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, with 28 days being the commonly cited average. Each phase is driven by shifting levels of hormones that prepare the body for a potential pregnancy, then reset when pregnancy doesn’t occur.
The Menstrual Phase (Days 1 to 7)
Your period marks day one of the cycle. The uterine lining that built up over the previous cycle sheds because no fertilized egg implanted. Most people lose about two to three tablespoons of blood over the course of their period, though bleeding can last anywhere from two to seven days.
Hormone levels are at their lowest point during this phase. That drop is what triggers the lining to break down in the first place, and it’s also why many people feel fatigued or moody in the first few days of their cycle. Energy tends to be low, sleep can feel less restorative, and cramps are common as the uterus contracts to shed its lining.
The Follicular Phase (Days 1 to 13)
The follicular phase actually overlaps with menstruation, starting on day one and lasting until ovulation. While you’re still bleeding, the brain’s pituitary gland is already releasing follicle-stimulating hormone (FSH), which signals the ovaries to start developing small fluid-filled sacs called follicles. Each follicle contains an immature egg.
Over the next several days, one follicle outpaces the rest and becomes the “dominant” follicle. As it matures, it releases increasing amounts of estrogen into the bloodstream. That rising estrogen does two things simultaneously: it thickens the uterine lining to prepare for a potential embryo, and it signals the pituitary gland to slow down FSH production. With less FSH circulating, the remaining follicles wither away and get reabsorbed by the body.
This is when most people start feeling noticeably better. As estrogen climbs, energy increases and mood tends to improve. Cervical mucus also begins to change. In the early follicular phase (right after your period), discharge is dry or tacky and white. By days seven to nine, it becomes creamy and cloudy, similar to yogurt in consistency.
Ovulation (Around Day 14)
Ovulation is the shortest phase, lasting roughly 24 hours. When estrogen from the dominant follicle reaches a critical threshold, it triggers a surge of luteinizing hormone (LH). About 36 to 40 hours after that LH surge begins, the dominant follicle ruptures and releases a mature egg into the fallopian tube.
The days surrounding ovulation are the fertile window. The egg itself survives only 12 to 24 hours after release, but sperm can live in the reproductive tract for several days, which is why the fertile window extends a few days before ovulation as well.
Your body gives a few observable signals around this time. Cervical mucus becomes slippery, stretchy, and clear, resembling raw egg whites. This texture helps sperm travel more easily. Basal body temperature (your resting temperature first thing in the morning) also rises slightly after ovulation, typically less than half a degree Fahrenheit. That temperature shift confirms ovulation has already happened, so it’s more useful for tracking patterns over multiple cycles than for predicting ovulation in real time.
The Luteal Phase (Days 15 to 28)
After the egg is released, the empty follicle transforms into a temporary structure called the corpus luteum. Its job is to produce progesterone, the hormone that stabilizes and maintains the uterine lining. Progesterone levels rise significantly during this phase, and the hormone is released in pulses that become more pronounced in the middle and late luteal phase. Levels can fluctuate up to eightfold within just 90 minutes.
If a fertilized egg implants in the uterine lining, it starts producing a hormone (hCG, the same one pregnancy tests detect) that keeps the corpus luteum alive and producing progesterone. The corpus luteum continues this role until the placenta develops enough to take over hormone production on its own.
If implantation doesn’t happen, the corpus luteum breaks down about 10 to 14 days after ovulation. Progesterone and estrogen levels drop sharply, the thickened uterine lining loses its hormonal support, and menstruation begins. The cycle resets to day one.
The luteal phase is when premenstrual symptoms are most common. Rising progesterone can cause bloating, breast tenderness, and mood changes. Cervical mucus dries up considerably after ovulation, becoming minimal or absent until your next period starts. Energy levels often dip in the final days as both estrogen and progesterone fall.
How Cycle Length Varies
The 28-day model is a useful reference point, but cycles between 21 and 35 days are considered normal. Most of that variation comes from the follicular phase, which can be shorter or longer depending on how quickly a dominant follicle develops. The luteal phase is more consistent, almost always lasting between 10 and 16 days.
Cycles shorter than 21 days or longer than 35 days, bleeding that lasts more than seven days, or cycles that are highly unpredictable from month to month may point to hormonal imbalances or other underlying conditions worth investigating. Stress, significant weight changes, intense exercise, and certain medications can all shift cycle timing without necessarily signaling a medical problem.
Tracking Your Phases
You don’t need lab work to get a rough sense of where you are in your cycle. Three markers you can observe at home give useful information when combined:
- Cervical mucus: Dry or sticky after your period, creamy in the mid-follicular phase, slippery and egg-white around ovulation, then dry again through the luteal phase.
- Basal body temperature: Stays relatively low through the follicular phase, then bumps up slightly after ovulation and remains elevated through the luteal phase. You need a thermometer accurate to one-tenth of a degree, and you need to measure before getting out of bed each morning.
- Period timing: Simply noting when your period starts each month reveals your cycle length and helps predict future phases.
Tracking for two or three cycles gives you a baseline. From there, you can start to notice patterns in energy, mood, and physical symptoms that correspond to each phase, which makes it easier to plan around them rather than be caught off guard.