What is a correction bolus?

A correction bolus (also called a sliding-scale dose) is the number of insulin units needed to bring your current blood glucose down to your personal target. It is calculated as: (Current BG − Target BG) ÷ ISF.

What is a meal bolus?

A meal bolus covers the carbohydrates you plan to eat. It is calculated as: Carbohydrates (g) ÷ Carb-to-Insulin Ratio (CIR). If your current glucose is already at target and you are not eating, the meal bolus is zero.

What is the Insulin Sensitivity Factor (ISF)?

ISF (also called correction factor) is how many mg/dL (or mmol/L) one unit of rapid-acting insulin lowers your blood glucose. A common starting estimate is the "1800 Rule" for mg/dL: ISF = 1800 ÷ total daily dose. Ask your diabetes care team for your personal value.

What is the Carb-to-Insulin Ratio (CIR)?

CIR is the number of grams of carbohydrate covered by one unit of insulin. A common starting estimate is the "500 Rule": CIR = 500 ÷ total daily dose. Your actual ratio may vary — confirm with your care team.

Can I use mmol/L instead of mg/dL?

Yes. Select mmol/L from the unit dropdown. The formula is identical — just make sure your ISF is also expressed in mmol/L units (e.g., 2.8 mmol/L per unit instead of 50 mg/dL per unit).

Is this tool a substitute for medical advice?

No. This calculator is for educational and estimation purposes only. Always consult your healthcare provider or certified diabetes educator before changing your insulin doses. Individual factors such as activity, illness, and stress significantly affect insulin needs.

Insulin Dose Calculator

Enter your blood glucose, target, sensitivity factor, and carb intake to calculate your correction and meal bolus insulin doses.

Your Values

Blood Glucose Unit

Current Blood Glucose (mg/dL)

Target Blood Glucose (mg/dL)

Insulin Sensitivity Factor (ISF) (mg/dL per unit)

How much 1 unit of insulin lowers your glucose.

Carb-to-Insulin Ratio (CIR) (g carbs per unit)

Grams of carbohydrate covered by 1 unit of insulin.

Planned Carbohydrate Intake (grams)

Set to 0 for a correction-only dose.

Fill in your values and click Calculate Dose

Summary

This educational tool applies two arithmetic components: a correction estimate and a carbohydrate estimate. It requires a personal target, insulin sensitivity factor (ISF), and carb-to-insulin ratio (CIR) already supplied by the user's diabetes care team. It does not derive or prescribe those settings, account for insulin on board, or authorize an injection.

How it works

Enter your current blood glucose reading (mg/dL or mmol/L).
Set your target blood glucose and select your preferred unit.
Enter your Insulin Sensitivity Factor (ISF) — how much one unit of insulin lowers glucose.
Enter your Carb-to-Insulin Ratio (CIR) — grams of carbohydrate covered by 1 unit of insulin.
Enter the grams of carbohydrates you plan to eat (leave at 0 for a correction-only dose).
The calculator displays the arithmetic correction, meal, and combined estimates.

Use cases

Quickly estimate a correction bolus before a meal when running high.
Calculate a meal bolus for a known carbohydrate serving.
Review arithmetic that combines correction and meal components using clinician-provided settings.
Double-check manual dose calculations for accuracy.
Educate newly diagnosed patients on the sliding-scale concept.
Support caregivers managing insulin therapy for a family member.
Use as a reference during continuous glucose monitoring (CGM) reviews.
Verify pump settings during an insulin pump therapy adjustment.

Frequently Asked Questions

Last updated: 2026-09-30 · Reviewed by Nham Vu