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### Insulin Replacement & Dose Calculations - An Overview

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### Insulin Replacement & Dose Calculations - An Overview#5340

#5340
Basel and Bolus Insulin Replacement:

Approximately 40-50% of the total daily insulin dose is to replace insulin overnight, when you are fasting and between meals. This is called background or basal insulin replacement. The basal or background insulin dose usually is constant from day to day. The other 50-60% of the total daily insulin dose is for carbohydrate coverage (food) and high blood sugar correction. This is called the bolus insulin replacement.

Basal Insulin Dose Chart:

We’ll assume that your premeal blood sugar target is 120 mg/dL and that 1 unit will decrease your blood sugar by 50 points. If your blood sugar is below 60, do not administer insulin. Instead, you should immediately consume 15 grams of carbohydrates. Bolus Insulin Dose Chart:

We’ll assume that you take 1 unit of insulin is required for every 10 grams of carbohydrates. Total Daily Dose of insulin (TDD):

Total Daily Dose is the average of your daily basal and bolus insulin doses over a period of at least 14 days when using a pump. Your TDD is averaged for you by your pump. If you use an MDI (multiple daily injection), sum up all the doses of long- and short-acting insulin you take daily for one or two weeks, then divide the total by seven or fourteen.

The initial calculation of the basal/background and bolus doses requires estimating your total daily insulin dose:

Formulas Commonly Used to Create Insulin Dose Recommendations.

A. Total Daily Insulin Requirement

The general calculation for the body’s daily insulin requirement is:

• If you measure your body weight in pounds:
Total Daily Insulin Requirement (in units of insulin) = Weight in Pounds ÷ 4
• If you measure your body weight in kilograms:
Total Daily Insulin Requirement (in units of insulin) = 0.55 X Total Weight in Kilograms

B. The Carbohydrate Coverage Ratio:

Carbohydrate ratio is frequently set by the prescribers, but it should be revised on a regular basis (if needed). A carb ratio of 1:10 indicates that 1 unit of rapid-acting insulin covers 10 grams of carbohydrates. This can be calculated using the Rule of “500”: Carbohydrate Bolus Calculation.

"Rule of 500"

The 500 rule (also known as the 450 rule) is a popular strategy used by type 1 diabetes patients to predict how many carbs will be covered by one unit of fast-acting, or bolus, insulin. This is known as the insulin-to-carb ratio or, more colloquially, the carb factor.

500 ÷ Total Daily Insulin Dose= 1 unit insulin covers so many grams of carbohydrate.
Example:

If we assume a patient weights 160lbs means Total Daily Insulin dose (TDI) = 160 lbs. ÷ 4 = 40 units

Carbohydrate coverage ratio = 500 ÷ TDI (40 units) = 1unit insulin/ 12 g CHO

C. The High Blood Sugar Correction Factor:

A Correction Factor (also known as insulin sensitivity) is the amount of blood glucose that 1 unit of rapid acting insulin will drop in 2 to 4 hours while you are fasting or pre-meal. This can be calculated using the Rule of “1800”

"Rule of 1800"

For regular insulin, use the “1800 rule.” This tells you how much your blood sugar will drop for each unit of regular insulin.

Correction Factor = 1800 ÷Total Daily Insulin Dose = 1 unit of insulin will reduce the blood sugar so many mg/dl.
Example:

If we assume the patient's body weights 160lbs, Total Daily Insulin dose (TDI) = 160 lbs. ÷ 4 = 40 units
Correction Factor = 1800 ÷ TDI (40 units) = 1 unit insulin will drop, reduce the blood sugar level by 45 mg/dl

If the patient body weight weighed in kilogram = 57 kg means, Total Daily Insulin Requirement (in units of insulin) = 0.55 X Total Weight in Kilograms =0.55*57=31.35 units per day

D. Carbohydrates to Insulin Ratio

Bolus – Carbohydrate Coverage

It is prescribed as insulin to carbohydrate ratio. The insulin to carbohydrate ratio represents how many grams of carbohydrate are covered by 1 unit of insulin. (Generally, one unit of rapid-acting insulin will dispose of 12-15 grams of carbohydrate. This range can vary from 4-30 grams or more of carbohydrate, depending on an individual’s sensitivity to insulin.)

CHO insulin dose =Total grams of CHO in the meal ÷ grams of CHO disposed by 1 unit of insulin
Example:

Assume that,

• You are going to eat 60 grams of carbohydrate for lunch
• Your Insulin: CHO ratio is 1:10.
• CHO insulin dose = Total grams of CHO in the meal (60 g) ÷ grams of CHO disposed by 1 unit of insulin (10) = 6 units

Bolus – High Blood Sugar Correction/ Insulin Sensitivity Factor

It is defined as how much one unit of rapid-acting insulin will drop the blood sugar. Generally, 1 unit of insulin is needed to drop the blood glucose by 50 mg/dl, and it depends on individual insulin sensitivities.

High blood sugar correction dose = Difference between actual blood sugar and target blood sugar÷ correction factor.
Example:

Assume that,

• 1 unit will drop your blood sugar 50 points (mg/dl) and the high blood sugar correction factor is 50
• Pre-meal blood sugar target is 120 mg/dl.
• Your actual blood sugar before lunch is 220 mg/dl.

Now, calculate the difference between your actual blood sugar and target blood sugar: 220 minus 120 mg/dl = 100 mg/dl

Correction dose = Difference between actual and target blood glucose (100 mg/dl) ÷ correction factor (50) = 2 units of rapid acting insulin.
So, you will need an additional 2 units of rapid acting insulin to “correct” the blood sugar down to a target of 120 mg/dl.

Total Mealtime Dose

To get the total mealtime insulin dose, add the CHO insulin dose together with the high blood sugar correction insulin dose:

Total Mealtime Dose=CHO Insulin Dose + High Blood Sugar Correction Dose = Total Meal Insulin Dose
Example:

Assume that,

• The carbohydrate coverage dose is 6 units of rapid acting insulin.
• The high blood sugar correction dose is 2 units of rapid acting insulin. Now, add the two doses together to calculate your total meal dose.
• Carbohydrate coverage dose (6 units) + high sugar correction dose (2 units) = 8 units total meal dose.
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