A menstrual cycle has four distinct phases: menstruation, 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 phase is driven by shifting hormone levels that prepare the body for a possible pregnancy, then reset when pregnancy doesn’t occur.
Phase 1: Menstruation
Menstruation is the phase most people think of as “the period.” It starts on day 1 of the cycle, when the lining of the uterus sheds because no fertilized egg implanted during the previous cycle. Most periods last between three and seven days. Total blood loss during a normal period is under 60 milliliters, roughly four tablespoons. Losses above 80 milliliters are considered excessive and worth bringing up with a doctor.
Hormone levels, especially estrogen and progesterone, are at their lowest point during menstruation. That dip affects serotonin, a brain chemical tied to mood, which is why this phase often comes with cramps in the lower belly or back, headaches, bloating, breast tenderness, poor sleep, and low energy. Mood swings and feeling easily irritated or sad are common too. Once bleeding tapers off, most of these symptoms start to ease.
Phase 2: The Follicular Phase
The follicular phase technically overlaps with menstruation. It begins on day 1 and runs until ovulation, roughly the first 14 days of a 28-day cycle. During this stretch, the pituitary gland releases a hormone that signals the ovaries to start developing egg-containing sacs called follicles. Between 11 and 20 follicles begin maturing, but only one will go the distance.
That single “dominant” follicle outpaces the others and pumps out increasing amounts of estrogen. The rising estrogen does two things at once: it thickens the uterine lining (which grows to about 12 to 13 millimeters, roughly half an inch) and it signals the brain to dial back the hormone that started the process. Without that stimulation, the remaining follicles wither and get reabsorbed by the body.
This is when most people start feeling noticeably better. Energy climbs, sleep improves, bloating fades, and motivation picks up. Many people notice a surge of confidence and a higher sex drive toward the end of this phase, right before ovulation.
Phase 3: Ovulation
Ovulation is the shortest phase, lasting roughly 24 hours. In a 28-day cycle it happens around day 14, triggered by a sharp spike in luteinizing hormone (LH). That LH surge begins about 36 hours before the egg is released and peaks 8 to 20 hours before ovulation itself. This is the window that ovulation test kits detect: a positive result means the egg will likely release within 12 to 48 hours.
Once the dominant follicle ruptures, the egg travels into the fallopian tube, where it can be fertilized for roughly 12 to 24 hours. Body temperature rises slightly after ovulation, typically less than half a degree Fahrenheit (about 0.3°C). That small shift is why tracking your temperature each morning can help confirm that ovulation occurred, though it only shows up after the fact.
Energy and confidence tend to peak around ovulation. Some people feel more social and outgoing. Mild cramping on one side of the lower abdomen is common and normal.
Phase 4: The Luteal Phase
The luteal phase spans roughly day 15 through day 28. After the egg leaves, the empty follicle transforms into a temporary structure called the corpus luteum. Its job is to produce progesterone, the hormone that prepares the uterine lining for a potential pregnancy. Under progesterone’s influence, the lining thickens further to about 16 to 18 millimeters.
If fertilization doesn’t happen, the corpus luteum starts breaking down about 10 days after ovulation. Progesterone and estrogen levels drop sharply, and the thickened lining loses its hormonal support. That triggers menstruation, and the cycle starts over.
The second half of the luteal phase is when premenstrual symptoms set in. Breast tenderness, bloating, food cravings, headaches, constipation, and trouble sleeping are all tied to the falling hormone levels. Emotionally, this phase can bring mood swings, anxiety, sadness, irritability, and fatigue. These symptoms are collectively what most people know as PMS, and they resolve once menstruation begins and hormones bottom out.
How Your Body Signals Each Phase
Beyond mood and energy, two physical markers track where you are in your cycle. Cervical mucus changes in a predictable pattern on a 28-day cycle:
- Days 1 to 4 (after bleeding ends): Dry or tacky, white or slightly yellow.
- Days 4 to 6: Sticky and slightly damp.
- Days 7 to 9: Creamy, like yogurt. Wet and cloudy.
- Days 10 to 14: Stretchy, slippery, and clear, resembling raw egg whites. This is the most fertile window.
- Days 15 to 28: Dries up again until the next period.
Basal body temperature follows a simpler pattern. It stays relatively low through the follicular phase, then bumps up slightly after ovulation and stays elevated through the luteal phase. If you’re tracking fertility or just want to understand your cycle better, pairing mucus observations with daily temperature readings gives a reasonably clear picture of when you ovulated.
What Counts as a Normal Cycle
The 28-day cycle is a useful reference point, but it’s not a rule. Cycles anywhere from 24 to 38 days are considered regular. What matters more than hitting an exact number is consistency. If your cycle is usually 32 days, that’s your normal. Variation of a few days from month to month is also expected, especially during the first few years of menstruation and in the years leading up to menopause.
Cycles shorter than 24 days or longer than 38 days fall outside the typical range. So do periods that suddenly become much heavier, much lighter, or stop altogether. These shifts can point to hormonal imbalances, thyroid issues, or other conditions that are worth investigating. Tracking your cycle length and symptoms for a few months gives you a personal baseline, which makes it much easier to spot when something changes.