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Insulin dosing errors can cause life-threatening hypoglycemia or hyperglycemia. This calculator provides ESTIMATES only. Your actual insulin-to-carb ratio must be determined and adjusted by your diabetes care team based on your individual response. NEVER change your insulin doses without medical guidance.
Educational tool for understanding carb counting and insulin dosing
Total basal + bolus insulin per day. Leave blank to estimate from weight.
The ICR tells you how many grams of carbohydrate one unit of rapid-acting insulin will cover. For example, if your ICR is 1:10, you need 1 unit of insulin for every 10 grams of carbs.
ICR = 500 ÷ Total Daily Dose
Example: TDD = 50 units → ICR = 500/50 = 1:10
The Insulin Sensitivity Factor (also called Correction Factor) tells you how much one unit of insulin will lower your blood glucose. If your ISF is 50, one unit drops BG by 50 mg/dL.
ISF = 1800 ÷ Total Daily Dose
Example: TDD = 50 units → ISF = 1800/50 = 36 mg/dL per unit
Total Bolus = Carb Dose + Correction Dose
Carbs ÷ ICR = Units
Example: 60g carbs ÷ 10 = 6 units
(Current BG - Target BG) ÷ ISF = Units
Example: (180 - 100) ÷ 40 = 2 units
In this example: 6 + 2 = 8 units total
| Food | Serving | Carbs (g) |
|---|---|---|
| Bread | 1 slice | 15g |
| Rice (cooked) | 1/3 cup | 15g |
| Pasta (cooked) | 1/3 cup | 15g |
| Apple | 1 small | 15g |
| Banana | 1/2 medium | 15g |
| Milk | 1 cup | 12g |
| Orange juice | 1/2 cup | 15g |
| Potato | 1 small (3 oz) | 15g |
Hormones like cortisol and growth hormone fluctuate throughout the day, affecting insulin sensitivity. Most people need more insulin in the morning (dawn phenomenon) and may need less later in the day. Your diabetes team will help you identify patterns and set different ratios if needed.
Check your BG 2-3 hours after eating. If you're consistently high, your ICR may be too high (need more insulin). If you're consistently low, it may be too low (need less insulin). Keep food and BG logs to show your diabetes team for adjustments.
With pens, you typically round to the nearest 0.5 or 1 unit. With pumps, you can dose to 0.05 units. For small doses, rounding matters more. Generally, round down if you're concerned about lows, or up if running high. Your diabetes team will guide you.
Yes, but it's complicated. Protein and fat slow carb absorption and can raise BG hours later. Some people (especially on pumps) use extended boluses for high-fat meals. This is advanced and should be discussed with your diabetes team.