My husband had slightly high bp but his heart rate was way high so a year ago they put him on Atenalol (sp?) and its made it in a healthy range now. Some pain medications can lower blood pressure. When they thought I was having a heart attack (was anxiety) my bp was sky high and they pumped me up with morphine it brought it right back down. So maybe if youre normal and taking something that helps to lower it its making it low? Not sure!