What is Progesterone?

Progesterone is a steroid hormone that plays a key role in the menstrual cycle and pregnancy. 

Progestin–a synthetic form of progesterone–can be taken as a form of birth control, to prevent premature labor, or as part of hormone replacement therapy during menopause. Progesterone also plays a role in gender-affirming care for trans women.

Learn more about progesterone, including what it does, typical progesterone levels, and how it can be taken as a medication.

What Does Progesterone Do?

Progesterone is a key reproductive hormone that plays an important role in regulating the menstrual cycle, preparing the body for implantation, and maintaining a healthy pregnancy.

The ovaries produce progesterone during the luteal phase–the second half of the menstrual cycle, which occurs after ovulation. During this time, progesterone levels rise and estrogen levels decrease as your body prepares for possible implantation. If fertilization doesn’t occur, the drop in progesterone signals to your body that it’s time for your period to start. 

During pregnancy, progesterone is released by the placenta (the organ that provides the fetus with key nutrients and oxygen). It helps to prevent early uterine contractions and prepare the breasts to produce milk. 

Finally, progesterone affects the body’s overall hormonal balance. Through its impact on the levels of other sex hormones (such as estrogen and testosterone), progesterone can help to protect against heart disease and bone loss over time. It also helps to promote sleep and provide a calming effect.

Progesterone Levels

Progesterone levels can be measured with a simple blood test. Your healthcare provider may want to test your progesterone levels to track ovulation or to determine possible reasons for repeated miscarriages, a recent ectopic pregnancy, or infertility. 

Normal progesterone levels vary widely based on your age, pregnancy status, and menstrual cycle. Typical serum (blood) progesterone ranges are:

• Male: less than 1 nanogram per milliliter (ng/mL)
• Female (follicular phase, or before ovulation): less than 1 ng/mL
• Female (luteal phase, or after ovulation): 5-20 ng/mL
• First trimester of pregnancy: 11.2-90.0 ng/mL
• Second trimester of pregnancy: 25.6-89.4 ng/mL
• Third trimester of pregnancy: 48-300 (or more) ng/mL
• After menopause: less than 1 ng/mL
  

Low Progesterone

Low progesterone can be caused by a variety of conditions, such as:

• High levels of cortisol (the stress hormone)
• High levels of prolactin (the hormone that stimulates milk production)
• Ectopic pregnancy
• Thyroid conditions
• Polycystic ovarian syndrome (PCOS)
• Menopause

Signs and symptoms of low progesterone levels may include:

• Irregular periods, including skipped cycles and abnormal spotting
• Bleeding during pregnancy
• Repeated miscarriages
• Premature labor
• Reduced libido

High Progesterone

High progesterone levels may be caused by:

• Pregnancy
• Ovulation
• Pregnancy with multiple babies
• Molar pregnancy
• Ovarian cysts
• Adrenal cancer
• Ovarian cancer

Symptoms of higher-than-normal progesterone are often similar to the signs of premenstrual syndrome (PMS), such as:

• Depression
• Anxiety
• Irritability
• Bloating
• Fatigue
• Breast tenderness

Taking Progesterone

Synthetic progesterone can be taken orally (as a tablet), vaginally (as a suppository or topical cream), or via injection. It’s used to treat a variety of conditions, including unwanted symptoms of menopause and problems with the menstrual cycle.

Here are the medical uses for progesterone and why your healthcare provider may prescribe it you.

Hormone Replacement Therapy

Progestin is often prescribed as part of hormone replacement therapy (HRT) for people going through perimenopause or menopause–defined as the stage of life, often during one’s 40s or 50s, when periods permanently come to a halt. 

HRT typically involves taking estrogen and, if you still have a uterus, progesterone. It can be administered via oral tablets, vaginal creams or rings, or skin patches. This can help to relieve symptoms such as vaginal dryness, hot flashes, reduced sex drive, mood swings, and night sweats. It can also work to prevent bone density loss, reducing your risk of fractures and other injuries.

