There is nothing much to do if you are diabetic. Are you using insulin or are you using tablets? I know diabetic patients who are taking only tablets and they are fasting every year without any trouble. You should be careful not to have low blood sugar due to fasting. Take easily digestable carbohydrate food at iftar time and take the other type for suhur. Monitor your blood sugar level regularly and keep always some candies with you. You should control intake of high calorie food for iftar and for suhur as it will increase your blood sugar.