The four phases of the menstrual cycle are menstruation, the follicular phase, ovulation, and the luteal phase. Together, they span roughly 28 days in a typical cycle, though anywhere from 21 to 35 days is normal. Each phase is driven by shifting levels of hormones that prepare the body for a potential pregnancy, then reset when pregnancy doesn’t occur.
Phase 1: Menstruation (Days 1 to 5)
Menstruation is the phase most people recognize: your period. It marks day 1 of the cycle. Over the previous weeks, the lining of your uterus thickened in preparation for a fertilized egg. When pregnancy doesn’t happen, levels of progesterone and estrogen drop sharply, and that now-thick lining sheds a little bit at a time over several days.
A typical period lasts 3 to 7 days. During this time, you may notice cramping in your lower abdomen as the uterus contracts to shed its lining. Energy levels tend to be lower, and some people experience headaches, fatigue, or lower back pain. Cervical mucus is minimal during and immediately after your period, and what’s there is usually dry or tacky with a white or yellowish tint.
Phase 2: The Follicular Phase (Days 1 to 13)
The follicular phase overlaps with menstruation, starting on day 1 and lasting until ovulation. It’s the most variable part of the cycle, which is why total cycle length differs so much from person to person. While menstruation handles the cleanup, the follicular phase is already building toward the next egg release.
Your pituitary gland (a small structure at the base of the brain) releases follicle-stimulating hormone, or FSH. FSH signals the ovaries to start developing follicles, which are fluid-filled sacs where eggs mature. Several follicles begin growing, but one becomes dominant and releases increasing amounts of estrogen. That rising estrogen does two things: it thickens the uterine lining so a fertilized egg could implant, and it eventually triggers the next phase.
As the follicular phase progresses, many people notice a gradual lift in energy and mood that tracks with rising estrogen. Cervical mucus also changes in a predictable pattern. In the days right after your period it’s sticky and white, then turns creamy and yogurt-like around days 7 to 9, and finally becomes stretchy, slippery, and similar to raw egg whites as you approach ovulation. That egg-white consistency is one of the clearest signs that ovulation is near.
Phase 3: Ovulation (Around Day 14)
Ovulation is the shortest phase, lasting roughly 24 hours. It happens when estrogen levels climb high enough to trigger a surge of luteinizing hormone (LH). About 36 to 40 hours after that LH surge, the dominant follicle ruptures and releases a mature egg into the fallopian tube.
The egg survives for about 12 to 24 hours after release. Because sperm can live in the reproductive tract for up to five days, the fertile window stretches from about five days before ovulation through the day of ovulation itself. This is the only window in the cycle when conception can happen.
Some people feel ovulation as a brief, one-sided twinge or mild cramp in the lower abdomen. You might also notice light spotting. Cervical mucus is at its most slippery and stretchy during this phase. After ovulation, your basal body temperature (your temperature first thing in the morning before getting out of bed) rises slightly, typically less than half a degree Fahrenheit, though the increase can range from 0.4°F to 1°F. That temperature shift is driven by progesterone and confirms ovulation has already occurred, making it useful for tracking but not for predicting it in real time.
Phase 4: The Luteal Phase (Days 15 to 28)
Once the egg leaves the follicle, the empty sac transforms into a new structure called the corpus luteum, a yellowish mass of cells that takes over hormone production. Its primary job is releasing progesterone, which converts the uterine lining into an environment that could support a pregnancy. The corpus luteum also produces some estrogen.
The luteal phase is the most consistent part of the cycle. It averages 12 to 14 days, with a normal range of 10 to 17 days. A luteal phase shorter than 10 days can be a problem for fertility because the uterine lining doesn’t have enough time to thicken sufficiently for an embryo to implant.
If a fertilized egg implants, it releases a hormone called hCG that keeps the corpus luteum alive and producing progesterone through early pregnancy. If implantation doesn’t happen, the corpus luteum breaks down, progesterone and estrogen plummet, and the cycle resets with menstruation.
PMS and the Luteal Phase
The late luteal phase is when premenstrual symptoms show up, typically in the week or two before your period. The physical symptoms are familiar to most people: bloating, breast tenderness, fatigue, headaches, acne flare-ups, joint or muscle pain, and constipation or diarrhea. Weight can increase slightly from fluid retention.
The emotional side is just as real. Common experiences include irritability, mood swings, anxiety, food cravings, difficulty concentrating, trouble sleeping, and lower motivation to socialize. These symptoms are linked to the hormonal shifts as progesterone peaks and then drops. For a smaller percentage of people, a more severe form called PMDD causes intense depression, anger, or anxiety that significantly interferes with daily life.
After your period, cervical mucus becomes dry or nearly dry for the remainder of the luteal phase, staying that way until menstruation starts again.
How the Phases Connect
The four phases aren’t isolated events. They’re a feedback loop. Estrogen rising in the follicular phase triggers the LH surge that causes ovulation. The leftover follicle becomes the corpus luteum, which produces progesterone to sustain the uterine lining. When the corpus luteum dies, falling progesterone triggers menstruation, and the drop in hormones signals the pituitary gland to release FSH again, starting a new follicular phase.
Cycle length varies mostly because the follicular phase varies. Stress, illness, significant weight changes, and intense exercise can all delay ovulation, stretching the follicular phase and making your cycle longer that month. The luteal phase, by contrast, stays relatively fixed. So if your cycle is unusually long or short, the follicular phase is almost always what shifted.