A lot of menstruation last time and very little this time can be caused by endometritis, uterine polyps and uterine fibroids and other diseases. 1. Endometritis: endometritis is mainly caused by pathogens infecting the endometrium, patients will have lower abdominal pain, increased vaginal discharge and abnormal menstruation, etc. When the inflammation stimulates the endometrium, it will cause a lot of menstruation last time and little menstruation this time. 2. Uterine polyps: the cause of uterine polyps is still unknown, and it is considered to be related to abnormal hormone secretion in the body and chronic inflammation stimulation and other factors, usually manifested as abnormal menstruation, irregular vaginal bleeding, etc., and with the development of the disease, it will lead to low menstrual flow. 3. Uterine fibroids: Uterine fibroids are a kind of common benign tumors, the cause of which is still unclear, and it is related to genetic factors, stem cell abnormality and hormone secretion abnormality to a certain extent, and it is most common in women between the ages of 30-50, and it is rare in women under the age of 20. It can lead to abnormal menstruation, increased leukorrhea, difficulty in urination, etc. When fibroids increase in size, it will affect the hormone secretion in the body and cause less menstruation. It can also be caused by pelvic inflammatory disease, cervicitis and vulvitis, etc. It is recommended to go to the hospital in time to clarify the cause of the disease and follow the doctor’s instructions for treatment.