“Formulas Commonly Used To Create Insulin Dose Recommendations” In Type 1 Diabetes From Diabetes Education Online

The first three examples of calculating insulin dosages for Type 1 diabetes from “Calculating Insulin Dosage” are in a previous post on my blog study notes (and, of course on the Calculating Insulin Dosage page of Diabetes Education Online).

Remember from the above that 40 – 50% of your total daily insulin replacement therapy will be basal (long – acting) insulin given once or twice daily to cover your body’s insulin requirements between meals, when you are fasting, and overnight.

The rest of your total daily insulin requirement (50 – 60% of daily requirement) will be divided into two components (and calculated seperately):

1. Bolus for Carbohydrate Coverage [for food eaten] – Prescribed as Insulin To Carbohydrate Ratio (See Counting Carbohydrates from Diabetes Education Online)
   1. “The insulin to carbohydrate ratio represents how many grams of carbohydrate are covered or disposed of by 1 unit of insulin.”
   2. “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.”
   3. “Insulin sensitivity can vary according to the time of day, from person to person, and is affected by physical activity and stress.”
2. Bolus for High Blood Sugar Correction – Prescribed as the Insulin Sensitivity Ratio
   1. “The bolus dose for high blood sugar correction is defined as how much one unit of rapid-acting insulin will drop the blood sugar.”
   2. “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.”

In Example #4 below we’ll learn how to calculate a total daily insulin dosage and then we’ll go through examples to work out

1. the dose of basal (long acting) insulin,
2. the bolus dose for the carbohydrates in a meal (determined by carbohydrate counting),
3. and the bolus dose for high blood sugar correction (Insulin Sensitivity Ratio)

What follows is “Example #4, Formulas commonly used to create insulin dose recommendations,” from Calculating Insulin Dosage page of Diabetes Education Online:

Example #4: Formulas commonly used to create insulin dose recommendations

This example illustrates a method for calculating of your background/basal and bolus doses and estimated daily insulin dose when you need full insulin replacement. Bear in mind, this may be too much insulin if you are newly diagnosed or still making a lot of insulin on your own. And it may be too little if you are very resistant to the action of insulin. Talk to your provider about the best insulin dose for you as this is a general formula and may not meet your individual needs.

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

Total Daily Insulin Requirement:

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

 Total Daily Insulin Requirement (in units of insulin)
= Weight in Pounds ÷ 4

Alternatively, if you measure your body weight in kilograms:

Total Daily Insulin Requirement (in units of insulin)
= 0.55 X Total Weight in Kilograms

Example 1:

If you are measuring your body weight in pounds:

• Assume you weigh 160 lbs.

In this example:

TOTAL DAILY INSULIN DOSE
= 160 lb ÷ 4 = 40 units of insulin/day

Example 2:

If you are measuring your body weight in kilograms:

• Assume your weight is 70Kg

In this example:

TOTAL DAILY INSULIN DOSE
= 0.55 x 70 Kg = 38.5 units of insulin/day

If your body is very resistant to insulin, you may require a higher dose. If your body is sensitive to insulin, you may require a lower insulin dose.

Basal/Background and Bolus Insulin Doses

Next, you need to establish the basal/background dose,  carbohydrate coverage dose (insulin to carbohydrate ratio) and high blood sugar correction dose (correction factor).

Basal/background insulin dose:

Basal/background Insulin Dose
= 40-50% of Total Daily Insulin Dose

Example:

1. Assume you weigh 160 pounds
2. Your total daily insulin dose (TDI) = 160 ÷ 4 = 40 units.

In this example:

Basal/background insulin dose
= 50% of TDI (40 units) = 20 units
of either long acting insulin, (such as glargine or detemir) or rapid acting insulin if you are using an insulin pump (continuous subcutaneous insulin infusion device).

The carbohydate coverage ratio:

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

This can be calculated using the Rule of “500”: Carbohydrate Bolus Calculation

In this example :

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

This example above assumes that you have a constant response to insulin throughout the day. In reality, individual insulin sensitivity varies. Someone who is resistant in the morning, but sensitive at mid-day, will need to adjust the insulin-to-carbohydrate ratio at different meal times. In such a case, the background insulin dose would still be approximately 20 units; however, the breakfast insulin-to-carbohydrate ratio might be breakfast 1:8 grams, lunch 1:15 grams and dinner 1:12 grams.

The high blood sugar correction factor:

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

This can be calculated using the Rule of “1800”.

Example:

1. Assume your total daily insulin dose (TDI) = 160 lbs ÷ 4 = 40 units

In this example:

Correction Factor
= 1800 ÷ TDI (40 units)
= 1 unit insulin will drop reduce the blood sugar level by 45 mg/dl

While the calculation is 1 unit will drop the blood sugar 45 mg/dl, to make it easier most people will round up or round down the number so the suggested correction factor may be 1 unit of rapid acting insulin will drop the blood sugar 40-50 mg/dl.

Please keep in mind, the estimated insulin regimen is an initial “best guess” and the dose may need to be modified to keep your blood sugar on target.

Also, there are many variations of insulin therapy. You will need to work out your specific insulin requirements and dose regimen with your medical provider and diabetes team.