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Well, the correct answer is that a person with diabetes really is not restricted to eating certain foods, so while a candy bar may not be the best choice nutritionally, an occasional indulgence is understandable. A candy bar usually has about 220-250 calories and somewhere between 25-30 grams of carbohydrates. On average, most patients with diabetes require one unit of insulin for every 10-15 grams of carbohydrates they eat. So you could try two units of a short acting insulin and see how you do. However, it is really important that you meet with a diabetes educator/nutritionist to see what your insulin ratios are, and what your sensitivity is. You should not consider insulin an option to "knock out" the sugar in the candy bar. It is more complicated than that. The type of carbohydrate, what it is combined with, and what your glucose level is before you start eating are all factors to be considered. I would strongly suggest you meet with a diabetes educator/nutritionist or your physician before you move ahead and adjust any insulin doses by yourself.
Medically reviewed by John A. Daller, MD; American Board of Surgery with subspecialty certification in surgical critical care
"Nutritional considerations in type 2 diabetes mellitus"