Progesterone is also sometimes prescribed to trans women as part of gender-affirming care. When taken alongside estrogen, progesterone can help to protect against osteoporosis and heart disease. It can also increase breast development and lower testosterone production.

Birth Control

Progestin is used in several different types of hormonal birth control to prevent pregnancy. Types of birth control that contain progestin include “the pill”–sometimes on its own in progestin-only pills and sometimes alongside estrogen in the “combination pill”–as well as the hormonal intrauterine device (IUD) and the birth control implant. 

Progestin works to prevent pregnancy by thickening cervical mucus, which makes it more difficult for sperm to fertilize the egg. It can also thin out the uterine lining and prevent ovulation.

Treating Amenorrhea

Some people with amenorrhea (no periods) are prescribed a progestin medication–such as Provera (oral medroxyprogesterone acetate) via tablets or progesterone in oil via injection–to restart their menstrual cycle. 

After taking Provera for five to 10 days or receiving one progesterone injection, most people get their period within two weeks. This is known as the “progesterone challenge test” or “progesterone withdrawal test."

Preventing Preterm Birth

Because progesterone works to inhibit uterine contractions, it’s sometimes given to prevent premature labor. 

People who have had previous preterm births may receive progesterone shots to stave off early contractions. Meanwhile, vaginal gels or suppositories containing progesterone might be administered if you’ve been diagnosed with a short cervix at 24 weeks or earlier during a previous pregnancy.

Safety

Progesterone is typically safe and doesn’t usually cause severe side effects. Many people take progesterone while pregnant or breastfeeding. 

Tell your healthcare provider before taking progesterone if:

• you have ever had an allergic reaction to progesterone or any form of hormonal birth control
• you take any other prescription medications
• you take St. John’s wort
• you’ve ever had breast cancer, uterine cancer, ovarian cancer, depression, seizures, migraine, asthma, blood clots, stroke, gallbladder disease, kidney disease, heart disease, or liver disease
• you are pregnant or want to become pregnant

Side Effects

Common side effects of progesterone include:

• Breast tenderness
• Nausea and vomiting
• Fatigue
• Diarrhea
• Joint or muscle pain
• Headache
• Mood swings
• Depression
• Irritability
• Unusual vaginal discharge

Serious side effects from taking progesterone are rare. Seek medical help right away if you experience any of the following:

• Signs of anaphylaxis (a severe allergic reaction), such as difficulty breathing, swelling in the face or lips, or hives
• Chest pain
• Severe lightheadedness
• Limb weakness
• Swelling in one or both legs
• Vision problems
• Vaginal bleeding
• Abdominal swelling or pain
• Difficulty speaking
• Lumps in the breasts
• Racing heart
• Seizures

Other Ways to Increase Progesterone

Research suggests that there are several ways to increase your progesterone levels naturally, including:

• Reducing stress: Cortisol, often known as “the stress hormone,” is linked to reduced progesterone levels. Managing your stress with mindfulness techniques, deep breathing exercises, and mental health treatment if necessary may help to boost your progesterone.
• Managing weight: Obesity can increase estrogen levels and lower progesterone. Exercising regularly, staying hydrated, and eating nutrient-rich foods may help. 
• Eating an anti-inflammatory diet: Inflammation has been linked to “estrogen dominance,” which happens when your estrogen and progesterone levels are out of balance. A diet rich in omega-3 fatty acids, fiber, and cruciferous vegetables can help to balance your hormones.
  

A Quick Review

Progesterone is a hormone that plays an important role in regulating the menstrual cycle after ovulation, getting the body ready for implantation, preparing the breasts for milk production, and preventing premature labor during pregnancy. It’s produced by the ovaries during the second half of the menstrual cycle and by the placenta during pregnancy.

Synthetic forms of progesterone, known as progestins, can be taken as hormonal birth control. They can also be used to treat menstrual irregularities, relieve symptoms of menopause, and prevent premature labor during pregnancy. Trans women are sometimes prescribed progesterone as part of gender-affirming medical care.