What Is Progesterone? Role in Cycle, Pregnancy & Symptoms

Hormones are powerful actors in your body, playing roles in everything from physical functions, to emotional regulation, to overall health.

Progesterone, a key reproductive hormone, is crucial for regulating your menstrual cycle, conceiving, and supporting a pregnancy.

So, what is progesterone? Read on to learn what this hormone is, what it does in your body, how progesterone fluctuates throughout your cycle and across different life stages, symptoms of low versus high progesterone, and how to track progesterone.

What is progesterone?

Progesterone is one of your central reproductive hormones. 

Alongside other reproductive hormones like estrogen, luteinizing hormone (LH), and follicle-stimulating hormone (FSH)—progesterone is an essential element to reproductive health and the menstrual cycle, across life stages.

Progesterone is produced by the:

• Ovaries: the glands where eggs are produced, located on either side of your uterus at the ends of the fallopian tubes
• Corpus luteum: a temporary gland formed after ovulation 
• Adrenal glands: hormone-producing glands above the kidneys

Want to understand the full cycle picture? Read: Progesterone: The Key Hormone in Your Cycle→

What does progesterone do?

Progesterone plays key roles in reproductive health, particularly in the menstrual cycle and pregnancy.

From cycle to cycle, progesterone helps regulate:

• Uterine lining (endometrium) growth
• Cycle regularity
• Period regularity
• Period flow

If you become pregnant in a given cycle, progesterone is essential for:

• Embryo implantation in the endometrium
• Embryo development
• Supporting the pregnancy
• Preventing miscarriage 
• Preparing the body for breastfeeding (or chestfeeding)

Progesterone isn’t just involved in reproductive health, though. This hormone also helps control functions throughout your body, including:

• Mood
• Thyroid function
• Energy levels
• Fatigue levels
• Bone health
• Heart health

Progesterone and the menstrual cycle

Progesterone helps control how regular your periods are, plus how heavy or how light your flow is. 

Levels of this hormone naturally fluctuate throughout your cycle, rising or falling depending on cycle phase. Here’s how.

Progesterone during the follicular phase

Your cycle starts with the follicular phase, on day 1 of your period. 

During this phase, you have your period and your body prepares for ovulation. Progesterone levels are low in the follicular phase.

Progesterone during the ovulatory phase

Around mid-cycle, ovulation occurs and your ovaries release a mature egg. If this egg gets fertilized, you can become pregnant.

The follicle that housed the egg prior to ovulation then becomes a corpus luteum. This temporary structure starts producing progesterone, making progesterone levels begin to rise.

The increase in progesterone signals the end of the ovulatory phase. It also confirms ovulation if progesterone doesn’t rise, it means you didn’t ovulate.

Progesterone during the luteal phase

Right after ovulation, you enter the second half of your cycle: the luteal phase.

During the luteal phase, progesterone levels are high. Rising progesterone makes the endometrium grow thick and full of nutrients, preparing the uterus for a potential pregnancy.

While progesterone naturally rises during the luteal phase and pregnancy, abnormally high levels can cause uncomfortable symptoms. Learn more about high progesterone symptoms: High Progesterone Symptoms: What They Mean→

Progesterone at the end of the menstrual cycle

What progesterone does at the end of a cycle, in the very late luteal phase, depends on whether or not you became pregnant in that cycle. 

If you’re not pregnant, progesterone levels drop back down. Then, you get your next period and the next cycle starts. 

If you are pregnant, progesterone stays elevated.

Progesterone during pregnancy

From conception to delivery, progesterone plays a major role in pregnancy. In fact, it’s sometimes called the pregnancy hormone.

For starters, progesterone is crucial for getting pregnant. Without progesterone, the endometrium doesn’t thicken properly. Without a thickened endometrium, the uterus isn’t prepared for a pregnancy, and a fertilized egg can’t implant and become an embryo.

Progesterone is also essential for supporting and maintaining a pregnancy. When you’re pregnant, progesterone continues to nourish the endometrium, which in turn supports the growing fetus. Progesterone also helps keep the uterus from contracting, which is part of what prevents miscarriages. 

During pregnancy, progesterone levels are high, increasing the further along you are.

Progesterone during perimenopause

Before reaching menopause, you first go through perimenopause, or the menopausal transition. Perimenopause can last several years, and may start anywhere from your mid-to-late 30s, to your early-to-mid (or even late) 40s—each person’s timeline is different. 

Perimenopause, a major, hormone-driven biological shift, triggers changes in your cycle, periods, and ovulation as you approach the end of your reproductive capabilities.

During perimenopause, progesterone fluctuates and declines overall. The decline isn’t steady, however. Instead, progesterone oscillates unpredictably from cycle to cycle (as do estrogen and LH), leading to uncomfortable, distressing, or even painful perimenopause symptoms.

Progesterone during menopause

You officially reach menopause once you’ve gone 12 consecutive months without a period.

At this point, progesterone stops fluctuating and stabilizes at its new baseline. This can bring symptom changes and even symptom relief. 

Post-menopause, progesterone is very low.

Low progesterone and high progesterone

Sometimes, progesterone may become low or high. But low or high compared to what? Well, your other hormones. 

Your hormones work together in a complex and intricate balance to make sure everything in your body functions properly. That balance naturally fluctuates as you move through your menstrual cycle, which can cause physical and emotional cycle symptoms.

If the balance is disrupted for a longer period of time, though, your hormones may be unable to do their job as intended. 

In this case, you may be dealing with a hormonal imbalance. A hormonal imbalance can trigger various symptoms, depending on which hormones are high and which are low. 

Low progesterone symptoms include:

• Irregular or missed periods
• Heavy periods
• Spotting between periods
• Fertility issues
• Recurrent miscarriages
• Breast tenderness
• Vaginal dryness
• Hot flashes
• Sleep disturbances
• Headache and migraine
• Anxiety

Get the complete guide: Low Progesterone Symptoms: Signs and Solutions→

High progesterone symptoms include:

• Irregular periods
• Bloating
• Weight gain
• Breast tenderness
• Acne
• Fertility issues
• Depressive symptoms 
• More severe PMS symptoms
• Fatigue

Consider talking with your doctor if you suspect you may be dealing with low progesterone or high progesterone. They can help you identify and manage any underlying issues.

How to track your progesterone levels

Measuring and tracking your progesterone levels enables you to follow cyclic changes and match symptoms with hormone fluctuations.

Multi-hormone test kits that measure progesterone, estrogen, and LH like the Oova fertility kit and app—are one great option for accurate, reliable, and easy at-home hormone tracking.

With Oova, you can monitor your cycle, track ovulation, decode your fertility, understand your perimenopause journey, plus use your hormone knowledge in your day-to-day life. This way, you can connect with your health and deepen your understanding of your body.

What is progesterone? The bottom line

Progesterone, a crucial reproductive hormone, is key to regulating the menstrual cycle, conceiving, and sustaining a pregnancy.

Progesterone levels naturally fluctuate in the span of a single cycle, and throughout your life from your reproductive years, to pregnancy, to perimenopause, to menopause.

Tracking your progesterone levels at home can help you take control of your health and fertility.

Frequently Asked Questions

What does progesterone do in simple terms?

Progesterone prepares your uterus for pregnancy after ovulation by thickening the uterine lining. If pregnancy occurs, it supports the developing fetus; if not, progesterone drops and you get your period.

When is progesterone highest in your cycle?

Progesterone is highest during the luteal phase (after ovulation), typically 7 days post-ovulation. Levels remain low during your period and before ovulation, then rise dramatically after an egg is released.

What are signs of low progesterone?

Signs of low progesterone include irregular or missed periods, heavy bleeding, spotting between periods, difficulty conceiving, recurrent miscarriages, anxiety, sleep disturbances, and hot flashes.

Does progesterone make you tired?

Yes, progesterone has a naturally calming effect and can cause fatigue, especially when levels are high during the luteal phase or pregnancy. This is why many women feel more tired in the second half of their cycle.

How does progesterone affect mood?

Progesterone produces allopregnanolone (ALLO), which has calming effects on the brain. However, when progesterone drops suddenly (like before your period), it can trigger anxiety, irritability, or depressive symptoms.

At what age does progesterone decline?

Progesterone begins declining during perimenopause, typically starting in your late 30s to mid-40s. After menopause (12 months without a period), progesterone stabilizes at very low levels.