Diabetics can consume whole wheat chapatis in moderation. When the whole wheat kernel is intact, the glycemic index is as low as 30. However, due to the process of milling, the glycemic index of wheat flour increases up to 70. Therefore, it may increase the postprandial (after meal) blood glucose levels enormously. Whole wheat has many vitamins, antioxidants, and dietary fiber, with its external layer intact. That is why diabetics can consume whole wheat. However, consult your doctor regarding the portion size according to your age, diabetes control, carbohydrate requirement, physical activity, and other health parameters.