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


Getting the right "package" may take some work. But, this is where we can help you the most! Remember that you don't need to study the whole day at once. You can select one meal at a time for study.

A. Certain factors will change how you respond to even the same meal.
  1. Timing

    If you take insulin injections, it works on its own program. It must be taken before it is needed and the person must adjust the diet and activity to match the insulin's behavior. Eating before the "right" time means there will not be enough insulin to match the rise in sugar from the meal and the blood sugar will raise too high. Eating a meal or snack later than the "right" time means the insulin will probably cause the blood sugar to lower too much because the anticipated food was not eaten.

  2. Exercise

    Exercise before a meal can change your insulin needs. Often the body must replace the energy used during aerobic exercise. As a result, some people need less insulin for as little as two hours and as long as 24 hours after exercise.

  3. Stress

    Stress can both raise and lower your blood sugar. Since it is not easy to control your stress level, keep a record which notes your stress. This includes emotional stress, physical stress (cold, viruses & infections) and body stress (menstruation.)

  4. Hypoglycemia or Widely Swinging Blood Sugar Levels

    Your body has the ability to "correct" low blood sugars. Before you developed diabetes, the system was extremely effective in regulating the sugar level of the blood. It could raise the sugar when it was getting too low and lower the sugar when it was getting too high.

    The diabetes upset the system's ability to lower the sugar, but the system is still able to raise the sugar. Anytime the sugar drops quickly, drops more than 70-120 mg or goes low, the system will try to reverse the trend. This causes the blood sugar to rise without eating. It can affect the blood sugar levels as late as 24 hours after the initial episode!!!

  5. Injection Technique

    Some areas that can be used for injection absorb insulin more quickly than others. Also areas that have been used a lot or areas that are thickened or numb will prevent the insulin from working well. How deeply the insulin is injected also affects the workings of the insulin. Avoid injecting in a different zone with each injection. Instead, rotate sites within a particular zone.

  6. Unpredictable Foods

    Carbohydrates will not always affect the blood sugar in the same way. How long the carbohydrate is cooked (the longer cooked, the more "sugars" released), how it is prepared (cutting, mashing, stewing destroys fibers and make it more digestible), and when it is eaten will all change the foods' effect on your blood sugar.

    There are many foods that may or may or may not contain simple carbohydrates. The manufacturer, the restaurant or the cook might add sugar or a sugar-like substance to the food to improve its appearance, its smell or its taste. This hidden sugar could change your blood sugar dramatically.

    Foods which might have an unpredictable effect (either they are coated with sugar or a sugar like substance or they consist of a sugar like substance that is used to help with browning or for flavor) are:

    • pizza
    • bagels
    • salad dressing
    • "shiny" french fries or onion rings
    • tomato sauce or tomato based products
    • peanut butter
    • soy sauce
    • italian food
    • chinese/japanese food

B. Use a diary to keep track of all the information

Almost any record which lists the blood sugar levels, the insulin, the food, the activity and stress will do. Records give you the chance to study what is happening and provide the clues that you need to decide the changes that might be needed.

C. Decide if the insulin/food package fits

A normal blood sugar may be your goal, but depending on your starting blood sugar, it might be necessary to make change slowly. Blood sugar levels that are lowered too quickly will not remain low. The system will "fight" the change and quickly raise it again. This can occur even when the sugar does not go low.

Here are some guidelines you can use to judge the insulin "fit". You should check with your diabetes team to review these targets ( it is likely that the specific ranges may need to be altered to match your particular needs)


1. If pre- meal insulin is Humalog and :

If pre meal blood sugar is
Then 1hour post should be: & next premeal should be:
<100 mg/dl 120 to 160mg/dl 100 to 120mg/dl
100-150 mg/dl 20 to 40 mg/dl higher The same as the premeal
151-200 mg/dl 0 to 20mg/dl higher 0 to 20mg less than the premeal
201-250mg/dl 0 to 20mg/dl lower 20 to 40mg less than the premeal
251-300mg/dl 20 to 40mg/dl lower 40 to 60mg less than the premeal
>300mg/dl 40 to 60mg/dl lower 60 to 80mg less than the premeal

If pre meal insulin is Regular and:

If pre meal blood sugar is
Then 1hour post should be: & next premeal should be:
<100 mg/dl 140 to 180mg/dl 120 to 140mg/dl
100-150 mg/dl 40 to 60 mg/dl higher The same as the premeal
151-200 mg/dl 20 to 40mg/dl higher 0 to 20mg less than the premeal
201-250mg/dl 0 to 20mg/dl higher 20 to 40mg less than the premeal
251-300mg/dl 0 to 20mg/dl lower 40 to 60mg less than the premeal
>300mg/dl 20 to 40mg/dl lower 60 to 80mg less than the premeal

D. Look for trends

Injected insulin is not as good as the real thing. There will be times when the blood sugar will increase or decrease without any clear reason. It is important to study your blood sugar and only make changes based on several unwanted blood sugars rather than a single "bad" number. Here are a few of the more common patterns and some of their causes. Don't worry if this looks confusing. We will help you to understand. With time and practice, it will begin to make sense.

  1. Blood sugar always high after meals

    Possible explanations - insulin dose is too low, meal eaten too soon after the shot, CHO amount too large for the insulin, possiblity of hidden sugar, look for rebound.

  2. Blood sugar always low before one or more meals

    Possible explanations - insulin dose too large, excessive overlap of insulins, meal or snack eaten too late, snack skipped , CHO amount too small for the insulin, prolonged effect from exercise, alcohol ingestion.

  3. Blood sugar in morning higher than bedtime

    Possible explanations - evening insulin too low in dose or taken too early, bedtime snack too large or with too much simple CHO or evening insulin too high in dose or taken too late, bedtime snack too small, low blood sugar during the night causing rebound.

  4. Blood sugar after breakfast high and hard to lower

    Possible explanations - CHO intake too large, breakfast contains simple CHO, low blood sugar during the night causing rebound.

E. Make change slowly

Your body gets accustomed to a certain blood sugar range. if the blood sugar has been high, lowering it too quickly we assure that it will again get high. Also, changes often take a few days to "become effective". The true effect of any dose change will not be seen for two to four days.


Must be guided by blood sugar determinations and review of records that note food intake, activity, medications and stress. Daily insulin adjustment should be avoided.

These are some tentative guidelines for adjustment of an intensive insulin regime: Consider each of the following if blood sugar is too high on three consecutive days,

  1. before breakfast:

    • increase evening dose of NPH or Lente
    • modify amount/type of bedtime snack
    • move evening dose to pre supper

  2. before lunch:

    • increase morning dose of Regular/Humalog
    • decrease amount of breakfast
    • modify timing/amount of AM snack

  3. before supper:

    • increase morning dose of NPH or Lente
    • modify amount/type of lunch
    • modify amount/type of afternoon snack

  4. before bed:

    • increase evening dose of Regular/Humalog
    • modify amount/timing of supper
    • modify amount/type of evening snack

Carolyn Robertson, RN, MSN, CS, CDE

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