Since in this approach, the carbohydrate ratio is only used to account for non-standard carbohydrate intakes, it is usually not required to work with meal specific ratios.
The result is that the blood glucose level rises somewhat after eating, and within an hour or so, returns to the normal fasting level. Even the best diabetic treatment with synthetic human insulin or even insulin analogs, however administered, falls far short of normal glucose control in the non-diabetic.Complicating matters is that the composition of the food eaten (see glycemic index) affects intestinal absorption rates. Glucose from some foods is absorbed more (or less) rapidly than the same amount of glucose in other foods. In addition, fats and proteins cause delays in absorption of glucose from carbohydrates eaten at the same time. As well, exercise reduces the need for insulin even when all other factors remain the same, since working muscle has some ability to take up glucose without the help of insulin.Because of the complex and interacting factors, it is, in principle, impossible to know for certain how much insulin (and which type) is needed to cover a particular meal to achieve a reasonable blood glucose level within an hour or two after eating. Non-diabetics beta cells routinely and automatically manage this by continual glucose level monitoring and insulin release. All such decisions by a diabetic must be based on experience and training (i.e., at the direction of a physician, PA, or in some places a specialist diabetic educator) and, further, specifically based on the individual experience of the person. But it is not straightforward and should never be done by habit or routine.