Your doctor will prescribe an insulin dosing regimen for you to get you started on your type 1 diabetes that will include the three components of intensive insulin therapy:
- Basal Insulin Dosage – a once or twice daily dose of long acting insulin [glargine or detemir]
- Bolus Dosage – a short acting insulin dosage based on the amount of the carbohydrates in each meal [aspart, glulisine, or lispro] (To learn how to determine the amount of carbohydrates in each meal see Counting Carbohydrates from Diabetes Education Online).
- Bolus Correction Dose For A High Blood Sugar – a correction factor dosage to bring your blood sugar level back to the target range when it gets too high (out of the target range) [aspart, glulisine, or lispro].
However, each of these three dosages can change over time or even throughout the day and you will learn how to adjust up or down each of these three components.
Of course, your diabetes team should always be available by phone or internet to counsel you on an appropriate insulin dosage for any of the three components of intensive insulin therapy if you’re unsure.
*Example #4, “Formulas commonly used to create insulin dose recommendations” is in the next post of my blog study notes (and, of course, on the “Calculating Insulin Dosage” page from Diabetes Education Online).
First, some basic things to know about insulin:
- 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.
Bolus – Carbohydrate coverage
The bolus dose for food coverage is prescribed as an insulin to carbohydrate ratio. The insulin to carbohydrate ratio represents how many grams of carbohydrate are covered or disposed of 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 6-30 grams or more of carbohydrate depending on an individual’s sensitivity to insulin. Insulin sensitivity can vary according to the time of day, from person to person, and is affected by physical activity and stress.
Bolus – High blood sugar correction
(also known as insulin sensitivity factor)
The bolus dose for high blood sugar correction is defined as how much one unit of rapid-acting insulin will drop the blood sugar.
Generally, to correct a high blood sugar, one unit of insulin is needed to drop the blood glucose by 50 mg/dl. This drop in blood sugar can range from 30-100 mg/dl or more, depending on individual insulin sensitivities, and other circumstances.
Read some examples and therapeutic principles on how to calculate the carbohydrate coverage dose, high blood sugar correction dose and the total mealtime insulin dose.
Example #1: Carbohydrate coverage at a meal
First, you have to calculate the carbohydrate coverage insulin dose using this formula:
CHO insulin dose =
Total grams of CHO in the meal
÷ grams of CHO disposed by 1 unit of insulin
(the grams of CHO disposed of by 1 unit of insulin is the bottom number or denominator of the Insulin:CHO ratio).
For Example #1, assume:
- You are going to eat 60 grams of carbohydrate for lunch
- Your Insulin: CHO ratio is 1:10
To get the CHO insulin dose, plug the numbers into the formula:
CHO insulin dose =
Total grams of CHO in the meal (60 g)
÷ grams of CHO disposed by 1 unit of insulin (10) = 6 units
You will need 6 units of rapid acting insulin to cover the carbohydrate.
Example #2: High blood sugar correction dose
Next, you have to calculate the high blood sugar correction dose.
High blood sugar correction dose =
Difference between actual blood sugar and target blood sugar*
÷ correction factor.
*Actual blood sugar minus target blood sugar
For Example #2, assume:
- 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
To get the high blood sugar correction insulin dose, plug the numbers into this formula:
Correction dose =
Difference between actual and target blood glucose (100mg/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.
Example #3: Total mealtime dose
Finally, to get the total mealtime insulin dose, add the CHO insulin dose together with the high blood sugar correction insulin dose:
CHO Insulin Dose
+ High Blood Sugar Correction Dose
= Total Meal Insulin Dose
For Example #3, assume:
- 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!
The total lunch insulin dose is 8 units of rapid acting insulin.
Example #4, “Formulas commonly used to create insulin dose recommendations” is in the next post of my blog study notes (and, of course, on the “Calculating Insulin Dosage” page from Diabetes Education Online).