Insulin Correction Dose Calculator
Estimate how many units of rapid-acting insulin are needed to bring a high blood glucose back to your target. Uses the formula: (Current BG − Target BG) ÷ ISF. Educational use only — always account for active insulin on board.
🎯 Correction Dose Calculator
ADA general target: 80–130 mg/dL before meals.
Don't know your ISF? Calculate ISF →
Correction Dose Estimate
mg/dL
mg/dL per unit
correction (no IOB)
not included
The Correction Dose Formula
Correction Dose Formula
Example: Current BG = 250 mg/dL, Target = 100 mg/dL, ISF = 50 → Correction = (250 − 100) ÷ 50 = 3 units. This is the dose needed to bring BG from 250 to 100 if ISF is accurate and there is no IOB.
⚠️ Critical: Insulin on Board (IOB)
Rapid-acting insulin analogs remain active for 3–5 hours after injection. If you gave a correction 2 hours ago, perhaps half of that dose is still working. Adding a full new correction on top creates "insulin stacking" — a major cause of dangerous hypoglycemia.
Before correcting:
- When did you last take rapid-acting insulin?
- Estimate how much of that dose is still active (typical activity curve peaks at 1–2 hours, mostly gone by 4 hours)
- Subtract the estimated IOB from your correction dose
- Insulin pumps with bolus calculators do this automatically
This calculator does not model insulin on board. It shows the full correction dose assuming no active insulin. Always subtract IOB before giving a correction dose. If your pump or bolus calculator shows an IOB, use that instead.
Sources & References
- Walsh J, Roberts R, Bailey T. "Guidelines for Optimal Bolus Calculator Settings." J Diabetes Sci Technol. 2011;5(1):129–135.
- American Diabetes Association. Standards of Medical Care in Diabetes — 2024. Section 7. Link
Last reviewed: June 2025
Frequently Asked Questions
How do I calculate an insulin correction dose?
Correction dose = (Current BG − Target BG) ÷ ISF. With BG = 250, target = 100, ISF = 50: correction = 3 units. This is the dose needed to bring BG to target assuming no active insulin on board. Always subtract IOB before giving a correction to avoid hypoglycemia from stacking. Confirm your correction approach with your diabetes care team.
What is insulin on board (IOB) and why does it matter?
IOB is the amount of rapid-acting insulin still active from a previous injection. Rapid-acting analogs remain active 3–5 hours, peaking at 1–2 hours. If you correct without subtracting IOB, you stack insulin — the previous dose is still lowering BG, and the new dose pushes it even lower, risking severe hypoglycemia. Most insulin pumps track IOB automatically. For MDI patients, mentally subtract estimated active insulin from correction dose, or wait until previous dose has cleared (≥ 4 hours).
When should I give a correction dose?
Correct when BG is above your target and you have little or no IOB. Most guidelines suggest waiting at least 3–4 hours after the last rapid-acting dose before correcting again. Before meals, many bolus calculators add a correction component to the meal bolus if BG is above target — this counts as a correction. At bedtime, be conservative with corrections (use half the calculated dose or avoid correcting unless very high) to prevent overnight hypoglycemia.
What BG level requires emergency care?
BG above 300 mg/dL (16.7 mmol/L) with symptoms of DKA — nausea, vomiting, abdominal pain, fruity or acetone breath, difficulty breathing, extreme fatigue — requires emergency evaluation. Do not attempt to manage DKA at home with correction doses alone. DKA requires IV fluids, insulin infusion, and electrolyte replacement in a hospital. Call 911 or go to an emergency department immediately. Type 1 patients are at higher DKA risk, but Type 2 and others can develop it too.