The endometrium of 5mm on the tenth day of menstruation is generally normal. On the tenth day of menstruation, the follicle in the ovary gradually develops and grows, but at this time the level of estrogen in the body is still relatively low, the endometrium is gradually thickened under the action of estrogen, and at this time, the female endometrium is generally in the range of 4~8mm, so the endometrium thickness of 5mm may be normal. The thickness of the endometrium will change with the changes of the menstrual cycle, the endometrium is the thinnest after the menstrual period, usually less than 4mm, the thickest before the onset of menstruation, usually 10~12mm, and at the same time, because the endometrium is the material basis for the menstrual blood flow, so the endometrium is thin, then the amount of menstruation will be small. For women with abnormal endometrial thickness, it is recommended that they go to the gynecology department of a regular hospital to improve ultrasound, sex hormones and other relevant examinations, and then take active treatment under the guidance of the doctor after clarifying the cause of the disease.