What is a correction insulin dose?

A correction dose (also called a supplemental bolus or sliding-scale dose) is the number of insulin units calculated to bring your current blood glucose down to your target. The formula is: (Current BG − Target BG) ÷ Insulin Sensitivity Factor (ISF).

What is the Insulin Sensitivity Factor (ISF)?

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

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

Yes. Select mmol/L from the unit toggle. Ensure your ISF is also expressed in mmol/L units (e.g., 2.8 mmol/L per unit rather than 50 mg/dL per unit). The formula is identical regardless of unit.

What if my current glucose is below my target?

If your current blood glucose is at or below your target, the correction dose is zero. You are already within range — no correction injection is needed. Administering insulin when not above target can cause hypoglycemia.

Should I stack this correction on top of my meal bolus?

That depends on active insulin on board (IOB) and your care plan. If you recently injected a meal bolus, part of it may still be active and lowering your glucose. Consult your endocrinologist or diabetes educator before stacking doses.

Is this calculator a substitute for medical advice?

No. This tool is for educational and estimation purposes only. Insulin needs vary significantly by individual, activity level, illness, and other factors. Always verify doses with your healthcare provider or certified diabetes educator before injecting.

Correction Insulin Dose Calculator

Enter clinician-provided glucose targets and sensitivity factor to check correction-bolus arithmetic; verify the result against the prescribed plan.

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 blood glucose.

Fill in your values and click Calculate Correction Dose

Summary

This tool evaluates (current glucose − target glucose) ÷ insulin sensitivity factor using values already supplied by a diabetes care plan. It does not account for insulin on board, meals, activity, illness, ketones, pump settings, or emergencies and must not create or replace a prescribed dose.

How it works

Select your blood glucose unit (mg/dL or mmol/L).
Enter your current blood glucose reading from your meter or CGM.
Enter your personal target blood glucose (e.g., 100 mg/dL or 5.6 mmol/L).
Enter your Insulin Sensitivity Factor — the number of blood glucose units one unit of insulin lowers you by.
Click Calculate to see your correction dose in insulin units.
If your current glucose is at or below target, the correction dose is zero — no correction needed.

Use cases

Quickly estimate a correction bolus when blood glucose is running high before or between meals.
Double-check a manual correction dose calculation for accuracy.
Educate newly diagnosed patients on how the correction formula works.
Support caregivers managing insulin therapy for a family member.
Evaluate out-of-target CGM readings against personal correction thresholds specified in your diabetes care plan.
Verify pump basal corrections during a pump therapy review.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu