is the monthly shedding of the uterine lining (endometrium) that occurs in people with a uterus, typically starting during puberty (around ages 10–15) and continuing until menopause (around ages 45–55). It is a normal part of the menstrual cycle, which is controlled by hormonal changes that prepare the body for a possible pregnancy.
Key facts:
Duration – Usually lasts 3 to 7 days.
Frequency – Typically occurs every 21 to 35 days.
Flow – The blood and tissue exit through the cervix and vagina. The amount can vary from light to heavy.
Common symptoms – Cramps (lower abdomen), bloating, fatigue, breast tenderness, and mood changes.
Ovulation – Menstruation follows ovulation (release of an egg from the ovary). If the egg is not fertilized, hormone levels drop, triggering the uterine lining to shed.