If a woman’s endometrial thickness reaches 10mm, she will usually have her period in about 5 days, but it varies depending on her age, health, and the presence of underlying diseases. Generally speaking, the thickness of the endometrium determines the onset of menstruation. The endometrium will shed naturally when it reaches a certain thickness, and the shed endometrium is discharged to form menstruation. The thickness of the endometrium varies during different periods of menstruation. It is normal for the endometrium to be about 10mm before menstruation, and menstruation usually occurs in about 5 days. If the endometrium reaches 10mm for more than 7 days without menstruation, patients are advised to visit the hospital for a transvaginal ultrasound to check the thickness of the endometrium. If the endometrial lining is too thick, you need to take dydrogesterone or progesterone soft capsules to promote the shedding of the endometrial lining. Women should avoid spicy and stimulating foods during their periods, maintain a light diet, pay attention to hygiene, avoid strenuous exercise and maintain a good mood.