youre not gonna fool a doc by eating a banana, however for future reference, I used to be severely ill with an eating disorder (bulimic-anorexia) and I used to drink dioralyte after purging which was supposed to help electrolytes, it did make me feel somewhat better ( after youve had very low potassium you can usually feel the symptoms quite well ) it's not cheap but you can buy boxes of sachets from most pharmacies and it's better than a heart attack - although obviously your best option would be to recover (sorry to be preachy, but hey, coming from someone who's done it I gotta be honest)