause the creation of white blood cells that will make sure your immune system doesn't attack the fertilized egg.
• Prevent the uterus from contracting (squeezing) and causing pre-term labor.
• Play a role in the development of the placenta, an organ that grows in the uterus to provide nutrients and oxygen to the fetus.

Once the placenta is fully formed, it will make much of the progesterone you need for a healthy pregnancy.

Other names: serum progesterone, progesterone blood test, PGSN

What is it used for?

A progesterone test can help show whether low progesterone levels are causing female infertility (problems getting pregnant after a year of trying) or problems during pregnancy.

A progesterone test may also be used to help:

• Check to see if fertility treatments are working.
• Find out your risk of a miscarriage (loss of a pregnancy before 20 weeks).
• Diagnose an ectopic pregnancy, which is a fertilized egg that tries to grow outside of the uterus. The egg cannot grow into a fetus when it's in the wrong place. It must be removed to avoid damage to your organs. This can be a medical emergency.
• Check the health of you and your fetus during a high-risk pregnancy.
• Diagnose ovarian cancer or problems with your adrenal glands. Normally, your adrenal glands make small amounts of progesterone. High levels of progesterone may be a sign of an adrenal gland disorder in both females and males.
• Diagnose the cause of abnormal uterine bleeding.

Why do I need a progesterone test?

You may need a progesterone test if:

• You are having trouble getting pregnant. A progesterone test can help your health care provider see if your ovaries are releasing eggs (ovulating) normally.
• You are having fertility treatments.
• You are having abnormal bleeding when you're not pregnant.
• You have signs of low progesterone such as irregular menstrual periods, hot flashes, and trouble sleeping.
• You have signs of high progesterone such as vaginal dryness and bloating.

It's common to have your progesterone levels tested as part of a panel of tests you may get if you're pregnant. You may also need a progesterone test while pregnant if:

• You're having progesterone therapy to prevent a miscarriage.
• Your provider wants to check the health of your pregnancy because you have a higher risk for miscarriage or other pregnancy complications.
• You have signs of a miscarriage or ectopic pregnancy, such as cramps or bleeding.

What happens during a progesterone test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

You usually don't need any other preparations for a progesterone test. In certain cases, you may need to know the first day of your last menstrual period. Your provider will tell you if you need to stop taking any medicines before the test. But never stop taking medicine unless your provider tells you.

Are there any risks to the test?

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

The meaning of your test results depends on:

• Why you were tested.
• Where you were in your menstrual cycle when your blood sample was taken.
• Whether or not you're pregnant.

High progesterone levels:

• When you're not pregnant may be linked to:
  • A cyst on your ovaries.
  • Ovarian cancer.
  • Adrenal gland problems, including adrenal gland cancer, or an inherited disorder called congenital adrenal hyperplasia (CAH).
• Higher than expected progesterone levels when you are pregnant, may mean you're having two or more babies.

High progesterone levels may also be a sign of a molar pregnancy, which is an abnormal growth of tissue in the uterus. It's caused by a fertilized egg with such severe genetic problems that it cannot become a fetus. The growth can turn into cancer and must be removed.

Low progesterone levels:

• When you're not pregnant, may be linked to:
  • Not ovulating normally.
  • Not having a menstrual period (amenorrhea).
  • Polycystic ovary syndrome (PCOS), a condition that causes missed periods and unpredictable ovulation.
  • High stress. Too much of the stress hormone cortisol can affect your body's ability to make progesterone.
  • Perimenopause. This is the time just before menopause.
  • Low cholesterol.
• When you're pregnant, may be linked to:
  • Ectopic pregnancy.
  • Miscarriage or a high risk of miscarriage.
  • Pre-eclampsia.

Your provider can explain what your test results say about your health.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about a progesterone test?

Because progesterone levels change throughout your pregnancy and menstrual cycle, you may need to be tested several times.