During menstruation, blood tests are not allowed for the following reasons: 1. Because menstruation is a special physiological cycle for women, the content of estrogen, sex hormones, and follicle stimulating hormone increases significantly during this period. 2. During menstruation, the female body is in a relatively weak state and is sensitive to various stimuli. 3. Blood tests during the menstrual period may lead to menstrual disorders, so you should not take blood tests during the menstrual period.