Hormones are chemical messengers in your body that affect a range of bodily functions, from sleep-wake cycles to digestion.

Progesterone is one of two female sex hormones, the other being estrogen. Its main functions are regulating menstruation and supporting pregnancy in the female body.

Read on to learn more about progesterone’s function and typical levels.

Progesterone is produced in the corpus luteum of the ovaries. This is a temporary gland that’s produced following the release of an egg from the ovary.

The adrenal glands and the placenta can also produce progesterone.

During the menstrual cycle

In the middle of a person’s menstrual cycle, a rise in levels of luteinizing hormone leads to ovulation. Ovulation refers to the release of an egg from one of the two ovaries. Once the egg is released, the corpus luteum forms and begins producing progesterone.

Progesterone helps to prepare the body for pregnancy. For example, it causes lining of the uterus, called the endometrium, to thicken. This provides a good environment for implantation by a fertilized egg.

If the egg isn’t fertilized, the corpus luteum breaks down, leading to a drop in progesterone levels. This decrease causes the thickened endometrium to break down, causing the beginning of a menstrual period.

During pregnancy

If an egg is fertilized, the corpus luteum doesn’t break down and continues to produce progesterone. This progesterone stimulates blood vessels to supply the endometrium. It also prompts the endometrium to provide nutrients to the developing embryo.

Once the placenta has formed, it also produces progesterone. Eventually, the placenta becomes to primary producer of progesterone.

Levels of progesterone remain elevated throughout pregnancy. These elevated levels also prevent the body from producing additional eggs during the pregnancy.

Eventually, progesterone also helps to trigger lactation.

In males

Progesterone is also produced in the adrenal glands of males. Its function is associated with sperm development.

There are a number of reasons that a healthcare provider may want to test progesterone levels.

Some of them include:

Progesterone levels are measured through a blood test. It’s important to remember that progesterone levels fluctuate throughout the menstrual cycle, so levels can vary throughout the month.

Progesterone levels are measured in nanograms per milliliter (ng/mL). The chart below lists normal levels of progesterone for an adult female during different points of the menstrual cycle and pregnancy.

StageProgesterone level (ng/mL)
pre-ovulation< 0.89
ovulation≤ 12
post-ovulation1.8–24
first trimester11–44
second trimester25–83
third trimester58–214

Progesterone is found in much lower levels in men and isn’t typically tested unless adrenal gland dysfunction is suspected. Normal levels are less than 0.20 ng/mL.

Keep in mind that results can very between laboratories. If you’re unsure about your test results, contact your healthcare provider.

High levels of progesterone typically don’t cause any negative health effects. Having high levels of progesterone won’t cause any negative effects on your health. Progesterone levels naturally reach high levels during pregnancy.

In fact, progesterone is present in oral contraceptives because it can trick the body into not ovulating.

However, high progesterone in someone who isn’t pregnant could be a sign of an underlying health condition, including:

Low progesterone levels can affect both menstruation and fertility. Progesterone helps to promote a good environment for a fertilized egg. When progesterone levels are low, it’s harder for fertilized egg to develop and grow.

Low levels of progesterone can also contribute to certain conditions, including:

Progesterone is a hormone that’s vital for menstruation, pregnancy, and sperm production. It’s be produced in a variety of locations, including the corpus luteum, placenta, and adrenal glands.

Progesterone levels fluctuate throughout the cycle and reach high levels during pregnancy. However, if levels get too low, it can lead to health issues, including infertility.