Understanding Carb-to-Insulin Ratios

The carb-to-insulin ratio (CIR) indicates how many grams of carbohydrates are covered by 1 unit of insulin. This calculator uses the 500 Rule: divide 500 by your total daily insulin dose to estimate your ratio.

Example Calculation

If your total daily insulin is 50 units: 500 ÷ 50 = 10. Your estimated ratio is 1 unit per 10g carbs.

Reference Table

Total Daily Insulin	Ratio (g carbs/unit)
20 units	1:25
30 units	1:17
40 units	1:12.5
50 units	1:10

Note: These are estimates. Individual ratios vary based on sensitivity, activity, and other factors.

Frequently Asked Questions

Is the 500 Rule accurate for everyone?

No. The 500 Rule is a starting point. Individual ratios should be fine-tuned with medical guidance.

Should I round my ratio?

Yes. Ratios are typically rounded to the nearest whole number or half-unit for practicality.

What if I use mixed insulin types?

Consult your healthcare provider. This calculator is for rapid-acting insulin only.

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Carb-to-Insulin Ratio Calculator

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