Progesterone: Function, Levels, Symptoms and Care
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer: What does progesterone do?
Progesterone prepares and maintains the uterine lining for implantation and pregnancy. It also helps regulate menstrual bleeding, prevents ovulation during pregnancy, suppresses uterine contractions, prepares the breasts for breastfeeding and supports mood, thyroid function and lactation. After ovulation, the corpus luteum begins producing progesterone. [1]
Core idea | Plain-language meaning |
Hormone | A chemical messenger involved in reproductive-system function. |
Main role | Prepares the uterine lining for a fertilized egg to implant and grow. |
After ovulation | The corpus luteum begins producing progesterone. |
During pregnancy | Levels rise; the placenta eventually takes over production. |
Testing | A blood progesterone test can be used, most commonly to determine ovulation. |
Interpretation | Results depend on cycle timing and whether pregnancy is present. |
What the research says
Progesterone did not significantly raise live births overall when bleeding occurred in early pregnancy. A multicenter, randomized, double-blind, placebo-controlled trial of 4,153 women with vaginal bleeding in early pregnancy compared twice-daily vaginal progesterone (400 mg) with placebo. Live birth after at least 34 weeks occurred in 75% of the progesterone group (1,513 of 2,025) and 72% of the placebo group (1,459 of 2,013), a relative rate of 1.03 (95% CI 1.00–1.07; P = 0.08), and adverse events did not differ significantly (Coomarasamy et al., N Engl J Med, 2019). [2]
Vaginal progesterone lowered preterm birth risk when the cervix was short. A meta-analysis of individual patient data from 974 women in 5 high-quality trials (498 given vaginal progesterone, 476 given placebo) with a midtrimester cervical length of 25 mm or less found a relative risk of preterm birth before 33 weeks of 0.62 (95% CI 0.47–0.81). Maternal adverse events, congenital anomalies and neurodevelopmental outcomes at 2 years did not differ between groups (Romero et al., Am J Obstet Gynecol, 2018). [3]
What is progesterone?
Progesterone is a hormone that plays an important role in the reproductive system. Hormones are chemical messengers that tell the body how to work. In females, progesterone supports menstruation and helps maintain the early stages of pregnancy. [1]
Its central role is preparing the endometrium, or uterine lining, for a fertilized egg to implant and grow. [1]
What is the main purpose of progesterone?
Progesterone thickens the uterine lining and creates an environment where a fertilized egg can implant. If conception does not occur, progesterone levels decrease and the lining thins and breaks down during menstruation. If conception occurs, progesterone increases to support the pregnancy. [1]
Progesterone and the menstrual cycle
Ovulation occurs around the middle of a person's menstrual cycle. After the ovary releases an egg, the empty egg follicle forms the corpus luteum, a temporary gland that begins producing progesterone. [1]
The corpus luteum helps support the beginning of a pregnancy if conception occurs during that cycle. Progesterone thickens the uterine lining and creates an environment for implantation. [1]
If the egg is not fertilized, the corpus luteum breaks down. Progesterone then decreases, the uterine lining thins and breaks down, and a menstrual period begins. [1]
Progesterone during pregnancy
If an egg is fertilized by sperm and conception occurs, the corpus luteum continues making progesterone. The uterine lining remains thick and rich in blood vessels, providing nutrients for the fertilized egg, which is now an embryo. [1]
Once the placenta forms, it takes over progesterone production. Progesterone levels increase during each trimester and reach their highest level in the third trimester, from weeks 28 to 40. [1]
What does progesterone do during pregnancy?
Progesterone is important for supporting a pregnancy because it thickens the uterine lining. This lining helps a fertilized egg grow into an embryo and then a fetus. [1]
Progesterone levels rise during pregnancy. Higher levels prevent ovulation while a person is pregnant, suppress uterine contractions (which helps avoid preterm labor) and help the breasts prepare for breastfeeding. [1]
Low progesterone during pregnancy may make it harder to conceive and may increase the risk of miscarriage. It is also associated with ectopic pregnancy and preterm labor. These associations do not determine the cause of any individual pregnancy symptom or outcome, and pregnancy concerns require individualized evaluation.
What else does progesterone do?
Function | Description |
Implantation | Thickens the uterine lining for a fertilized egg to implant. |
Menstruation | Helps regulate bleeding during menstruation. |
Pregnancy | Supports a pregnancy after conception. |
Mood | May help improve mood. |
Thyroid | Supports thyroid function. |
Lactation | Supports lactation. |
How does the body produce progesterone?
