Last verified · v1.0

Calculator · health

Insulin Dosage Calculator

Calculate total daily insulin, basal, bolus, correction doses, and carb ratios by weight and patient type using validated clinical dosing formulas.

FreeInstantNo signupOpen source

Inputs

Body Weight

Weight Unit

Patient Type / Condition

Calculation Output

Insulin Dose

—

Get a plain-English breakdown of your result with practical next steps.

Insulin Dose—units

The formula

How the
result is
computed.

How the Insulin Dosage Calculator Works

The insulin dosage calculator estimates a patient's Total Daily Insulin (TDI) requirement using a clinically validated weight-based formula adopted across major diabetes care institutions. The core equation is:

TDI (units/day) = Body Weight (kg) × Factor (F)

Factor F is not a fixed universal value. It captures the wide variation in insulin sensitivity across patient populations, disease stages, and physiological conditions. Selecting the correct factor is the most consequential step in deriving a safe starting dose.

Factor Values by Patient Type

Type 2 diabetes — conservative initiation: F = 0.1–0.2 units/kg. Recommended for insulin-naive patients with residual beta-cell function to minimize hypoglycemia risk, per Stanford's Type 2 Diabetes Adult Outpatient Insulin Guidelines.
Type 2 diabetes — standard initiation: F = 0.5 units/kg. A broadly used starting dose that balances efficacy and safety in most outpatient settings.
Type 2 diabetes — insulin resistant: F = 0.7–1.0 units/kg. Patients with significant obesity, HbA1c above 9%, or long disease duration typically require higher doses due to peripheral resistance.
Type 1 diabetes — established regimen: F = 0.5–0.7 units/kg. The majority of Type 1 adults fall within this range once therapy is titrated to target.
Type 1 diabetes — honeymoon phase: F = 0.4 units/kg. Residual endogenous insulin secretion during the honeymoon period substantially reduces exogenous requirements.
Pediatric (prepubertal): F = 0.5–0.7 units/kg. Children generally require lower weight-adjusted doses than adults.
Pediatric (pubertal): F = 0.7–1.0 units/kg. Growth-hormone surges during puberty markedly increase insulin resistance and raise requirements.
Gestational diabetes / pregnancy: F = 0.7–1.0 units/kg by trimester. The University of Cincinnati's Diabetes and Pregnancy Pocket Guide recommends 0.7–0.8 units/kg in the second trimester and 0.9–1.0 units/kg in the third trimester as placental insulin resistance increases.

Basal and Bolus Distribution

After computing TDI, clinical practice divides it into basal and bolus components using the standard 50/50 rule, as described by the UCSF Diabetes Teaching Center:

Basal insulin: 50% of TDI — administered once or twice daily as long-acting insulin (glargine, detemir, or degludec)
Bolus insulin per meal: 50% of TDI divided across 3 meals — given before each meal as rapid-acting insulin (lispro, aspart, or glulisine)

Worked example: A 75 kg patient with established Type 1 diabetes, using F = 0.6: TDI = 75 × 0.6 = 45 units/day. Basal = 22–23 units/day. Bolus per meal = 7–8 units per meal.

Insulin Sensitivity Factor (Correction Factor)

The Insulin Sensitivity Factor (ISF) predicts how many mg/dL one unit of insulin will lower blood glucose. Two established rules apply based on insulin type:

Rule of 1700 (rapid-acting analogs): ISF = 1700 ÷ TDI
Rule of 1500 (regular human insulin): ISF = 1500 ÷ TDI

For the 45-unit TDI example using a rapid-acting analog: ISF = 1700 ÷ 45 ≈ 38 mg/dL per unit. If blood glucose is 220 mg/dL and the target is 100 mg/dL, the correction dose = (220 − 100) ÷ 38 ≈ 3 units.

