200 seems to be the magic number for most adults. 180 to 220 is in a range that's good. You must have some sugar in the blood or you will go into insulin shock. Too much sugar and you go into a diabetic coma. Too much would be 400 - 500 - 600 etc. Above that and you are in "serious" trouble. Too little would be 30 - 40 - 50. Your blood sugar does not remain the same at all times. After you eat, depending on what you eat, your blood sugar will rise. If you fast for a long period of time, your blood sugar will drop. Healthy people will have their pancreas kick in and drop the sugar level, or they will take body fat, convert it to carbohydrates and elevate their blood sugar.