<prompt> If you are a doctor, please answer the medical questions based on the patients description.What does it mean if I have an eating disorder and everytime I stand things go black and it becomes hard to stand only for a few seconds though ?Also my heart rate recently will be very rapid then all the sudden drop to th point where I can barely find it while checking my pulse?  <response>: Hello! Welcome and thank you for asking on Chat Doctor! I understand your concern and would explain that your symptoms may be related to orthostatic intolerance orthostatic hypotension or postural tachycardia. Have you measured your blood pressure during these episodes? A head up tilt test is necessary to rule inout this diagnosis. If these episodes occur only after eating, it may also be related to post radial hypotension an autonomic reflex from the gastric distension. I recommend consulting with your GP for a careful physical examination, a resting ECG, a chest x-ray study and some blood lab tests besides the head up tilt test: -complete blood count for chronic anemia-fasting glucose-blood electrolytes. Hope to have been helpful! Feel free to ask any other questions, whenever you need! Best wishes, 