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Carbohydrate Count in Insulin Dosing
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Carbohydrate Count in Insulin Dosing
, Insulin Adjustment with Carbohydrate Counting
See Also
Carbohydrate Counting
Insulin Dosing
See
Insulin Dosing in Type I Diabetes
See
Insulin Dosing in Type II Diabetes
Management
Step 1a - Determine Carbohydrate to
Insulin
ratio
Determine total
Insulin
used per day
Option 1: Known dose from multiple daily doses or
Insulin Pump
Option 2: Calculate based on patient weight
Type I: Total daily
Insulin
(TDI)
TDI = WtKg x 0.1 to 0.3 units/kg (start low)
Type I: Total basal dose (TBD)
TBD = WtKg x 0.2
TBD = 0.4 x Total Daily
Insulin
(TDI)
Type II: Total daily
Insulin
(TDI)
TDI = WtKg x 0.3 units/kg: Underweight, advance age,
Dialysis
TDI = WtKg x 0.4 units/kg: Normal weight
TDI = WtKg x 0.5 units/kg:
Overweight
TDI = WtKg x 0.6 units/kg: Obese, steroid use, high
Insulin Resistance
Option 3: Simple carbohydrate based-method (below in Step Ib)
Plan to split the basal
Insulin
and
Bolus Insulin
evenly (50% to each)
Calculate
Insulin
to carbohydrate ratio or ICR (g carb per one unit
Insulin
)
Short-acting rapid
Insulin
:
Humalog
(
Lispro
)
Ratio (ICR) = 500 / (total daily
Insulin
or TDI dose)
Short-Acting Insulin
: Regular
Ratio (ICR) = 450 / (total daily
Insulin
dose)
Other formulas
Ratio (ICR) = 100 / (total basal dose or TBD)
Calculate correction factor (CF)
Blood Glucose
drop expected per unit of
Insulin
(using the
Insulin
-carb ratio or ICR above)
Formula
CF = ICR * 4.5
For example
Given
Insulin
to carbohydrate ratio of 6 g carb/unit
Blood Glucose
would correct 27 mg/dl with one unit
Insulin
Interpretation
Ratio is carbohydrate grams covered by 1 unit
Insulin
Type I Diabetes
One unit per carbohydrate (15 grams) is typical
Effect of one unit
Insulin
on
Glucose
lowering
Typically 1 Unit
Bolus Insulin
lowers
Glucose
20-60 mg/dl
Estimate: 1800/(daily
Insulin
dose)
Example
Type I Diabetes
patient weighs 110 kg and uses ~35 total units of
Insulin
per day (0.3 units/kg)
One unit
Insulin
covers 500/35 or 14 g carbohydrates
One unit
Insulin
would be expected to lower
Glucose
1800/35 or 50 mg/dl (in
Type I Diabetes Mellitus
)
Lantus
: Takes 18 units of
Lantus
per day
Lispro
: Takes 16 units total (4 units for each of 3 meals and 2 units for each of 2 snacks)
Management
Step 1b - Alternative to Step 1a (Simple Method)
Dietician directs grams of carbohydrate per meal
Estimate
Daily Energy Allowance
(calories)
Estimate percentage of calories in diet (50-60%)
Calories per gram of carbohydrate = 4
Calculate total daily carbohydrate grams
Daily Carbs (grams) = (Total Calories x 0.5) / 4
Example = (1800 x 0.5)/4 = 225 carbohydrate grams
Spread out carbohydrate grams across meals
Example: 70 grams per meal, and two 20 gram snacks
Choose carbohydrate servings to meet needs
Each serving contains 12-15 grams carbohydrate
Choose servings from 3 groups
Breads and starches
Fruit
Milk
Vegetables are not counted
Management
Step 2 - Predict carbohydrate effect on
Serum Glucose
Glucose
rises at constant rate per gram carbohydrate
Weight 100 lbs: 1g carb raises
Glucose
5 points
Weight 150 lbs: 1g carb raises
Glucose
4 points
Weight 200 lbs: 1g carb raises
Glucose
3 points
Other modifiers of carbohydrate effect on
Serum Glucose
Glycemic Index
Percentage of food from protein and fat
Management
Step 3 - Count Carbohydrates
Indications
Estimate
Insulin
needs per meal
Plan meal to raise
Glucose
to certain level
Techniques
Food labels (use grams of carbohydrate per serving)
Food tables (e.g. cookbooks, references)
Food weight
Determine Carb Factor for particular food
Percentage of given food from carbohydrate
Weigh food on gram scale
Carbohydrate grams = (food weight) x (carb factor)
Management
Step 5 - Summary: Combining
Insulin
protocols
Basal
Insulin
(Maintenance, covers between meals and ovenight)
Once daily:
Lantus
Twice daily:
Levemir
,
NPH Insulin
Bolus Insulin
(pre-meal
Insulin
, covers post-meal
Blood Sugar
s)
Units per carbohydrate of planned meal AND
Units of
Correctional Insulin Dosing
based on
Blood Sugar
s over 149 before the meal
Example
A 70 kg man with
Type II Diabetes Mellitus
Insulin Glargine
(
Lantus
)
Uses 14 units per day at dinner
Insulin
Humalog
(
Lispro
) with coverage
Uses 1 unit per carbohydrate PLUS 1 unit per 50 over 150
Blood Sugar
of 200 at lunch and having prepared a 4 carbohydrate meal
Takes a total of 6 units: 4 units (4 carbs) plus an additional 2 units (for
Blood Sugar
of 200)
References
Smith (2018) Am Fam Physician 98(3): 154-62 [PubMed]
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