Progesterone is a hormone that plays an important role in your reproductive system. Hormones are chemical messengers that tell your body how to work. In women or people assigned female at birth (AFAB), progesterone supports menstruation and helps maintain the early stages of a pregnancy.
The main function of progesterone is to prepare the endometrium (lining of your uterus) for a fertilized egg to implant and grow. If a pregnancy doesn’t occur, the endometrium sheds during your menstrual period. If conception occurs, progesterone increases to support the pregnancy.
Ovulation (when your ovary releases an egg) occurs around the middle of a person’s menstrual cycle. The corpus luteum forms from the empty egg follicle and begins producing progesterone. Your corpus luteum is a temporary gland that helps support the beginning of a pregnancy if conception occurs during that cycle. Progesterone works by thickening your uterine lining and creating a good environment for a fertilized egg to implant.
If an egg isn’t fertilized during that cycle (meaning you don’t get pregnant), the corpus luteum breaks down, which decreases progesterone levels. Decreasing progesterone levels means your uterine lining thins and breaks down, causing the beginning of your menstrual period.
If an egg is fertilized by sperm and conception occurs, the corpus luteum doesn’t break down and continues to make more progesterone. Your uterine lining is thick and rich in blood vessels, which provides nutrients for the fertilized egg (now an embryo). Once the placenta forms, it’ll take over progesterone production.
During pregnancy, progesterone levels increase each trimester, reaching their highest level in your third trimester (weeks 28 to 40 of pregnancy). Progesterone levels decline in the years leading up to menopause, when ovulation stops.
Progesterone is critical in supporting a pregnancy because it thickens your uterine lining. A thick uterine lining helps a fertilized egg grow into an embryo, and then to a fetus.
Progesterone levels continue to rise during pregnancy. High progesterone levels prevent your body from ovulating while you’re pregnant. It also suppresses uterine contractions, which helps you avoid preterm labor. Finally, progesterone helps your breasts prepare for breastfeeding (chestfeeding).
Because progesterone is so important in maintaining the early stages of pregnancy, low progesterone levels may make it hard for you to conceive and may put you at higher risk for miscarriage.
Progesterone does several things, including:
A gland called the corpus luteum produces progesterone. Your corpus luteum is a temporary gland that develops after you ovulate (release an egg from your ovary). It’s responsible for maintaining progesterone levels after conception and fertilization to support a pregnancy.
Your adrenal glands and placenta also make progesterone.
Low progesterone can affect your body in several ways, sometime causing noticeable symptoms. High progesterone levels don’t typically have a negative impact on your health. In rare cases, it can be a sign of ovarian or adrenal cancer.
Symptoms of low progesterone in people who aren’t pregnant include:
Since progesterone maintains your uterine lining during pregnancy so a fetus can grow, low levels can make it hard for you to stay pregnant. You need progesterone levels to stay high until you’re ready to give birth.
If you have low progesterone, you’re at risk for pregnancy complications such as:
A blood test (a PGSN or progesterone test) can be used to test progesterone levels. It’s most commonly used to determine ovulation.
Progesterone levels fluctuate throughout your menstrual cycle. Levels rise after ovulation and continue to rise if pregnancy occurs. Your healthcare provider is the best person to determine what your progesterone level should be depending on where you are in your menstrual cycle or if you’re pregnant.
Some women or people AFAB need to take progesterone supplements. Your healthcare provider may prescribe progesterone if you:
As you begin to transition into menopause, your ovaries no longer produce high levels of estrogen and progesterone. Changes in these hormone levels can cause uncomfortable symptoms. Common symptoms include:
Your provider may recommend estrogen progesterone hormone therapy (EPT) to relieve these symptoms. Also called combination therapy, this form of hormone therapy combines estrogen and progesterone.
Weight gain isn’t a direct side effect of progesterone. While hormones in general can affect your hunger levels and weight, having too much or too little progesterone alone isn’t usually a cause of weight gain.
Yes, progesterone levels may make you feel more tired.
Progestin is an artificial (synthetic) form of progesterone. Scientists created progestin in a lab. Healthcare providers use it if your body isn’t producing enough progesterone on its own. Progestin is available as pills, vaginal gels, injections and intrauterine devices (IUD). Your provider may give you progestin for:
Progesterone and estrogen are like hormonal teammates in your body. They work together to regulate certain body processes like menstruation. If you have low progesterone, estrogen dominates and your body processes aren’t regulated. When this happens, you could experience:
Progesterone and estrogen also work together in combination hormone replacement therapy (HRT), which treats symptoms of menopause. They work together in certain oral contraceptives (birth control pills) to prevent pregnancy, as well.
Only a healthcare provider can determine your progesterone levels. Contact your provider if you have spotting or cramping during pregnancy, or if you have irregular periods.
Although research is limited, eating foods that contain certain vitamins may help support healthy progesterone levels. These include:
A note from Cleveland Clinic
Progesterone plays an important role in your menstrual cycle and pregnancy. Progesterone creates a healthy uterine lining to support a fertilized egg, embryo and fetus. If progesterone levels are too low during pregnancy, it could cause complications such as bleeding or miscarriage. Providers may prescribe progesterone supplements to regulate your menstrual cycle, reduce symptoms of menopause or as birth control. Talk to your healthcare provider if you have any questions about progesterone or its role in your body.
Last reviewed by a Cleveland Clinic medical professional on 12/29/2022.