Furthermore, it proves to be very difficult to keep the level of the blood sugar low with insulin when diets are very rich in carbohydrate. The normal sugar level, as I have said, is 0.1 per cent. In uncontrolled diabetic conditions, it may be found as high as 0.5 per cent, or higher. This can be reduced by an insulin injection, but as soon as food rich in carbohydrate is eaten, back comes the sugar to a high level. In order to rest the pancreas, the blood sugar must be kept low, which can only be accomplished when the diet contains relatively little carbohydrate. THE DIET _Calories and sugar should be low._--All of the principal authorities on diabetes are agreed that a diabetic patient must not overeat and become fat. In other words, the total amount of food energy, that is, calories, must be limited. All are agreed also that the diet must be kept low in sugar producing foods. This means little carbohydrate and little protein. The diet in health, as I have said, includes a great deal of carbohydrate, probably more than is wise even for perfectly normal persons. The diet in diabetes must get more of its calories from fat and less from the starches and meats. Authorities are furthermore agreed that an excessive restriction of carbohydrate (sugar and starch) may be dangerous, because with such very low carbohydrate diets the fats may fail to be properly assimilated, with resulting acid poisoning. _The authorities agree on general principles._--The actual procedures in diet-planning employed by various authorities differ but little, and only as to details. Doctor Allen, for instance, believes in much greater restriction of total food than do others. Doctor Joslin also favors rather low total food amounts and disbelieves in allowing much fat unless rather large amounts of carbohydrate can be taken. Doctor Woodyat of Chicago, the doctors in the Toronto Clinic, and Doctor McCann at the University of Rochester, New York, plan their diets in such a way that approximately one part of carbohydrate will be taken for every two and one-half parts of fat. Professor Petren of Lund, Sweden, now the leading authority in Europe, and Doctor Newburgh and Doctor Marsh of the University of Michigan, believe that restricting protein is of extreme importance, and that if this is done acidosis can be avoided even when larger proportions of fat are fed. In the Mayo Clinic, the practice is to limit protein rigidly and to limit carbohydrate rather more strictly than is done elsewhere, making the diet consist to a greater extent of fat, but planning this so that the total energy of the daily food supply will meet quite closely actual energy requirements. The procedures for arriving at these several diets can be found in various manuals that have been written for patients.