🧬 Insulin Correction Factor / Carb Ratio
Estimates the insulin sensitivity (correction) factor and insulin-to-carbohydrate ratio from total daily dose, providing starting points for bolus dosing in intensive insulin therapy.
The 1800/500 ('rapid') and 1500/450 ('regular') rules are starting estimates derived from TDD, not validated individual targets — always refine empirically. (original synthesis · not guideline verbatim)
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When to use
Enter total daily dose and select rapid- or short-acting insulin; the tool returns ISF (mmol/L and mg/dL per unit) and ICR (grams per unit). Titrate both against the patient's own glucose monitoring.
How it works
Rapid-acting: ISF = 1800/TDD (mg/dL per U), ICR = 500/TDD (g per U). Short-acting: ISF = 1500/TDD, ICR = 450/TDD. ISF in mmol/L = (mg/dL value)/18.
Key points
- The 1800/500 ('rapid') and 1500/450 ('regular') rules are starting estimates derived from TDD, not validated individual targets — always refine empirically. (original synthesis · not guideline verbatim)
- Both factors scale inversely with TDD, so a recent dose change invalidates a previously derived ISF/ICR.
- Apply with caution in hypoglycemia-prone patients; specialist supervision and structured education underpin safe carb counting.
References
- Walsh J, Roberts R, Bailey T. Guidelines for optimal bolus calculator settings in adults. J Diabetes Sci Technol. 2011;5(1):129-135.
- ADA. Standards of Care in Diabetes — Pharmacologic Approaches to Glycemic Treatment. Diabetes Care. 2024;47(Suppl 1):S158-S178.
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| Total daily insulin dose TDD | 40 U/day |
|---|---|
| Insulin type | Rapid-acting (1800/500) |
→Correction factor ISF2.5mmol/L/U
- ISF：45 mg/dL/U
- Carb ratio ICR：1 U : 13 g
| Total daily insulin dose TDD | 40 U/day |
|---|---|
| Insulin type | Regular/short-acting (1500/450) |
→Correction factor ISF2.1mmol/L/U
- ISF：38 mg/dL/U
- Carb ratio ICR：1 U : 11 g
Frequently asked questions
- What is Insulin Correction Factor / Carb Ratio?
- Estimates the insulin sensitivity (correction) factor and insulin-to-carbohydrate ratio from total daily dose, providing starting points for bolus dosing in intensive insulin therapy.
- How is Insulin Correction Factor / Carb Ratio calculated? What is the core formula?
- Rapid-acting: ISF = 1800/TDD (mg/dL per U), ICR = 500/TDD (g per U). Short-acting: ISF = 1500/TDD, ICR = 450/TDD. ISF in mmol/L = (mg/dL value)/18.
- When is Insulin Correction Factor / Carb Ratio used?
- Enter total daily dose and select rapid- or short-acting insulin; the tool returns ISF (mmol/L and mg/dL per unit) and ICR (grams per unit). Titrate both against the patient's own glucose monitoring.
- What are the key clinical points for Insulin Correction Factor / Carb Ratio?
- The 1800/500 ('rapid') and 1500/450 ('regular') rules are starting estimates derived from TDD, not validated individual targets — always refine empirically. (original synthesis · not guideline verbatim) Both factors scale inversely with TDD, so a recent dose change invalidates a previously derived ISF/ICR. Apply with caution in hypoglycemia-prone patients; specialist supervision and structured education underpin safe carb counting.
- What are the limits and cautions when using Insulin Correction Factor / Carb Ratio?
- For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.
- How is Insulin Correction Factor / Carb Ratio calculated in practice? Can you show a worked example?
- Inputs: Total daily insulin dose TDD 40 U/day, Insulin type Rapid-acting (1800/500) → Result: Correction factor ISF 2.5 mmol/L/U（ISF: 45 mg/dL/U, Carb ratio ICR: 1 U : 13 g） Inputs: Total daily insulin dose TDD 40 U/day, Insulin type Regular/short-acting (1500/450) → Result: Correction factor ISF 2.1 mmol/L/U（ISF: 38 mg/dL/U, Carb ratio ICR: 1 U : 11 g）