Insulin-to-Carbohydrate Ratio (ICR)

The Rule of 500 estimates how many grams of carbohydrate one unit of insulin covers:

ICR = 500 ÷ TDI

For a TDI of 45 units: ICR = 500 ÷ 45 ≈ 11 grams of carbohydrate per unit. A meal containing 55 g of carbohydrates requires 55 ÷ 11 = 5 units of bolus insulin. Research published in PMC's review of insulin-dosing formulas for continuous subcutaneous insulin infusion (CSII) confirms these weight-based ratios are the standard starting foundation for CSII pump programming as well as multiple daily injection regimens.

Important Clinical Limitations

All calculator outputs are starting estimates requiring systematic titration through self-monitored blood glucose (SMBG) or continuous glucose monitor (CGM) data over days to weeks.
Renal impairment, hepatic disease, corticosteroid therapy, and intercurrent illness can cause actual insulin requirements to deviate 20–40% from initial weight-based estimates.
Insulin needs are dynamic — activity level, dietary composition, hormonal cycles, and disease progression all affect sensitivity and require periodic recalculation.
These calculations do not substitute for individualized clinical assessment. Always consult a licensed healthcare provider before initiating or adjusting any insulin regimen.

Reference

Frequently asked questions

What is Total Daily Insulin (TDI) and how does the calculator compute it?

Total Daily Insulin (TDI) is the estimated number of insulin units a patient requires across 24 hours, covering both background and mealtime needs. The calculator multiplies body weight in kilograms by a patient-type factor (F). For example, a 70 kg patient with established Type 1 diabetes using F = 0.6 yields a TDI of 42 units per day. TDI then serves as the foundation for deriving basal dose, bolus dose per meal, correction factor, and insulin-to-carbohydrate ratio.

What insulin dosage factor should a newly diagnosed Type 2 diabetic use?

Newly diagnosed Type 2 patients typically start at 0.1–0.2 units/kg for a very conservative initiation or 0.5 units/kg for a standard start, according to Stanford's Type 2 Diabetes Adult Outpatient Insulin Guidelines. A 90 kg patient at 0.5 units/kg would begin at 45 units/day, then titrate upward by 2–4 units every 3 days until fasting glucose consistently falls within the target range of 80–130 mg/dL.

How does the calculator split TDI into basal and bolus insulin doses?

The standard 50/50 rule divides TDI equally between basal and bolus components. The basal half is administered as a single long-acting injection (e.g., glargine or degludec), while the bolus half is divided across three meals, providing roughly 16–17% of TDI before each meal. For a TDI of 48 units, basal equals 24 units per day and each mealtime bolus equals 8 units, consistent with UCSF Diabetes Teaching Center guidelines.

What is the Rule of 1700 and how does the correction factor work?

The Rule of 1700 applies to rapid-acting insulin analogs: Insulin Sensitivity Factor (ISF) = 1700 divided by TDI. The ISF tells clinicians how many mg/dL a single unit of insulin will lower blood glucose. With a TDI of 50 units, ISF = 34 mg/dL per unit. A patient whose glucose is 238 mg/dL targeting 100 mg/dL needs a correction of (238 minus 100) divided by 34, approximately 4 units. For regular human insulin, the Rule of 1500 applies instead of 1700.

Can pregnant women safely use the insulin dosage calculator?

The calculator includes pregnancy-specific factor values grounded in clinical guidelines. Second-trimester patients use F = 0.7–0.8 units/kg; third-trimester patients use F = 0.9–1.0 units/kg as placental insulin resistance intensifies, per the University of Cincinnati Diabetes and Pregnancy Pocket Guide. Because insulin requirements during pregnancy shift rapidly week to week, pregnant patients must work with an endocrinologist or maternal-fetal medicine specialist for continuous monitoring and dose titration — the calculator output is a starting point only.

How accurate are weight-based insulin dosing formulas in clinical practice?

Weight-based formulas provide clinically reliable starting estimates, though individual response varies. Research published in PMC's review of insulin-dosing formulas for CSII found that TDI calculations correlate well with eventual optimized doses across both Type 1 and Type 2 populations. However, factors such as renal function, physical activity level, dietary carbohydrate load, and concurrent medications (especially corticosteroids) can cause actual insulin needs to deviate 20–40% from the initial weight-based estimate, making structured titration over 1–2 weeks essential for safe glycemic control.