Progesterone is an important hormone produced by the body. Serum progesterone tests may be used to identify issues with fertility and other health problems.

Progesterone is a hormone that your body produces. Although everyone produces progesterone, it’s mainly produced in the ovaries, meaning that those who are assigned female at birth tend to have higher levels.

Progesterone helps prepare the uterus for a fertilized egg. If you become pregnant, progesterone helps you remain pregnant.

Progesterone also inhibits your milk production during pregnancy. When you go into labor, your progesterone levels drop, which helps trigger your milk production.

Additionally, progesterone is involved in the creation of sperm, or spermatogenesis, in the male reproductive organs.

If you’re having trouble getting pregnant, a doctor may order a progesterone test to measure the amount of progesterone in your blood.

The results can give them an indication of whether or not you’re ovulating, which can help them diagnose and manage potential fertility problems.

A doctor might also order this test if you’re pregnant and they suspect you’re at risk of ectopic pregnancy or miscarriage, both of which can be associated with low or abnormal progesterone levels.

An ectopic pregnancy is an embryo that implants outside of the uterus, usually in the fallopian tube, cervix, or abdominal cavity. A miscarriage is a failed pregnancy or pregnancy loss.

To conduct a serum progesterone test, a doctor will collect a sample of your blood to send to a laboratory.

They may ask you take certain steps to prepare for the test.

For example, you should tell the doctor about any medications you’re taking. Some drugs, such as birth control pills and progesterone supplements, can affect the results of your test.

Other drugs, such as blood thinners, can also raise your risk of complications from a blood draw.

A doctor may ask you to stop taking certain medications before you get your blood drawn.

A doctor may collect a sample of your blood in their office or send you to another site to have your blood drawn. The person drawing your blood will start by cleaning an area of your skin directly over a vein.

Next, they will insert a needle into your vein. They will draw blood through the needle into a vial or tube. Then they will send your blood sample to a laboratory for testing.

Any time you have your blood drawn, you face some risks. For most people, these risk are minor.

You will probably feel some pain when the needle is inserted into your vein and you might bleed for a few minutes after the needle is removed. A bruise might also develop in the area surrounding the puncture site.

More serious complications are rare. These include fainting, inflammation of your vein, and infection at your puncture site.

If you have a bleeding disorder, the risks of a blood draw are higher.

Your serum progesterone level will be measured in nanograms per deciliter (ng/dL).

Once your results are ready, the laboratory will send them to a doctor. Normal results can vary, depending on your sex, age, menstrual cycle, and whether or not you’re pregnant.

If you’re a person who menstruates, your blood progesterone level should be low at the beginning of each menstrual cycle and peak several days after you ovulate. Then it should fall back to low levels, unless you’ve become pregnant.

Normal test results

For people assigned female at birth, normal serum progesterone test results fall in the following ranges:

  • At the beginning of the menstrual cycle: 0.89 ng/mL or under
  • In the middle of the menstrual cycle: 1.8–24 ng/mL
  • During the first trimester of pregnancy: 11–44 ng/mL
  • During the second trimester of pregnancy: 25–83 ng/mL
  • During the third trimester of pregnancy: 58–214 ng/mL
  • After menopause: 0.2 ng/mL or under

Reference ranges for progesterone may vary for different labs and depending on your individual risk factors and cycle.

Abnormal test results

Your test results are considered abnormal if they fall outside the normal ranges. In some cases, a single abnormal test result reflects normal fluctuations in your progesterone levels.

Your progesterone levels can fluctuate a lot, even over the course of a single day. In other cases, abnormally high or low progesterone levels may be a sign of an underlying health problem.

In addition to pregnancy, high progesterone levels might be associated with:

Low progesterone levels may be associated with:

Ask a doctor what your test results mean. They can help you understand the potential causes of abnormally high or low progesterone levels.

They can also discuss appropriate follow-up steps.

Depending on your test results, a doctor may also recommend additional tests or treatments.