Please consult a medical professionaland then even more importantly, pay attention to what you're feeling. You might need to adjust your medicine, if you use any, in order to avoid seriously dangerous low blood-sugar levels.
(I used to fast frequently, didn't have to much difficulty doing so, and could do so for up to three days without discomfort, and five before I felt I really had to do something else to maintain health. Now that I'm on metformin and a long-acting insulin analogue, nix to all of those. If I'm going to fast a day, the metformin is out, and the insulin analogue is cut by about half, otherwise I get massive headaches and my blood-sugar levels swing to dangerous levelsbut you mileage will likely vary.)
Any sufficiently advanced technology is indistinguishable from a rigged demo. - Andy Finkel, computer guy