Insulin Sensitivity Factor Calculator

Calculate your Insulin Sensitivity Factor (ISF) to find out how many mg/dL one unit of insulin lowers your blood glucose.

Use the Insulin Sensitivity Factor Calculator

Enter Your Insulin Data

Sum of all basal + bolus units per day (3–7 day average recommended).

Insulin Type

Used to calculate a sample correction dose if your current BG is above target.

Typical ISF Ranges

Insulin-sensitive (e.g. child, lean type 1) 50–100 mg/dL/unit
Typical adult type 1 30–50 mg/dL/unit
Adult with insulin resistance 15–30 mg/dL/unit
High resistance / large TDI < 15 mg/dL/unit

These are rough benchmarks. Individual ISF depends on activity, stress, illness, and other factors.

Medical disclaimer: This tool provides an educational estimate only. Do not adjust insulin doses without guidance from a licensed healthcare provider.

Summary

The Insulin Sensitivity Factor (ISF) — also called correction factor — tells you how many mg/dL one unit of insulin lowers blood glucose. This calculator uses the 1800 Rule for regular insulin and the 1700 Rule for rapid-acting analogs, dividing that constant by your Total Daily Insulin dose. The result is a starting estimate for correction dosing; individual response varies, so verify with your care team.

How it works

  1. Enter your Total Daily Insulin (TDI) — the sum of all basal and bolus insulin units you take per day.
  2. Select your insulin type: rapid-acting (e.g. Humalog, NovoLog, Apidra) or regular (e.g. Humulin R).
  3. The calculator applies the appropriate rule: 1700 ÷ TDI for rapid-acting, or 1800 ÷ TDI for regular insulin.
  4. Your ISF is displayed in mg/dL per unit — meaning one unit of insulin lowers blood glucose by that amount.
  5. Use the result as a starting point; always confirm your ISF with your healthcare provider.

Use cases

  • Estimating a correction dose when blood glucose is above target.
  • Verifying whether your current correction factor aligns with the 1800/1700 rule.
  • Adjusting insulin therapy when total daily dose changes.
  • Teaching patients or students how ISF is derived from TDI.
  • Comparing ISF across different insulin types.
  • Supporting diabetes educators and endocrinologists in clinical discussions.

Frequently Asked Questions

Last updated: 2026-06-14 · Reviewed by Nham Vu