The 4 phases of the menstrual cycle, explained simply

Your menstrual cycle is about much more than your period. Every month, a finely tuned conversation between your brain and ovaries prepares your body for a possible pregnancy, then starts again if pregnancy doesn’t happen. Understanding the four phases of the menstrual cycle can help you make sense of changes in your energy, mood, skin and appetite, and makes it easier to notice when something seems off.

What is a menstrual cycle?

A cycle starts on day 1, the first day of your period (real bleeding, not just spotting), and ends the day before your next period begins. The average cycle lasts around 28 days, but very few people run like clockwork. For adults, anything between 21 and 35 days is considered normal, and it’s common for your cycle to vary by a few days from month to month. In the first years after your first period, cycles are often longer and less predictable.

The four hormones behind your cycle

Four main hormones run the show. Here’s what each one does:

• FSH (follicle-stimulating hormone) comes from the pituitary gland in your brain. It tells your ovaries to start maturing follicles, tiny fluid-filled sacs that each contain an egg.
• Estrogen is produced by the growing follicles. It rebuilds the lining of your uterus after your period and, as it rises, often lifts energy and mood.
• LH (luteinizing hormone) surges when estrogen peaks. This surge triggers ovulation, the release of a mature egg.
• Progesterone is made after ovulation by the corpus luteum, what remains of the follicle that released the egg. It stabilizes the uterine lining and slightly raises your body temperature.

The four phases, step by step

1. Menstrual phase (around days 1 to 5)

If no pregnancy occurred in the previous cycle, estrogen and progesterone fall and the lining of your uterus is shed: that’s your period. Bleeding usually lasts 2 to 7 days. Chemicals called prostaglandins make the uterus contract to push the lining out, which is why cramps are common in the first days.

2. Follicular phase (from day 1 until ovulation)

The follicular phase technically starts on day 1 as well, overlapping with your period, and lasts until ovulation. FSH encourages several follicles to grow, and usually one becomes dominant. Rising estrogen thickens the uterine lining again. This phase varies the most in length, which is why your whole cycle can be shorter or longer from one month to the next.

3. Ovulation (one day, around mid-cycle)

When estrogen is high enough, your brain releases a surge of LH, and within about 24 to 36 hours the dominant follicle releases its egg. The egg survives for only 12 to 24 hours. Ovulation usually happens 12 to 16 days before your next period, so the famous “day 14” only applies to an average 28-day cycle. The days just before ovulation, plus ovulation day itself, make up your fertile window.

4. Luteal phase (from ovulation until your next period)

The empty follicle becomes the corpus luteum and produces progesterone, which prepares the uterine lining for a possible pregnancy. This phase is fairly stable and usually lasts about 12 to 16 days. If the egg isn’t fertilized, the corpus luteum breaks down, hormone levels drop, and your next period begins, bringing you back to day 1.

How you might feel in each phase

Everyone is different, and sleep, stress and health matter too, but many people notice patterns like these:

• Menstrual phase: energy may dip, and cramps, back pain or tiredness are common. Some people also feel relief as premenstrual tension fades.
• Follicular phase: as estrogen climbs, many people feel more energetic, sociable and motivated, and skin often looks clearer.
• Ovulation: energy and libido often peak. You may notice clear, stretchy discharge or a brief twinge on one side of your lower belly.
• Luteal phase: progesterone can make you feel calmer or sleepier. In the last few days, falling hormones may bring bloating, breast tenderness, cravings, irritability or breakouts, the familiar signs of PMS.

Why tracking your cycle helps

Noting when your period starts and how you feel each day turns vague impressions into useful information:

• Plan ahead: know roughly when your next period is due.
• Understand yourself: spot recurring patterns in mood, energy, sleep or skin, and go easier on yourself on tougher days.
• Know your fertile window: useful whether you hope to get pregnant or simply want to understand your body.
• Notice changes early: a shift in cycle length, heavier bleeding or new pain stands out when you have a record.

When to see a doctor

Cycles vary, and an occasional early or late period is rarely a cause for concern. But some changes deserve a check-up.