Blood tests can be drawn during menstruation, but the suitability of the patient’s tests to be performed during menstruation should be analyzed on a case-by-case basis. If only routine checkups are performed, such as blood count, liver and kidney function, blood sugar, etc., these tests are not any problem during menstruation. If the tests are related to blood sedimentation, the results may be affected during menstruation and the patient’s blood sedimentation rate will be accelerated. If the patient is having a sex hormone test, the time of the test should be chosen according to the patient’s test condition. When performing a basal sex hormone test, it is recommended that the test be performed during the menstrual period, with the blood drawn on an empty stomach 2-3 days after the onset of menstruation. If you want to check ovulation, such as luteinizing hormone and estrogen before ovulation, it is recommended that the test be performed before ovulation and not during menstruation. If you want to check the luteal function of the patient, it is recommended that the test be performed one week before your period and not during your period.