It is recommended to avoid taking it during menstruation. This is the information I found in the Dong'a Colla Corii Asini: Colla Corii Asini is a blood tonic, stopping the blood of the holy medicine, for women because of blood deficiency caused by irregular menstruation has a very good recovery regulating effect. Some people take Colla Corii Asini during menstruation to regulate menstruation with better effect, while some people may take it to cause early or late menstruation or changes in menstruation volume. Therefore, it is recommended that women take a small amount during menstruation, if there is an effect on menstruation, stop taking it, no effect can be taken.