What this calculator does
The Insulin Dose Calculator estimates a mealtime (bolus) dose of rapid-acting insulin by combining two parts: the insulin needed to cover the carbohydrates you are about to eat, and a correction dose to bring an elevated blood glucose back toward your target. It is an educational tool that illustrates the standard bolus formula used in intensive insulin therapy. It is not medical advice and does not replace the dosing plan from your healthcare provider.
How to use it
Enter the grams of carbohydrate in your meal, your personal insulin-to-carb ratio (ICR), your current and target blood glucose in mg/dL, and your correction factor (ISF). These ratios are highly individual and are set by your diabetes care team. The calculator returns the meal dose, the correction dose, and the total.
The formula
The total dose adds the carb-covering dose to the correction dose:
$$\text{Dose} = \frac{\text{Carbs}}{\text{ICR}} + \frac{\text{BG}_{current} - \text{BG}_{target}}{\text{ISF}}$$Here \(\text{ICR}\) is the grams of carbohydrate covered by one unit, and \(\text{ISF}\) is the mg/dL that one unit is expected to lower blood glucose. If the current glucose is at or below target, the correction term is treated as \(0\) (no negative correction).
Worked example
Suppose a meal contains \(60\,\text{g}\) of carbs with an ICR of \(10\), and blood glucose is \(180\) mg/dL with a target of \(120\) and an ISF of \(50\).
$$\text{Meal} = \frac{60}{10} = 6\ \text{units}$$$$\text{Correction} = \frac{180 - 120}{50} = 1.2\ \text{units}$$$$\text{Dose} = 6 + 1.2 = 7.2\ \text{units}$$FAQ
What is an insulin-to-carb ratio? It is how many grams of carbohydrate one unit of insulin covers. An ICR of 1:10 means 1 unit per 10 g.
What is the correction (sensitivity) factor? It is how many mg/dL one unit of insulin is expected to lower your blood glucose, often estimated with the "1800 rule" for rapid-acting insulin.
Can I rely on this to dose myself? No. Active insulin, exercise, illness, and many other factors change real dosing. Always follow your prescribed plan and consult your care team.
