text: hyperventilation is breathing way too fast. Is she having this kind of symptom before she faints?  What kind of symptoms is she having? (besides fainting)  Fainting can be a symptom of so many things... low blood sugar, circulatory problems, blood pressure, pregnancy, and so on.  I bet if you googled  "fainting" or looked for a medical site that has a rundown of symptoms, you could better decide what is going on.  Seeing a regular doctor for a physical might help also, ER docs aren't the best resource for diagnosing complicated issues.