Endocrinology Book

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Carbohydrate Count in Insulin DosingAka: Insulin Adjustment with Carbohydrate Counting

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  1. See Also
    1. Carbohydrate Counting
    2. Insulin Dosing
    3. See Insulin Dosing in Type I Diabetes
    4. See Insulin Dosing in Type II Diabetes
  2. Step 1a: Determine Carbohydrate to Insulin ratio
    1. Determine total Insulin used per day
      1. Assumes multiple daily doses or Insulin pump
      2. Otherwise use simple method below in Step Ib
    2. Calculate carbohydrate to Insulin ratio
      1. Short-acting rapid Insulin: Humalog (Lispro)
        1. Ratio = 500 / (total daily Insulin dose)
      2. Short-acting Insulin: Regular
        1. Ratio = 450 / (total daily Insulin dose)
    3. Interpretation
      1. Ratio is carbohydrate grams covered by 1 unit Insulin
      2. Type I Diabetes
        1. One unit per carbohydrate (15 grams) is typical
        2. Effect of one unit Insulin on glucose lowering
          1. One Unit bolus Insulin lowers glucose 20-60 mg/dl
          2. Estimate: 1800/(daily Insulin dose)
    4. Example
      1. Patient uses 35 total units of Lispro per day
      2. One unit Insulin covers 500/35 or 14 g carbohydrates
  3. Step 1b: Alternative to Step 1a (Simple Method)
    1. Dietician directs grams of carbohydrate per meal
      1. Estimate Daily Energy Allowance (calories)
      2. Estimate percentage of calories in diet (50-60%)
      3. Calories per gram of carbohydrate = 4
      4. Calculate total daily carbohydrate grams
        1. Daily Carbs (grams) = (Total Calories x 0.5) / 4
        2. Example = (1800 x 0.5)/4 = 225 carbohydrate grams
      5. Spread out carbohydrate grams across meals
        1. Example: 70 grams per meal, and two 20 gram snacks
    2. Choose carbohydrate servings to meet needs
      1. Each serving contains 12-15 grams carbohydrate
      2. Choose servings from 3 groups
        1. Breads and starches
        2. Fruit
        3. Milk
        4. Vegetables are not counted
  4. Step 2: Predict carbohydrate effect on Serum Glucose
    1. Glucose rises at constant rate per gram carbohydrate
      1. Weight 100 lbs: 1g carb raises glucose 5 points
      2. Weight 150 lbs: 1g carb raises glucose 4 points
      3. Weight 200 lbs: 1g carb raises glucose 3 points
    2. Other modifiers of carbohydrate effect on Serum Glucose
      1. Glycemic Index
      2. Percentage of food from protein and fat
  5. Step 3: Count Carbohydrates
    1. Indications
      1. Estimate Insulin needs per meal
      2. Plan meal to raise glucose to certain level
    2. Techniques
      1. Food labels (use grams of carbohydrate per serving)
      2. Food tables (e.g. cookbooks, references)
      3. Food weight
        1. Determine Carb Factor for particular food
          1. Percentage of given food from carbohydrate
        2. Weigh food on gram scale
        3. Carbohydrate grams = (food weight) x (carb factor)

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