Normal progesterone levels vary depending on a person's sex and whether a pregnancy is present. Each individual is also slightly different and generally a range is used to see if a patient has normal levels. If a progesterone measurement falls outside the normal range, it can be an indicator of a medical problem such as a hormone imbalance or failing pregnancy. Determining levels of progesterone in the body is done with a simple blood test.
While progesterone is often considered a female hormone because it plays such an important role in conception, maintaining a pregnancy, and preparing the body for labor and delivery, it is also present in men. Normal progesterone levels in men are less than one nanogram per milliliter. The hormone plays a role in developing other sex hormones and thus is expected to be present in trace amounts.
In women after puberty and before menopause, progesterone levels fluctuate over the course of the menstrual cycle. Before ovulation, levels fall to levels comparable to those seen in men. In the middle of the cycle, they rise to between five and 20 nanograms per milliliter. They will drop if implantation does not occur. Postmenopausal women have very low normal progesterone levels because their bodies are not preparing to support a pregnancy, and usually have levels around those seen in men as well.
During pregnancy, normal progesterone levels steadily rise. In the first trimester, they will range from around 11 nanograms per milliliter to 90 nanograms per milliliter. Over the course of the second trimester of pregnancy, they can be between 25 nanograms per milliliter and almost 90 nanograms per milliliter. In the third trimester, levels drop back down to between 42 and 48 nanograms per milliliter. Once the baby is born, normal progesterone levels will start to level off. Some women experience issues like depression and stress when their hormones return to normal levels after a pregnancy.
Abnormal progesterone levels during pregnancy can indicate that something is going wrong, or can be the cause of a problem with a pregnancy. Without enough progesterone, the fetus may not be able to develop properly. In addition, other physical changes that happen with pregnancy, such as the development of milk, will not occur. If a pregnant woman has abnormal levels, additional testing is recommended to find out why and provide treatment. Women in treatment for infertility are also monitored for signs of problems with their progesterone.