Insulin Dose
Calculator

Insulin is the primary treatment for Type 1 diabetes mellitus (T1DM) and is used in many patients with Type 2 diabetes mellitus (T2DM) when glycaemic targets cannot be achieved with oral agents alone. Insulin management involves several interconnected calculations — total daily dose estimation, basal/bolus split, insulin-to-carbohydrate ratio, and correction (sensitivity) factor — all of which require precision.

Modern intensive insulin therapy uses a basal-bolus framework: a long-acting (basal) insulin covers background needs, while rapid-acting (bolus) insulin is given with meals and to correct high glucose levels. Each component must be individually calibrated to the patient's physiology, diet, and lifestyle.

This calculator provides evidence-based starting estimates for each component of an insulin regimen, along with a correction dose calculator for episodic hyperglycaemia. All values are starting points that require clinical oversight and ongoing titration.

The four core calculations in insulin management use well-established formulas, each building on the total daily dose (TDD):

Enter the patient's weight, diabetes type (T1 or T2), and select a TDD preset from the preset list for the applicable clinical scenario. The tool computes the daily dose in units, the basal and bolus split, the ISF, and an ICR estimate (insulin-to-carbohydrate ratio based on the '500 rule').

A correction dose calculator accepts the current blood glucose and target blood glucose, applying the ISF to generate a correction bolus recommendation.

Insulin-on-board (IOB) — pre-existing active insulin from a previous bolus — can be subtracted from the correction dose, with an inline warning when the IOB adjustment reduces the correction below zero (preventing a dose that would cause hypoglycaemia).

Persistent safety warnings appear for: TDD over 1 U/kg/day in T1DM or 2 U/kg/day in T2DM (flag for clinical review); correction doses exceeding a safe single-bolus threshold; and reminders that all values require diabetes care team validation before implementation.

Session history records each calculation with the weight, diabetes type, TDD, and result, exportable to CSV for documentation.

Newly diagnosed T1DM / Honeymoon phase (0.4 U/kg/day): During the partial remission ('honeymoon') period, residual beta-cell function reduces exogenous insulin requirements. Starting at 0.4 U/kg/day minimises hypoglycaemia risk while preserving beta-cell function.

Typical stable T1DM (0.5 U/kg/day): The most commonly cited starting point for adults with established T1DM. This may increase to 0.7–1.0 U/kg/day in adolescents, during illness, or in the setting of insulin resistance.

High requirement / Adolescent T1DM (0.7–1.0 U/kg/day): Puberty significantly increases insulin resistance through growth hormone and IGF-1 effects. Higher TDD requirements during adolescence are normal and should not prompt unnecessary clinical concern.

T2DM initiation (0.2–0.3 U/kg/day): T2DM insulin initiation typically starts with basal insulin only (0.1–0.2 U/kg/day of long-acting insulin at bedtime), with bolus insulin added if glycaemic targets are not met. Full basal-bolus therapy is introduced progressively.

Hypoglycaemia is the most dangerous immediate consequence of insulin therapy. Blood glucose below 4 mmol/L (72 mg/dL) constitutes hypoglycaemia; below 3 mmol/L (54 mg/dL) is clinically significant and requires prompt treatment.

Risk factors for insulin-induced hypoglycaemia include: excessive dose, missed or delayed meals, unusual physical activity, alcohol consumption, incorrect injection technique (e.g., injecting into muscle rather than subcutaneous tissue), and impaired awareness of hypoglycaemia (hypoglycaemia unawareness).

All patients on insulin should carry fast-acting glucose at all times (glucose tablets, sugary drink, or gel) and be educated to recognise early warning symptoms: sweating, palpitations, tremor, hunger, confusion, and dizziness.