The four phases

A typical adult cycle runs 21–35 days; in a study of 600,000+ cycles only about 13% were exactly 28 days. Here's a 28-day map — every body varies.

Days 1–5

Hormones are at their lowest and the uterine lining sheds. Energy often dips.

The science: Low estrogen and progesterone trigger shedding of the lining; prostaglandins cause cramps.

Days 6–13

Estrogen rises. Energy, mood and creativity climb.

The science: FSH grows follicles; the dominant one produces rising estradiol.

Days 14–16

Peak estrogen and testosterone. Confidence and social energy are high.

The science: An LH surge releases the egg about 24–36 hours later.

Days 17–28

Progesterone rises then falls. Cravings and PMS may appear.

The science: The corpus luteum makes progesterone, raising body temperature by ~0.3–0.5°C.