Black beans have a glycemic index of 42. Glycemic index reflects the ability of a food to affect blood glucose. Foods are generally categorized into three levels according to their glycemic index: low glycemic index foods, which have a glycemic index of less than 55; medium glycemic index foods, which have a glycemic index of 55-70; and high glycemic index foods, which have a glycemic index of 70 or more. Since black beans have a glycemic index of 42, they are a low glycemic index food. Low glycemic index food, for diabetic patients is appropriate to eat more. Moreover, black beans also contain some dietary fiber, which helps to enhance the sense of satiety, so black beans are a relatively good food for diabetics. You can consult a professional nutritionist to develop an individualized diet plan.