Correction Factor Calculator
Find out how many mg/dL (or mmol/L) one unit of insulin will lower your blood glucose - essential for safe correction dosing.
Educational estimator only - not medical advice.
Typical range: 10-150 units/day
Rapid-acting: Humalog, Novolog, Fiasp, Lyumjev - uses the 1800 Rule
Enter your Total Daily Dose above to calculate your Correction Factor.
The Correction Factor (CF), also called the Insulin Sensitivity Factor (ISF), tells you how much one unit of insulin will lower your blood glucose. There are two widely used formulas depending on insulin type:
The difference between 1800 and 1500 reflects the stronger, faster peak of modern rapid-acting analogs compared to older regular insulin. For mmol/L results, the equivalents are approximately 100 / TDD (rapid) and 83 / TDD (regular).
Your CF is used to calculate a correction dose: if your blood glucose is 50 mg/dL above target and your CF is 50 mg/dL, you would take 1 unit to bring it back to target.
CFs vary throughout the day (typically lower in the morning), can change with illness, stress, activity, and hormonal cycles, and should be tested and verified with your healthcare provider.
Understanding your correction factor is fundamental to safe insulin management. Learn how to test, refine, and apply it - plus when and how correction doses interact with mealtime insulin - in the FOD Trilogy.
Deep Dive: FOD Trilogy - Ch 11This calculator provides an estimated starting point only. Using an incorrect correction factor can cause dangerous hypoglycemia (dangerously low blood sugar) or hyperglycemia. Correction factors must be individually tested and verified under the supervision of a qualified healthcare provider or certified diabetes educator. Never use this result to make insulin dosing decisions without medical guidance. Do not use this tool if you are experiencing a medical emergency - contact your healthcare provider immediately.