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Insulin Correction Dose Calculator

Calculate how much rapid-acting insulin is needed to bring high blood sugar back to a target range.

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Formula

(Current Glucose - Target) / Sensitivity Factor

Determines the units of insulin required based on your individual Insulin Sensitivity Factor (ISF).

Worked Example

Current 250, Target 100, Sensitivity 50 -> Give 3 units of insulin.

How Insulin Correction Doses Work

A correction dose of insulin is used to bring high blood sugar back toward a target level. The dose depends on how far above target you are and how sensitive your body is to insulin.
  • Formula: Correction Dose = (Current Blood Sugar - Target) / Insulin Sensitivity Factor
  • The 1800 Rule estimates ISF for rapid-acting insulin: ISF = 1800 / Total Daily Dose
  • The 1500 Rule estimates ISF for regular insulin: ISF = 1500 / Total Daily Dose
  • Wait at least 3 to 4 hours between correction doses to avoid insulin stacking
  • Typical ISF range: 25 to 75 mg/dL per unit, depending on insulin resistance

This tool provides estimates only. Always follow your prescriber's individualized dosing instructions and consult before making changes.

You can also calculate changes using our Carbohydrate Ratio Calculator or HbA1c to eAG Calculator.

Frequently Asked Questions

What is the Insulin Sensitivity Factor?

The Insulin Sensitivity Factor (ISF), also called the Correction Factor, is how much one unit of rapid-acting insulin will lower your blood sugar. For example, an ISF of 50 means one unit drops you by 50 mg/dL.

How is ISF estimated?

For rapid-acting insulin, the 1800 Rule divides 1800 by your Total Daily Dose (TDD). For regular insulin, the 1500 Rule divides 1500 by TDD. For example, a TDD of 40 units gives an ISF of 45 mg/dL per unit with rapid-acting insulin.

What is insulin stacking?

Insulin stacking occurs when a new correction dose is given before the previous dose has fully acted, typically within 3 to 4 hours. This can cause dangerous hypoglycemia (low blood sugar below 70 mg/dL).

What is Insulin on Board?

Insulin on Board (IOB) is the amount of insulin still active from a previous dose. Most rapid-acting insulin has a duration of action of 4 to 5 hours, so IOB should be subtracted from new corrections.

What is a typical target blood sugar?

Most adults target 100 to 120 mg/dL before meals, though targets vary. Older adults or those with hypoglycemia unawareness may have a higher target of 120 to 150 mg/dL.

Should I correct every high reading?

Follow your doctor's protocol. Many plans only correct when blood sugar exceeds 150 mg/dL and allow at least 3 to 4 hours between corrections to account for active insulin.

Medical Disclaimer

This calculator is provided for informational and educational purposes only. It is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making any decisions based on these results. Do not disregard or delay seeking medical advice because of information obtained from this tool.

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