The corpus luteum produces progesterone after ovulation. It is a temporary gland that develops from the empty egg follicle after the ovary releases an egg. After conception and fertilization, it helps maintain progesterone levels to support a pregnancy. The adrenal glands and placenta also produce progesterone. [1]
Production site | When or how it contributes |
Corpus luteum | Produces progesterone after ovulation and supports early pregnancy if conception occurs. |
Adrenal glands | Also make progesterone. |
Placenta | Takes over progesterone production once it forms during pregnancy. |
What are normal progesterone levels?
Progesterone levels fluctuate throughout the menstrual cycle. They rise after ovulation and continue to rise if pregnancy occurs. A healthcare professional is the best person to determine what a progesterone level should mean based on where a person is in the menstrual cycle or whether they are pregnant. A single result should not be interpreted without its timing and clinical context.
What are symptoms of low progesterone?
Low progesterone can affect the body and may cause noticeable symptoms. If a person is not pregnant, symptoms can include irregular menstrual periods, difficulty conceiving, mood changes, anxiety or depression, trouble sleeping and hot flashes. These symptoms can have many possible causes and do not establish that progesterone is low.
Low progesterone during pregnancy
Progesterone helps maintain the uterine lining so a fetus can grow. Low levels during pregnancy may make it difficult to stay pregnant and are associated with ectopic pregnancy, miscarriage and preterm labor. Contact a healthcare professional for spotting or cramping during pregnancy.
What are symptoms of high progesterone?
High progesterone levels do not typically have a negative effect on health. In rare cases, high levels can be a sign of ovarian or adrenal cancer. An unexpected result needs professional interpretation, because an online article cannot determine whether a level is clinically important or what caused it.
How is progesterone tested?
A blood test, sometimes called a PGSN or progesterone test, can measure progesterone levels. It is most commonly used to determine ovulation. Because progesterone changes throughout the cycle and during pregnancy, the timing of the test matters. A healthcare professional can explain how the result relates to cycle timing or pregnancy.
Question | Answer |
What test is used? | A blood progesterone or PGSN test. |
Common use | Determining ovulation. |
Why does timing matter? | Progesterone fluctuates throughout the cycle and rises after ovulation. |
Who interprets it? | A healthcare professional, using cycle timing and pregnancy status. |
When might a healthcare professional prescribe progesterone?
Some women may need progesterone supplements. A healthcare professional may prescribe progesterone for perimenopause symptoms, menstrual-cycle regulation or pregnancy prevention through the minipill. Treatment decisions depend on the person's symptoms, health history, reproductive goals, pregnancy status and other clinical factors. Do not start, stop or change hormone treatment without professional guidance.
How does progesterone change during perimenopause?
During the transition to menopause, the ovaries no longer produce high levels of estrogen and progesterone, and changes in these hormone levels can cause symptoms. Symptoms can include hot flashes, night sweats or cold flashes, vaginal dryness and discomfort during sex. To learn more, see our guides to perimenopause and menopause.
A healthcare professional may recommend estrogen-progesterone hormone therapy, also called combination therapy, to relieve these symptoms.
Does progesterone cause weight gain or tiredness?
Weight gain is not a direct side effect of progesterone. Although hormones in general can affect hunger and weight, too much or too little progesterone alone is not usually a cause of weight gain. Low progesterone levels may make a person feel more tired.
What is the difference between progesterone and progestin?
Progestin is a synthetic form of progesterone created in a laboratory. A healthcare professional may use it when the body is not producing enough progesterone. It is available as pills, vaginal gels, injections and intrauterine devices, and it may be used for birth control, hormone replacement therapy, abnormal vaginal bleeding, irregular menstruation or certain cancers.
The terms are related but not identical: progesterone is a hormone produced by the body, while progestin refers to synthetic forms.
How does progesterone work with estrogen?
Progesterone and estrogen work together to regulate processes such as menstruation. When progesterone is low, estrogen may dominate and body processes may become less regulated. Possible effects include irregular periods, breast tenderness, depression or mood changes, gallbladder issues and low libido. The two hormones also work together in combination hormone-replacement therapy for menopause symptoms and in certain oral contraceptives to prevent pregnancy.
Can foods naturally increase progesterone?
Research is limited, but foods rich in zinc, vitamin C, B vitamins and magnesium may help support healthy progesterone levels, though food cannot guarantee higher progesterone.
Zinc: beef, shellfish, cashews, chickpeas, lentils and eggs.
Vitamin C: citrus fruits, peppers, strawberries and broccoli.
Vitamin B: carrots, spinach, walnuts and poultry.
Magnesium: green vegetables, nuts, seeds and beans.
Food is not a guaranteed way to raise progesterone, and these examples are not a substitute for evaluation or treatment.
When should you contact a healthcare professional?
Contact a healthcare professional for irregular periods, difficulty conceiving, or questions about progesterone levels. Contact a provider for spotting or cramping during pregnancy. Seek prompt pregnancy care for bleeding, cramping or other concerning symptoms. Call 911 or go to the emergency room for heavy bleeding, severe belly or pelvic pain, shoulder-tip pain, dizziness or fainting in pregnancy, because these can be signs of an ectopic pregnancy.
