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About

Effective diabetes management relies on mimicking the body's natural insulin response. For individuals on Multiple Daily Injections (MDI) or pump therapy, calculating the precise bolus is a meal-time necessity. This calculator integrates two critical components: the "Carbohydrate Coverage" (food dose) and the "Correction Dose" (to lower pre-meal hyperglycemia).

The calculation depends on user-specific constants: the Insulin-to-Carbohydrate Ratio (ICR) and the Insulin Sensitivity Factor (ISF). Errors in these calculations can lead to hypoglycemia (insulin shock) or persistent hyperglycemia (ketoacidosis risk). This tool standardizes the math, allowing for quick adjustments based on current Blood Glucose (BG) readings and planned carbohydrate intake.

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Formulas

The Total Bolus is the sum of the Correction Dose and the Carb Dose. Negative correction results (when BG is below target) may be subtracted from the carb dose depending on the plan.

Bolustotal = BGcurrent BGtargetISF + CarbsICR

Where ISF is the Sensitivity Factor and ICR is the Insulin-to-Carb Ratio.

Reference Data

MetricUnitDescriptionTypical Formula (Rule of 1800/500)
ISFmg/dL/UDrop in BG per 1 Unit Insulin1800 ÷ TDD
ISF (SI)mmol/L/UDrop in BG per 1 Unit Insulin100 ÷ TDD
ICRg/UGrams of Carbs covered by 1 Unit500 ÷ TDD
Targetmg/dLDesired Blood Glucose LevelUsually 100 - 120

Frequently Asked Questions

The Rule of 1800 is an estimation method used to find a starting Insulin Sensitivity Factor (ISF) for rapid-acting insulin. It calculates ISF as 1800 divided by the Total Daily Dose (TDD) of insulin. For example, if TDD is 60 units, ISF is approx 30 mg/dL/unit.
This logic is primarily designed for Rapid-Acting Analogues (Humalog, Novolog, Apidra). Regular insulin has a different onset and peak profile. The "Rule of 1500" is typically used for Regular insulin instead of 1800, affecting the ISF calculation.
If the Correction Dose is negative (Current BG < Target BG), it implies the patient is below target. The tool subtracts this from the Carb Dose to reduce the insulin given, preventing hypoglycemia. If the total is still negative, carbs are needed without insulin.