The amount of menstruation may be related to the thickness of the endometrium. If it is thin, the amount of menstruation may be low; if it is thick, the amount of menstruation may increase suddenly on the second day. If you have eaten spicy food, including cold food, or have taken medication to promote blood circulation, it may cause a sudden increase in menstrual flow. If this happens simply once, you can observe it for a while. As long as it ends within 7 days or decreases slowly, it is not a big problem and will not affect your health. If pathological factors, such as fibroids, submucosal fibroids, endometrial hyperplasia, endometrial polyps, or endometrial lesions cause an increase in menstrual flow, an ultrasound should be performed 3 days after menstruation to determine if there are any adverse effects on the uterus, and oral medication should be taken to regulate the situation.