Foods and Their Effect on Blood Sugar
( for the insulin user ) Part 1 of 2


Since food is one of the many things that can change your blood sugar, it is possible to use it to manage your diabetes. Using food to manage your diabetes does not mean that you must follow a rigid diet or always eat the same food. But, it does mean that you need to learn how changes in your food intake affect your blood sugar. Once you learn this, you will be able to eat a wide variety of foods without worrying that your blood sugar will go too high or too low.

Learning how to vary your food choices and how to eat more or less of a food is a lot of work. First, you must study how food affects your blood sugar under one set of conditions. Only then can you study and learn how to eat under other conditions.

Remember that food is not the only thing that can change your blood sugar. If your insulin prescription is not adjusted correctly, your blood sugar response may not be predictable. Insulin type, amount and site of injection can alter the blood sugar response. Activity and stress can also change your responses.


These guidelines will help you to learn how food effects your blood sugar.

I. Learn the carbohydrate (CHO) content of foods you eat

Carbohydrates are the only nutrients that turn completely into glucose. They are vital because of the energy they provide to your body. They cannot be eliminated. In fact, a diet that is too low in carbohydrates can trigger a process that increases your blood sugars.

Don't worry about the other nutrients, proteins and fats, for now. Fats do not turn to glucose, and proteins only have a minimal effect which is spread out over several hours. Their conversion to sugar is so delayed and so gradual that regulating protein intake is hardly ever necessary. HOWEVER, proteins and fats are important to consider if you are watching your weight. They both contain a lot of calories. While they probably won't raise your blood sugar, they are sure to raise your weight!

A. To discover the CHO content of foods, you can:

1) Check food labels

2) Purchase an inexpensive carbohydrate counter (Calories & Carbohydrates by Barbara Kraus is a good one)

3) Use the diabetic exchange list (Each group specifies the amount of carbohydrate, protein, fat and calories that is contained within its foods.)

4) Surf the internet. is a good one
II. Learn the differences among CHO

There are two kinds of carbohydrates -- simple and complex. Simple carbohydrates are converted to glucose in 5-30 minutes. They include:
regular soda
fruit juices
Complex carbohydrates are converted to glucose more slowly, usually in 30-90 minutes. They include:

Because simple carbohydrates turn to sugar so quickly, it is more difficult to match them with injected insulin. The slower conversion of complex carbohydrates, on the other hand, can be more easily matched to the activity of injected insulin.

The fiber content of the carbohydrate can also alter the food's change to glucose. The more fiber in a food, the slower the conversion of that food to glucose. Some high fiber foods might cause the blood sugar to raise less quickly than foods that are low in fiber.
III. Establish guidelines

Carbohydrates (CHO) are necessary for the energy they provide to the body. A person needs at least 100-125 gm. CHO everyday. Depending on your calorie needs, you may need more than 100 gm. but never less! By keeping the CHO constant from meal to meal, you can discover how that "meal" fits with your insulin, activity, etc. Remember, this is an experiment -- not a lifelong diet. You must learn the impact of one "package" of food before you will be able to predict the effect of others. Meet with your diabetes team or with a nutritionist to learn more about carbohydrates.

A. Divide the days total CHO into at least three meals (and three snacks depending on your insulin prescription)

1) Schedule the meals/snacks to match your insulin prescription:

Injected insulin works on its own time schedule. To get the most from it, you need to match your food intake to its activity. Because most insulins work longer than "real thing," you almost always need snacks if your plan includes Regular insulin pre meal or large doses of intermediate acting insulin.

If you take this insulin then
You should eat a meal or snack in:
rapid-acting (Humalog)
5 minutes
short-acting (Reg, Actrapid, Velosulin)
1/2 hr
2 1/2 hrs
medium-acting (NPH, Lente)*
4-5 1/2 hrs
7-8 hrs
short & medium-acting
(Reg & NPH,Lente)
1/2 hr
4-5 1/2 hrs
2 1/2 hrs
7-8 hrs
rapid & medium-acting
(Humalog & NPH, Lente)
5 minutes
4-5 1/2 hrs
2 1/2 hrs
7-8 hrs
long-acting (UL)
* If Lente or NPH is taken in doses less than 3 to 6 units, it does not require a specific meal time.

2) Limit CHO at breakfast and mid-morning.

The body is often resistant to insulin in the morning. There are hormones secreted before awakening which "weaken" the insulin. More insulin is needed to match a meal eaten at breakfast than if the same meal was eaten at lunch or supper. A good rule of thumb is to start with a CHO amount that is no more than 20% of the days total amount.
B. Limit yourself to complex CHO

Because simple sugars raise the blood sugar quickly, it is more difficult to match them to injected insulin. Consider avoiding all simple CHO while you are experimenting. They make it more difficult to "make sense" of the experiment. (You should still use these foods to correct severely lowered blood sugar or before/during/after exercise if they are needed.) Once you have mastered the more basic foods, then you'll have the chance to add back some or all of the foods you are now avoiding.

Unfortunately, fruit juices and most fruits contain a lot of sugar. Their impact on the blood sugar is little different than the impact of table sugar. Milk and yogurt also contain some sugar and may cause your blood sugar to raise too quickly or too high especially if taken in the morning. You may also need to use these foods sparingly during the stabilization phase.
C. Increase the number of blood tests

By checking your blood sugar about before the meal (5minutes if Humalog and 1/2 hour if Regular) and one hour after the meal, you can determine the impact of the carbohydrate on your blood sugar.

1) If the blood sugar level changed by more than 40-50 mg (either increasing or decreasing) then that "package" of food, insulin and/or activity did not match. Something will need changing — either the amount of timing of the insulin, the amount or type of carbohydrate or the frequency or intensity of the activity.

Carolyn Robertson, RN, MSN, CS, CDE

Don't Miss part II next month!

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