The menstrual cycle has four distinct phases: the menstrual phase, the follicular phase, the ovulatory phase, and the luteal phase. A normal cycle lasts between 24 and 38 days, though 28 days is often cited as typical. Each phase is driven by shifting hormone levels that prepare the body for a potential pregnancy, then reset if one doesn’t occur.
The Menstrual Phase
The cycle begins with your period. The lining of the uterus, no longer needed, sheds and flows out as a mix of blood, mucus, and tissue. A period typically lasts 3 to 7 days. During this time, estrogen and progesterone are at their lowest levels, which is why this phase often comes with the most noticeable symptoms: cramping in the lower belly or back, bloating, headaches, breast tenderness, muscle aches, and low energy. Sleep quality tends to drop, and mood swings or feelings of sadness and irritability are common.
Cervical mucus is minimal during this phase. You may notice a dry sensation once bleeding tapers off.
The Follicular Phase
The follicular phase overlaps with menstruation, starting on day one of your period and lasting roughly 13 to 14 days. While the uterine lining sheds, the brain’s pituitary gland ramps up production of follicle-stimulating hormone (FSH). This signals the ovaries to begin developing several small fluid-filled sacs called follicles, each containing an immature egg.
As the days progress, FSH levels taper and one follicle pulls ahead as the “dominant” follicle, while the rest stop growing. That dominant follicle starts producing estrogen, which does two important things simultaneously. In the uterus, rising estrogen triggers the lining to rebuild and thicken, a stage called the proliferative phase. All the cell types in the endometrium regenerate, and glands within the lining begin to develop. In the brain, rising estrogen sets the stage for the hormonal surge that will trigger ovulation.
This is when many people feel their best. Energy increases, sleep improves, bloating fades, and mood lifts. You may notice increased motivation and confidence as estrogen climbs.
The Ovulatory Phase
Ovulation is the shortest phase, lasting roughly 24 to 36 hours. It’s triggered when estrogen reaches a high enough level to cause a sharp spike in luteinizing hormone (LH), with a smaller rise in FSH. That LH surge signals the dominant follicle to release its mature egg into the fallopian tube.
The fertile window, however, is wider than ovulation itself. Sperm can survive inside the body for up to five days, while a released egg lives for less than 24 hours. The highest chance of conception occurs when sperm meets the egg within four to six hours of ovulation. This means the fertile window spans roughly six days: the five days before ovulation and the day of ovulation itself.
Signs of Ovulation
Your body gives a few signals around this time. Cervical mucus becomes transparent, stretchy, and slippery, often compared to raw egg white. This “egg-white” mucus helps sperm travel more easily. After ovulation, basal body temperature rises slightly, typically less than half a degree Fahrenheit (0.3°C). That temperature shift confirms ovulation has already happened, so it’s useful for tracking patterns over multiple cycles rather than predicting ovulation in real time.
Energy and confidence tend to peak during ovulation. Some people feel more social and outgoing. Mild cramping on one side of the lower abdomen is also common as the egg releases.
The Luteal Phase
After the egg is released, the empty follicle transforms into a temporary structure called the corpus luteum. Its primary job is producing progesterone, the hormone that shifts the uterine lining from a growth phase into a secretory phase. The lining stops thickening and starts producing nutrients and secretions designed to support a fertilized egg if one implants. Estrogen remains elevated during most of the luteal phase as well.
This phase lasts about 14 days with relatively little variation from cycle to cycle, making it the most consistent part of the menstrual cycle. If the egg isn’t fertilized, the corpus luteum begins to break down around 10 days after ovulation. As it degrades, progesterone and estrogen levels drop sharply, the uterine lining can no longer sustain itself, and a new period begins.
The hormonal drop in the late luteal phase is responsible for premenstrual symptoms. Breast tenderness, bloating, food cravings, constipation, trouble sleeping, and headaches are all common. Emotionally, you may experience mood swings, anxiety, fatigue, or irritability. These symptoms tend to intensify in the days just before your period and resolve once bleeding starts.
Why Cycle Length Varies
The 28-day cycle is a useful reference point, but cycles anywhere from 24 to 38 days are considered regular. Most of that variation comes from the follicular phase. Some cycles, the dominant follicle matures quickly; other cycles, it takes longer. Stress, illness, weight changes, and age can all affect how long this phase lasts. The luteal phase, by contrast, stays close to 14 days regardless of overall cycle length.
Cervical mucus patterns reflect this variability. After your period ends, you may notice several dry days followed by damp, then thick and creamy discharge (lower fertility), before the wet, slippery egg-white mucus appears near ovulation. Tracking these changes over a few months can help you recognize your own pattern, even if your cycle doesn’t land neatly on day 28.
How the Two Cycles Overlap
It helps to know that two cycles are actually happening at once. The ovarian cycle (what’s happening in your ovaries) and the uterine cycle (what’s happening in your uterus) run in parallel but are described with different terminology. The follicular phase of the ovarian cycle corresponds to the proliferative phase of the uterine cycle, when estrogen drives the lining to regrow. The luteal phase of the ovarian cycle corresponds to the secretory phase, when progesterone transforms the lining into a receptive environment for an embryo. The menstrual phase is the reset of both: the corpus luteum is gone, the lining sheds, and new follicles begin to develop.
Understanding this overlap explains why the same hormonal shift produces changes you can feel (energy, mood, cramping) and changes you can’t (lining thickness, gland development, follicle growth). Each symptom maps to a specific hormonal event, and the pattern repeats with each new cycle.