Proper control of blood sugar requires measurement. There are two ways to do this. You can apply a drop of blood to a detector and determine the sugar concentration at that instant (blood sugar fluctuates up and down with diet, exercise, stress, and poorly understood factors). This allows you to calculate the dose of insulin to be injected in order to keep the blood sugar from rising too high or falling too low. Another measure of blood sugar makes use of the level of hemoglobin A1c in red blood cells. Hemoglobin A1c is hemoglobin with a glucose molecule attached, the natural result of blood cells floating in a sugar-containing soup. The higher the average blood sugar level, the higher the hemoglobin A1c concentration will be, making it a good tool to ascertain blood sugar control in general. If you don't have diabetes, typically a sugar molecule will be attached to between 4 percent and 6 percent of your blood's hemoglobin. In the United States, doctors consider diabetes to be well controlled if the hemoglobin A1c level is 7 percent or so; in Europe a tighter level of control is typically targeted—maybe around 6.5 percent. The higher the average blood sugar (measured as hemoglobin A1c), the greater the risk of complications.