Conclusion: Progesterone changes with the reproductive timeline
Progesterone helps prepare the uterine lining for implantation, supports menstruation and helps maintain early pregnancy. After ovulation, the corpus luteum produces it; during pregnancy, the placenta eventually takes over. Levels rise after ovulation and change throughout pregnancy, so test results depend on timing and context.
Low levels can be associated with reproductive symptoms and pregnancy complications, while high levels are not usually harmful but can rarely signal an underlying condition. Use this guide to prepare questions for a qualified healthcare professional. Clear hormone information is a starting point for better care, not a diagnosis.
Frequently Asked Questions
What is progesterone?
Progesterone is a hormone involved in the reproductive system. It supports menstruation and the early stages of pregnancy.
What is progesterone's main function?
Progesterone prepares the uterine lining for a fertilized egg to implant and grow.
When does progesterone rise?
Progesterone rises after ovulation and continues to rise if pregnancy occurs.
What happens to progesterone if pregnancy does not occur?
The corpus luteum breaks down, progesterone decreases and the uterine lining thins and sheds during menstruation.
Who produces progesterone?
The corpus luteum produces it after ovulation. The adrenal glands and placenta also make it, and the placenta takes over production once it forms during pregnancy.
What does progesterone do during pregnancy?
Progesterone thickens the uterine lining, prevents ovulation, suppresses uterine contractions and helps the breasts prepare for breastfeeding.
What are symptoms of low progesterone when not pregnant?
Symptoms can include irregular periods, difficulty conceiving, mood changes, anxiety or depression, trouble sleeping and hot flashes.
Can low progesterone affect pregnancy?
Low progesterone is associated with ectopic pregnancy, miscarriage and preterm labor.
Are high progesterone levels dangerous?
High levels do not typically have a negative impact, but rarely they can indicate ovarian or adrenal cancer. Unexpected results need professional interpretation.
How is progesterone tested?
A blood test, also called a PGSN or progesterone test, can measure it and is most commonly used to determine ovulation.
What are normal progesterone levels?
Levels fluctuate throughout the menstrual cycle, rise after ovulation and continue to rise if pregnancy occurs. A healthcare professional should interpret a result based on cycle timing or pregnancy status.
Does progesterone cause weight gain?
Weight gain is not a direct side effect of progesterone. Too much or too little progesterone alone is not usually a cause of weight gain.
Can low progesterone cause tiredness?
Low progesterone levels may make a person feel more tired.
What is progestin?
Progestin is a synthetic form of progesterone made in a laboratory. It may be used for birth control, hormone replacement therapy, abnormal bleeding, irregular menstruation or certain cancers.
What symptoms can occur during perimenopause?
Symptoms can include hot flashes, night sweats or cold flashes, vaginal dryness and discomfort during sex.
Can food increase progesterone?
Research is limited. Foods containing zinc, vitamin C, vitamin B and magnesium may help support healthy progesterone levels, but food is not a guaranteed treatment.
When should I contact a healthcare professional?
Contact one for irregular periods, difficulty conceiving, questions about hormone results, or spotting or cramping during pregnancy.
Related Reading
Low Progesterone: Understanding Its Role in Menstruation and Pregnancy explains the signs and causes of low progesterone.
Understanding Progestin: Synthetic Support for Hormonal Balance describes lab-made progesterone used in birth control and hormone therapy.
Threatened Miscarriage: Symptoms, Causes, Tests, and Care explains bleeding in early pregnancy and how it is evaluated.
Understanding Human Chorionic Gonadotropin (hCG): The Pregnancy Hormone covers the pregnancy hormone that supports progesterone production early on.
References
Cleveland Clinic. Progesterone: Natural Function, Levels & Side Effects. Cleveland Clinic. Updated December 29, 2022. https://my.clevelandclinic.org/health/body/24562-progesterone
Coomarasamy A, Devall AJ, Cheed V, et al. A Randomized Trial of Progesterone in Women with Bleeding in Early Pregnancy. N Engl J Med. 2019;380(19):1815-1824. PMID 31067371. https://doi.org/10.1056/NEJMoa1813730
Romero R, Conde-Agudelo A, Da Fonseca E, et al. Vaginal progesterone for preventing preterm birth and adverse perinatal outcomes in singleton gestations with a short cervix: a meta-analysis of individual patient data. Am J Obstet Gynecol. 2018;218(2):161-180. PMID 29157866. https://doi.org/10.1016/j.ajog.2017.11.576
Disclaimer
This article is for general educational purposes and is not a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified healthcare professional with any questions about a medical condition or treatment.
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