Thank you for your query.
I am a bit confused by the diagnosis stated by you. Anorexia nervosa
cannot go together. Anorexia means no appetite whereas bulimia means forceful eating and purging. Repeated vomiting
can induce low potassium as it is lost with the vomitus. If vomiting is not the cause of low potassium then a thorough clinical and investigative workup is required to know the cause of low potassium level. In the interim you should take plenty of fresh fruit juice and/or banana to increase your potassium level.
I hope I have answered your query to your satisfaction.
Wishing you an early recovery.
Rajiv K Khandelwal