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🍽️ Insulin:Carb Ratio Calculator

Calculate how many grams of carbohydrate one unit of rapid-acting insulin covers.

Corrected Calcium Fructosamine → A1C Insulin:Carb Ratio Insulin Sensitivity Sliding Scale

Insulin-to-Carbohydrate Ratio (ICR)

The ICR tells you how many grams of carbohydrate are covered by 1 unit of rapid-acting insulin. It is used to calculate mealtime (bolus) insulin doses. The "500 Rule" is the most common starting formula for rapid-acting insulin analogues (lispro, aspart, glulisine).

Add all insulin: basal + all bolus doses over a typical 24-hour period.
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Grams of carb per 1 unit of insulin
500 Rule (rapid-acting): ICR = 500 ÷ TDD
450 Rule (regular insulin): ICR = 450 ÷ TDD

How to use your ICR: Mealtime dose = (Carbohydrates in meal ÷ ICR)
Example: If ICR = 10, and meal has 60g carbs → give 6 units pre-meal
In the Houston area?

Have questions about insulin dosing? See an endocrinologist.

Insulin pump and CGM care, dose adjustments, at Endocrine & Diabetes Plus in Sugar Land and Memorial City. New patients are usually seen within 2 weeks; the earliest openings are with Dr. Chhavi Chadha. Telehealth follow-ups for patients anywhere in Texas.

Outside Texas? Share this result with your own doctor. This tool is for information only.
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⚕️ Important: This calculator provides a starting estimate only. Your actual ICR may vary by time of day (often different at breakfast vs. dinner), stress level, activity, and illness. ICR should always be confirmed and adjusted by your diabetes care team based on blood glucose response. Never adjust insulin doses without guidance from your provider.