What Is Progesterone?

Young pregnant woman touching her belly
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Progesterone is commonly referred to as the pro-gestational hormone or the “pregnancy hormone” because of its role in creating an ideal environment for conception and sustaining early pregnancy.

Before a woman becomes pregnant, progesterone helps prepare the uterus for implantation. After ovulation, a mass of cells called a corpus luteum forms on the ovary. The corpus luteum produces progesterone until the placenta takes over toward the end of the first trimester.

Women who are undergoing fertility treatments or are deficient in organically producing the hormone may be prescribed progesterone supplements. Let's explore progesterone's role when it comes to fertility and pregnancy, as well as how you can recognize the signs of low progesterone in your body.

Progesterone's Role Before Pregnancy

Progesterone levels dip during your period, which can leave you feeling fatigued and sluggish. During the next phase of your cycle, known as the follicular phase, progesterone rises to prepare your body for conception. The hormone promotes follicle development on your ovaries and helps thicken the uterine lining to support a potential pregnancy.

After ovulation, your body enters the luteal phase, which occurs between the time you ovulate until your next menstrual period. The corpus luteum begins producing progesterone during this phase. Progesterone levels will either continue to rise if you've conceived or will begin to decrease as your uterus prepares to shed its lining during your next period.

Progesterone also affects your breast tissue, which accounts for the sensitivity some women experience as a PMS symptom. It's not all in vain, though. Progesterone also stimulates your breast tissue during the luteal phase and prepares the breasts for milk production and lactation during pregnancy.

How Is Progesterone Measured?

Progesterone is measured in nanograms per milliliter (ng/mL). To better understand your levels, it's important to know what is considered an average range during your cycle.

Standard Progesterone Blood Test Ranges

  • 0.1 to 0.7 ng/mL in the follicular phase of the menstrual cycle
  • 2 to 25 ng/mL in the luteal phase of the menstrual cycle
  • 10 to 44 ng/mL during the first trimester of pregnancy

Factors such as age, health history, and certain medical conditions can impact your test results. If your doctor has ordered a serum progesterone test, be sure to discuss the results with your provider if you have questions regarding your hormone levels.

Progesterone's Role in Sustaining a Healthy Pregnancy

The importance of progesterone comes into play even before conception occurs. However, its role amps up from the time you conceive until about 10 weeks gestation when your placenta takes over progesterone production for the duration of the pregnancy. Progesterone also acts as an anti-inflammatory in the body, which helps protect women from miscarriage, late pregnancy loss, and early labor.

Women who have low levels of progesterone may be prescribed a supplement during pregnancy. Doctors typically recommend supplemental progesterone; this can be prescribed as a tablet, vaginal gel, or even intramuscular injection.

Possible Side Effects When Taking Synthetic Progesterone Include:

  • Bloating
  • Joint pain
  • Drowsiness
  • Depression
  • Breast tenderness
  • Abdominal cramping or pain
  • Dizziness
  • Headaches
  • Increased vaginal discharge
  • Hot flashes
  • Urinary problems

Supplements are generally prescribed through the end of the first trimester when the placenta kicks into gear but may be prolonged in certain cases. Women who have a history of preterm labor or premature rupture of membranes (PROM) may receive progesterone injections from the second trimester through week 36 to prevent an early delivery.

Symptoms of Low Progesterone

Progesterone is estrogen's important sidekick during a woman's childbearing years. Women with low levels of progesterone may have difficulty conceiving or maintaining a pregnancy.

It's easy to miss the signs of decreased progesterone levels before trying to conceive. Symptoms that indicate low progesterone include:

  • Migraines and headaches
  • Irregular menstrual cycles
  • Mood disorders, such as anxiety and depression

These symptoms don't necessarily point to this condition on their own. Still, it's worth speaking to your doctor about testing if you experience any of the above conditions without explanation.

Women who are not pregnant may experience abnormal vaginal bleeding or irregular periods. This can indicate the ovaries are not functioning properly, and low progesterone could be to blame.

Since estrogen and progesterone work hand-in-hand as female sex hormones, low progesterone levels mean estrogen is sent into overdrive. Increased estrogen levels can cause:

  • Decreased sex drive
  • Mood swings or worsening PMS symptoms
  • Irregular/heavy bleeding
  • Fibroids
  • Weight gain
  • Gallbladder issues

Treating Low Progesterone Levels

If you have low progesterone levels but are not experiencing adverse symptoms, you may not need treatment. However, women who are trying to conceive often benefit from hormone therapy to increase their chances.

Hormone therapy can also be beneficial in treating menstrual irregularities. Your doctor may first suggest natural remedies to increase progesterone levels.

Natural Ways to Increase Progesterone:

  • Increase your intake of B and C vitamins.
  • Manage your stress levels.
  • Eat foods that are rich in zinc.

Women who are at an increased risk for certain cancers, blood clots, or strokes are not typically candidates for hormone therapy. Doctors most often will not prescribe progesterone supplements to treat menopause symptoms, as low estrogen levels tend to be the cause. Speak to your provider about the safest options for treating your low progesterone levels.

A Word From Verywell

Progesterone plays a significant role before and during pregnancy. The hormone prepares the body for pregnancy by thickening the lining of the uterus, then works to sustain the pregnancy by producing the hormone through the corpus luteum.

Women with low levels of progesterone may experience difficulty conceiving or be at an increased risk for pregnancy loss. Treatment options are available for those who are suffering from low progesterone levels. These include natural remedies and hormone therapy.

If you suspect you have low progesterone levels, speak to your doctor about getting a progesterone test. This simple blood test requires no preparation and can provide you with answers about your condition. Your doctor will then guide you on the best treatment options available, which can be reevaluated as needed.

1 Source
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Kumar, P., & Magon, N. (2012). Hormones in pregnancy. Nigerian Medical Journal : Journal of the Nigeria Medical Association53(4), 179–183. doi:10.4103/0300-1652.107549

Additional Reading
  • Foley, Maryann. Haldeman-Englert, Chad. Turley, Raymond. Progesterone. Health Encyclopedia. University of Rochester Medical Center.

By Renee Plant
Renee Plant is a health and wellness freelance writer with a passion for delivering well-researched, factual content to readers.