Direct measurement of menstrual blood loss is the only reliable basis of the diagnosis 'menorrhagia'. We describe modifications of the alkaline hematin method for measuring menstrual blood loss (MBL) which improve the recovery rate from 89 to 98% and make the method more suitable for routine laboratory use. Using this modified method, 5 out of 21 patients (24%) complaining of menorrhagia and scheduled for hysterectomy had an MBL less than 80 ml, which is the upper level of normal MBL.