Many women have heavy periods and this can be associated with low blood, tiredness and inability to carry out normal activities. Approximately 10-30% of these women will have an underlying bleeding disorder. There is a drug called tranexamic acid which is commonly used and is effective in reducing menstrual flow. However, up to 1/3 of women have side effects and they are more common at higher doses. In the medical literature, there are different dosing schedules and there is one commonly recommended in Canada. Women with underlying bleeding disorders may require higher doses of this medication compared to those who do not. In this study, the investigators want to find the lowest effective dose of tranexamic acid for girls and women with heavy periods who have bleeding disorders and the investigators think this will be lower then the usual recommended dose. If the investigators' results support this, it may contribute to changing how the investigators presently prescribe this medication and may provide a better option for women with heavy periods in particular those with bleeding disorders. The investigators have just started a Women with Bleeding Disorders Clinic and hope that this project will lead to better care for the patients and more research in the future.