The common causes of low menstrual flow after the onset of menstruation include: 1, excessive dieting and weight loss, long-term excessive dieting and weight loss of women, due to the reduction of subcutaneous fat, the loss of the function of fat cells to secrete estrogen, which affects the proliferation of the uterine lining, resulting in low menstrual flow. 2, irrational dietary structure, often partial, picky eaters, due to the imbalance of the intake of a variety of nutrients, so that the ovaries are deprived of nutrient The ovarian function declines prematurely, resulting in low menstrual flow.3. Poor mood, long-term depression, emotional irritability, overthinking women, will lead to dysfunction of the hypothalamus-pituitary-ovarian axis, causing low menstrual flow.4. Women who have been taking contraceptives for a long time, due to the suppression of normal endocrine function of the ovaries, will also cause low menstrual flow.5. Other endocrine system diseases. Hypothyroidism is the main endocrine system disease that causes low menstrual flow.