Progesterone is a hormone responsible for fertility and menstruation.

A structure of cells within the ovaries called the corpus luteum secretes progesterone. If the body does not produce enough, there is a risk of:

  • pregnancy loss
  • preterm birth
  • ectopic pregnancy

Progesterone prepares the endometrium, the innermost lining of the uterus, for pregnancy. The hormone helps thicken this lining to support implantation.

If pregnancy occurs, the body and the placenta continue to release progesterone to support the growing fetus. Levels of the hormone continue to rise throughout pregnancy.

Though doctors understand the importance of progesterone in females, they know little about the hormone’s role in males.

In this article, we explore the symptoms of low progesterone and the treatment options.

Females with low progesterone may have irregular periods.

For those interested in becoming pregnant, it may be difficult. Without enough of this hormone, the body cannot prepare the right environment for the egg and developing fetus. If someone with low progesterone becomes pregnant, there may be an increased risk of pregnancy loss.

Signs of low progesterone include:

  • abnormal uterine bleeding
  • irregular or missed periods
  • spotting and abdominal pain during pregnancy
  • recurrent pregnancy loss
  • early labor
  • ectopic pregnancy

A 2018 study found that low progesterone may lead to more severe symptoms relating to the menstrual cycle, including:

  • mood changes
  • anxiety
  • depression
  • weight gain, bloating, and swelling due to fluid retention
  • breast tenderness

Also, changes in progesterone levels may lead to migraine. As the authors of a different 2018 study note, doctors often do not prescribe birth control pills containing estrogen to people who have migraine. They suggest that taking a progestin-only birth control pill might help manage this condition.

Progestin is the synthetic form of progesterone in medical treatments.

Does low progesterone cause hot flashes?

Experts do not know what causes hot flashes. Low estrogen levels likely play a role, but there is no evidence that low progesterone is a cause.

Progesterone may help manage hot flashes, although experts say that estrogen therapy is more effective. The American College of Gynecologists only recommends estrogen therapy. Progestin therapy might be helpful for those who cannot have estrogen therapy.

Low progesterone and high estrogen

Since estrogen and progesterone work together to regulate fertility and the menstrual cycle, low progesterone levels may cause estrogen levels to rise.

Someone with high estrogen may experience:

  • decreased libido
  • weight gain
  • gallbladder issues

Progesterone is a steroid hormone that the body produces in the:

  • adrenal cortex, the outer region of the adrenal glands, which sit above the kidneys
  • the ovaries and testes
  • the ovarian corpus luteum during the first 10 weeks of pregnancy

Causes of low progesterone include:

Conditions related to low progesterone levels include:

Chronic anovulation

If a person’s menstrual cycle is longer than 32–35 days, they may not be ovulating. This is known as anovulation. A doctor can measure progesterone levels to diagnose it.

Infertility

Even when a menstrual cycle is regular, ovulation might not occur, and doctors should check for low progesterone levels.

Endocrine Society guidelines recommend screening all females for ovulation dysfunction.

Preterm birth

Researchers suggest that preterm birth may occur when progesterone levels are low.

Progesterone might help maintain the uterus during pregnancy by blocking factors that cause preterm delivery. In some cases, pregnant people need hormone supplementation.

Menopause

Some people take hormone replacement therapy to reduce menopause symptoms.

Those taking estrogen therapy for this purpose, and who have not had a hysterectomy, must also take progesterone supplements to help prevent uterine cancer.

A blood test can tell someone’s progesterone levels.

Throughout different stages of the menstrual cycle, progesterone levels fluctuate. During the first half of the cycle, called the follicular phase, progesterone levels are under 1.5 nanograms per milliliter (ng/ml) of blood.

Just before ovulation, this level increases. It then rises again within a week after ovulation.

Throughout pregnancy, doctors measure progesterone levels to track how the corpus luteum and placenta are working.

During the first trimester, maternal progesterone increases slowly, to around 40 ng/ml.

Between weeks 6–8, doctors consider low progesterone levels to be less than 10 ng/ml, which is a sign of an abnormal or ectopic pregnancy.

In the remaining trimesters, progesterone levels continue to increase to 150 ng/ml.

After menopause, they fall below 0.5 ng/ml.

Although a blood test can detect low progesterone, doctors may need to carry out further tests to diagnose the cause.

Females with low levels of progesterone may require supplementation. Depending on the cause, doctors prescribe different forms of the hormone. They also consider the risk of side effects.

For example, some people cannot tolerate side effects of oral progesterone and may receive the hormone as a topical cream or gel.

To prevent preterm birth, doctors may recommend vaginal progesterone or intramuscular injections.

People taking hormone replacement therapy for menopause symptoms may also require progesterone supplementation.

In some cases, fertility specialists may prescribe progesterone suppositories.

Anyone who notices symptoms of low progesterone, such as irregular periods, may wish to speak to a doctor if they are concerned and trying to conceive.

A doctor may refer them to a specialist in female reproductive health, a gynecologist, or hormone specialist, an endocrinologist.

If a person is younger than 35 and trying to become pregnant, experts recommend only consulting a fertility specialist after 12 months of trying to conceive naturally. Anyone older than 35 may wish to speak to a doctor earlier.

Females with low progesterone levels may have irregular periods and difficulty conceiving.

Blood tests can detect low levels of the hormone, and further tests can help determine the underlying cause.

To restore progesterone levels, doctors may prescribe different forms of the hormone. The right treatment depends on the cause and takes into account the potential side effects.

Anyone who suspects that they have low progesterone levels should consult a doctor.