Mealtime Bolus Insulin Calculator
Calculating an accurate mealtime dose requires combining two different mathematical equations: the food dose (based on carbs) and the correction dose (based on current blood sugar). This tool calculates the total recommended bolus dose.
The Math (Manual Calculation)
Step 1 (Food Dose): Carbs / ICR
Step 2 (Correction Dose): (Current BG - Target BG) / ISF
Step 3 (Total Dose): Food Dose + Correction Dose
If you do not know your ICR or ISF, use our Carb Ratio Calculator and Correction Factor Calculator first.
Why It Matters
Proper bolus calculation prevents postprandial spikes. The timing of the bolus is just as important as the dose. For most rapid-acting insulin, taking the dose 15-20 minutes before eating (the "pre-bolus") allows the insulin to peak at the same time the food digests, minimizing spikes.
Common Mistakes
- Forgetting to subtract negative corrections: If your blood sugar is 70 mg/dL (target 100) and you are eating 30g of carbs, you must subtract insulin from the food dose so the carbs bring your blood sugar up to target, rather than keeping you low.
- Not accounting for fat/protein: This calculator only accounts for carbohydrates. High-fat/high-protein meals (like pizza) require different strategies, such as an extended bolus on a pump, as they delay gastric emptying. Read more in our Nutrition Guide.
Frequently Asked Questions (FAQ)
- What if I'm eating a snack?
- If your blood sugar is at target, you only take the Food Dose. If your blood sugar is low, and the snack is intended to treat the low, you do not take insulin for those carbohydrates.