It is best not to have a blood test during menstruation, as it has a greater impact on the body and may affect the normal test results.1. Women may experience dizziness, dysmenorrhea, anemia and other physiological manifestations during menstruation. If a blood test is performed at this time, it may lead to excessive blood loss, which may cause more serious anemia problems, and may also lead to more intense menstrual cramps, which may have a greater impact on the body. 2. When a blood test is performed, the hormone levels in the body may become disordered and endocrine disorders may directly lead to inaccurate blood results, so there may be errors in judgment. It is recommended that it is best not to perform physical examinations during menstruation, and not to perform strenuous exercise, so as not to cause some stimulation to the body, and if you want to perform physical examinations it is best to avoid the menstrual period.