Serum Progesterone Levels

Progesterone is a hormone produced mainly in the ovaries by the corpus luteum (what the follicle turns into after it releases the egg). Progesterone helps prepare the uterus for the implantation of a fertilized egg. If a fertilized egg implants, progesterone then helps the uterine lining (endometrium) to maintain the pregnancy.

Why Would You Have Progesterone Levels Checked?

You might have your progesterone checked if you have having trouble getting pregnant. If your progesterone levels are elevated within a normal range, it confirms that you are ovulating. This is a very common test for women who are having trouble becoming pregnant.

If you have had a miscarriage, stillbirth, or unusual bleeding from your uterus, your progesterone may also be checked.

When Are Progesterone Levels Checked?

Your progesterone level is usually checked six to eight days after you ovulate (about day 21 of a day 28 cycle). This is because progesterone levels rise following ovulation, peaking five to nine days after ovulation. This is known as your luteal phase. After the midluteal period, your serum progesterone levels will begin to fall if the egg is not fertilized.

If your menstrual cycle is irregular, you may be asked to come in for a number of blood tests until your period begins. This can pinpoint when (or if) ovulation occurs and help make sure you get an accurate test result.

The Progesterone Test

The progesterone test is looking for the amount of progesterone in your blood on the day of the test.

If your progesterone level is elevated within a certain range during the luteal phase, it means you are ovulating. If your progesterone level is not elevated, it can mean that you are not ovulating. Obesity, insulin resistance, high levels of stress, poor diet and lack of exercise can all contribute to low progesterone levels

Higher levels of progesterone than normal can be caused by adrenal cancer, ovarian cancer or a condition known as congenital adrenal hyperplasia.

Consistently elevated (beyond just the luteal phase of your cycle) progesterone levels are found in pregnancy. If you are already pregnant, low levels of progesterone are associated with fetal death, threatened abortion and toxemia of pregnancy.

Progesterone Levels and Fertility Treatment

If your midluteal serum progesterone level is low, the first step is to have it repeated in another cycle to confirm the result. If it is the same or still low, you may need ovarian stimulation to help you ovulate. Progesterone supplements are sometimes prescribed. High progesterone would most likely be addressed by treating the underlying cause of the problem.

Women with low progesterone and a history of miscarriages may be given progesterone supplements as soon as pregnancy is confirmed. This can help reduce the chances of another miscarriage by improving the intrauterine environment.