The menstrual cycle has four distinct phases: the menstrual phase, the follicular phase, ovulation, and the luteal phase. A full cycle typically lasts 21 to 35 days, counted from the first day of one period to the first day of the next. Each phase is driven by shifting levels of four key hormones, and understanding what happens in each one can help you recognize patterns in your own body.
The Menstrual Phase
Day one of your cycle is the first day of your period. This phase happens because no fertilized egg implanted during the previous cycle. Without a pregnancy to sustain, the structure that would have supported one (called the corpus luteum) breaks down, and estrogen and progesterone levels drop sharply. That hormonal withdrawal causes the thickened uterine lining to shed, which is the bleeding you experience.
Menstrual bleeding typically lasts 2 to 7 days. The flow consists of blood, tissue from the uterine lining, and fluid. Estrogen sits at its lowest point during this phase, which is why many people feel fatigued or low-energy during the first few days of their period.
The Follicular Phase
The follicular phase overlaps with menstruation and extends beyond it. It begins on day one of your cycle and lasts until ovulation, which makes it the longest and most variable phase. In a 28-day cycle, it typically runs about 14 days, but it can be shorter or longer depending on the person and the month.
Here’s what’s happening inside: your brain’s pituitary gland releases follicle-stimulating hormone (FSH), which signals your ovaries to start developing small fluid-filled sacs called follicles. Each follicle contains an immature egg. Several follicles begin growing at once, but one eventually outpaces the others and becomes the dominant follicle. That dominant follicle releases increasing amounts of estrogen, which does two important things. First, it thickens the uterine lining with blood and nutrients so it’s ready in case a fertilized egg needs to implant. Second, the rising estrogen actually signals the brain to decrease FSH production, which causes the remaining smaller follicles to wither away.
By about day seven, estrogen levels have risen significantly. You may notice changes in how you feel during this phase: energy and mood often improve as estrogen climbs. Cervical mucus also shifts. Right after your period ends, discharge tends to be dry or tacky and white. By the middle of the follicular phase, it becomes creamy and slightly wet, similar to the consistency of yogurt.
Ovulation
Ovulation is the shortest phase, lasting roughly 24 hours. It typically occurs around day 14 of a 28-day cycle, but the exact timing varies. The trigger is a dramatic spike in luteinizing hormone (LH), sometimes called the LH surge. When estrogen from the dominant follicle reaches a high enough level (usually around day 13), it causes a sudden release of LH from the pituitary gland. This surge begins about 36 hours before ovulation and lasts roughly 24 hours. The egg is released from the ovary 8 to 20 hours after LH reaches its peak.
Once released, the egg travels into the fallopian tube, where it can be fertilized for about 12 to 24 hours. This is the most fertile window of the cycle, though sperm can survive in the reproductive tract for several days, so the days leading up to ovulation are also fertile.
Your body gives noticeable signals around ovulation. Cervical mucus becomes stretchy, slippery, and clear, often compared to raw egg whites. This texture helps sperm travel more easily. Some people also feel a mild twinge of pain on one side of the lower abdomen when the egg is released.
The Luteal Phase
After the egg leaves the ovary, the empty follicle transforms into a temporary hormone-producing structure called the corpus luteum. This structure’s primary job is to pump out progesterone, along with some estrogen, to maintain and further prepare the uterine lining for a potential pregnancy. Progesterone makes the lining rich with nutrients and creates the right environment for an embryo to develop.
The luteal phase is more consistent in length than the follicular phase, lasting about 14 days in most people. If the egg is fertilized and implants in the uterine lining, the corpus luteum keeps producing progesterone through the first trimester of pregnancy. If no implantation occurs, the corpus luteum degenerates after about 14 days. Estrogen and progesterone levels fall, the uterine lining can no longer sustain itself, and menstruation begins again.
Progesterone is also responsible for the rise in basal body temperature (your resting temperature measured first thing in the morning) that occurs after ovulation. The increase is small, typically less than half a degree Fahrenheit, though it can range from 0.4°F to 1°F depending on the person. This temperature shift is one way to confirm that ovulation has already occurred. Cervical mucus during the luteal phase dries up noticeably, returning to a thick, dry, or almost absent state until your next period starts.
The late luteal phase is when premenstrual symptoms tend to show up. As progesterone and estrogen decline in the days before your period, you may experience bloating, breast tenderness, mood changes, or fatigue. These symptoms resolve once menstruation begins and the cycle starts over.
How to Track Your Cycle
You don’t need lab work to get a sense of where you are in your cycle. Two of the most practical markers are cervical mucus and basal body temperature. Mucus gives you a forward-looking signal: when it turns stretchy and egg-white-like, ovulation is approaching. Temperature gives you a backward-looking confirmation: a sustained slight rise means ovulation has already happened.
- Days 1 to 4 (menstrual phase): Bleeding. Mucus is not typically noticeable.
- Days 4 to 9 (early follicular): Mucus starts dry or tacky, then becomes sticky and slightly damp.
- Days 10 to 14 (late follicular into ovulation): Mucus is wet, slippery, and stretchy. This is your most fertile window.
- Days 15 to 28 (luteal phase): Mucus dries up. Basal body temperature is slightly elevated compared to the first half of the cycle.
These day ranges are based on a 28-day cycle and will shift if yours is shorter or longer. Tracking over several months gives you a clearer picture of your personal pattern.
What Counts as a Normal Cycle
A cycle length anywhere between 21 and 35 days falls within the normal range. Bleeding that lasts 2 to 7 days is also considered typical. Some variation from month to month is expected, especially during adolescence, perimenopause, or times of significant stress or weight change. Cycles that consistently fall outside the 21-to-35-day window, bleeding that lasts longer than seven days, or missing your period for 90 days or more are signs worth discussing with a healthcare provider.