Insulin initiation & adjustment worksheet

Calculate a weight-based total daily insulin dose, split it into basal and mealtime components, and derive the insulin-to-carbohydrate ratio, correction factor, and a correction dose — all from a single weight entry.

High-consequence calculationInsulin is a high-alert medication and a leading cause of medication-related hypoglycaemia and emergency admissions. Every figure produced here is a starting estimate requiring individualised titration against glucose readings.

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What is this for?

Insulin initiation in type 1 diabetes conventionally starts at 0.5 units/kg/day, divided half as basal and half as rapid-acting split across meals. From that total daily dose, the rule of 450 or 500 gives the carbohydrate covered by one unit, and the 1500 or 1800 rule gives the glucose drop produced by one unit. This worksheet links all of them.

How to use it

Enter the patient's weight and select a starting dose per kilogram — 0.5 units/kg/day is the conventional type 1 initiation.
Select whether mealtime insulin is rapid-acting or regular; this determines which pair of rules is applied.
If the patient is already established on insulin, enter their actual total daily dose in the override field — the ratios will then be based on their real requirement rather than a weight estimate.
To calculate a correction dose, add the current and target glucose values.

Worked example

A newly diagnosed 70 kg adult with type 1 diabetes is starting rapid-acting basal-bolus insulin. Their glucose is currently 250 mg/dL with a target of 120 mg/dL.

Answer: TDD = 70 × 0.5 = 35 units. Basal 17.5 units, mealtime 17.5 units total, so roughly 6 units per meal. ICR = 500 ÷ 35 = 1 unit per 14 g carbohydrate. Correction factor = 1800 ÷ 35 = 51 mg/dL per unit. Correction dose = (250 − 120) ÷ 51 = 2.5 units.

Clinical pearls & pitfalls

The rule pair must match the insulin. Rapid-acting analogues use 500 and 1800; regular insulin uses 450 and 1500. Mixing them across types gives ratios that are systematically wrong.
All four rules key off the total daily dose, so an inaccurate TDD propagates into every subsequent figure. If the patient is already on insulin, use their actual TDD rather than a weight-based estimate.
The correction dose is added to the mealtime carbohydrate-coverage dose, not given instead of it.
Account for insulin on board. Stacking correction doses before the previous one has finished acting is a common route to hypoglycaemia — rapid-acting insulin acts for roughly four hours.
Newly diagnosed type 1 patients often enter a honeymoon phase with markedly reduced requirements. Doses calculated at diagnosis may need substantial reduction within weeks.
Corticosteroids, infection, and pregnancy all raise requirements substantially; exercise and renal impairment lower them.

Assumptions & limitations

The 450/500 and 1500/1800 rules are empirical heuristics derived from populations of adults with type 1 diabetes. Individual ratios frequently differ substantially and are established by observation over days to weeks.
The 50/50 basal-to-bolus split is a starting convention. Actual requirements often depart from it, particularly in type 2 diabetes and in people with irregular eating patterns.
Not validated for children, in pregnancy, in diabetic ketoacidosis, or for insulin pump basal-rate programming, all of which require specialist protocols.
The correction factor assumes a linear glucose response to insulin, which does not hold at very high or very low glucose concentrations.

References

American Diabetes Association Professional Practice Committee. 9. Pharmacologic approaches to glycemic treatment: Standards of Care in Diabetes — 2025. Diabetes Care. 2025;48(Suppl 1):S181-S206.
Walsh J, Roberts R, Bailey T. Guidelines for insulin dosing in continuous subcutaneous insulin infusion using new formulas from a retrospective study. J Diabetes Sci Technol. 2010;4(5):1174-1181.
Institute for Safe Medication Practices. ISMP List of High-Alert Medications in Acute Care Settings.