The four stages of the menstrual cycle are the menstrual phase, the follicular phase, ovulation, and the luteal phase. A normal cycle lasts between 24 and 38 days, counted from the first day of one period to the first day of the next. Each stage is driven by shifting levels of four key hormones that prepare the body for a potential pregnancy, then reset when pregnancy doesn’t occur.
Phase 1: The Menstrual Phase
The menstrual phase is what most people simply call their period. It begins on day one of the cycle, when the lining of the uterus sheds because no fertilized egg has implanted. This happens because estrogen and progesterone have both dropped to low levels, removing the hormonal support that kept the lining in place. The top layers of the uterine lining, which had thickened with fluids and nutrients to nourish an embryo, break down and leave the body as menstrual blood. Bleeding normally lasts 4 to 8 days.
Beyond bleeding, this phase commonly brings cramps in the lower belly or back, bloating, breast tenderness, headaches, muscle aches, and low energy. Sleep quality often dips. Emotionally, mood swings and feelings of sadness or irritability are typical. These symptoms tend to be strongest in the first couple of days and ease as bleeding tapers off.
Phase 2: The Follicular Phase
The follicular phase overlaps with the menstrual phase because it also starts on day one, but it continues after bleeding stops and lasts until ovulation. This is the phase where your body selects and prepares an egg for release.
The pituitary gland in the brain releases follicle-stimulating hormone (FSH), which signals the ovaries to start developing follicles, the tiny fluid-filled sacs that each contain an immature egg. Around 11 to 20 eggs begin developing, but only one will fully mature. That single sac, called the dominant follicle, grows faster and larger than the rest and houses the healthiest egg.
As the dominant follicle matures, it releases increasing amounts of estrogen. By about day seven of the cycle, estrogen levels rise significantly. This estrogen does two things: it thickens the uterine lining (building up a nutrient-rich bed in case a fertilized egg needs to implant), and it signals the brain to slow down FSH production so the other follicles stop competing. The follicular phase is sometimes called the proliferative phase because the uterine lining is actively growing during this time.
Physically, most people notice a welcome shift during this phase. Energy increases, sleep improves, and bloating from the period fades. Many people feel more confident, motivated, and generally happier as estrogen climbs.
Phase 3: Ovulation
Ovulation is the shortest phase, centered around a single event: the release of a mature egg from the ovary. When estrogen reaches a high enough level, usually around day 13 of the cycle, it triggers a sudden spike of luteinizing hormone (LH) from the pituitary gland. This LH surge causes the dominant follicle to rupture and release its egg about 36 to 40 hours later.
The released egg travels into the fallopian tube, where it can potentially be fertilized by sperm. Your fertile window is about seven days total: the five days leading up to ovulation, the day of ovulation itself, and the day after. This window exists because sperm can survive in the reproductive tract for up to five days, while the egg is viable for a shorter time after release.
Some people feel ovulation happening. Common signs include mild cramping on one side of the lower abdomen, a slight rise in body temperature, and a change in vaginal discharge (it often becomes clearer and more slippery, similar to egg whites). Energy tends to stay high, and many people report feeling more social and confident around ovulation.
Phase 4: The Luteal Phase
After the egg leaves the follicle, the empty sac doesn’t just disappear. It transforms into a temporary structure called the corpus luteum, a yellowish mass of cells that forms where the follicle once was. The corpus luteum has one primary job: producing progesterone, the hormone that prepares the uterus for pregnancy.
Progesterone changes the uterine lining into a highly blood-vessel-rich environment where a fertilized egg could implant and grow. The corpus luteum also continues producing estrogen, so both hormones are elevated during this phase. Together, they maintain and stabilize the lining.
If the egg is fertilized and implants, the corpus luteum keeps producing progesterone to support the early pregnancy. If fertilization doesn’t happen, the corpus luteum breaks down, progesterone and estrogen levels drop sharply, and the uterine lining loses its hormonal support. That drop is what triggers shedding, and the cycle starts over with a new period.
The luteal phase is where premenstrual symptoms live. As progesterone rises and then falls, many people experience breast tenderness, bloating, food cravings, headaches, trouble sleeping, and digestive issues like constipation. Mood swings, anxiety, fatigue, and irritability are also common in the days before a period begins. The time between ovulation and the start of the next period can range from 7 to 19 days, though for most people it falls around 12 to 14 days.
How the Four Hormones Work Together
The entire cycle is orchestrated by four hormones working in sequence. FSH kicks things off by stimulating follicle growth in the ovaries. Estrogen rises as follicles develop, thickens the uterine lining, and eventually triggers the LH surge. LH causes ovulation. After ovulation, progesterone takes over, maintaining the uterine lining and creating conditions for implantation. When progesterone drops at the end of the luteal phase, the cycle resets.
These hormones don’t just affect the reproductive organs. They influence energy, mood, sleep, appetite, and body temperature throughout the month. The pattern explains why many people feel distinctly different at various points in their cycle: low energy during menstruation, rising confidence in the follicular phase, peak sociability around ovulation, and increased irritability or fatigue in the luteal phase. Tracking these patterns over a few months can help you anticipate how you’ll feel and plan around the natural rhythm of your cycle.