How do you calculate an insulin dose?

A bolus insulin dose has two parts: a meal dose (carbs eaten ÷ insulin-to-carb ratio) plus a correction dose ((current blood glucose − target) ÷ insulin sensitivity factor). Add both for the total units to inject.

How is insulin sensitivity factor (ISF) calculated?

Use the 1800 rule for rapid-acting insulin: ISF (mg/dL drop per unit) = 1800 ÷ total daily dose (TDD). For mmol/L use the 100 rule: ISF = 100 ÷ TDD.

How do you calculate total daily insulin dose (TDD)?

A starting estimate is 0.5 units of insulin per kilogram of body weight per day. Roughly 50% is given as basal (long-acting) and 50% as bolus (rapid-acting) divided across meals.

What is HOMA-IR and how is it calculated?

HOMA-IR (Homeostatic Model Assessment of Insulin Resistance) = (fasting insulin µIU/mL × fasting glucose mg/dL) ÷ 405. Values under 1.0 are optimal; over 2.5 suggests insulin resistance.

Is 20 units of insulin a lot?

It depends on body weight, insulin type, and whether it's basal or bolus. A 70 kg adult on intensive therapy might use 30–50 units of basal insulin daily. Always follow your healthcare provider's plan.

Insulin Calculator

Calculate insulin dosing, assess insulin resistance (HOMA-IR), and determine total daily dose (TDD) with accurate formulas.

Calculator Type

Bolus Insulin Dosing

Current Blood Glucose (mg/dL):

Target Blood Glucose (mg/dL):

Carbohydrates (grams):

Insulin-to-Carb Ratio (I:C):

Correction Factor (ISF):

Calculated Insulin Dose

Correction Dose

1.60

units

Meal Dose

4.00

units

Total Bolus

5.60

units

Formulas Used:

Correction Dose = (Current BG - Target BG) ÷ ISFMeal Dose = Total Carbs ÷ I:C RatioTotal Bolus = Correction Dose + Meal Dose

Important Safety Notes:

• Always consult your healthcare provider before adjusting insulin doses
• This calculator provides estimates - your actual needs may vary
• Consider IOB (insulin on board) to avoid stacking
• Account for exercise, stress, illness that affect insulin needs

Insulin Science & Management

Understanding Insulin Types

• Rapid-Acting (Bolus): Onset 10-15 min, peak 1-2h, duration 3-5h (Humalog, NovoLog, Apidra)
• Short-Acting (Regular): Onset 30 min, peak 2-4h, duration 5-8h
• Intermediate (NPH): Onset 1-2h, peak 4-8h, duration 12-16h
• Long-Acting (Basal): Onset 1-2h, no peak, duration 20-24h (Lantus, Levemir, Tresiba)

Key Ratios Explained

• I:C Ratio: Units of insulin needed per grams of carbs (e.g., 1:15 = 1 unit per 15g carbs)
• ISF (Correction Factor): How much 1 unit lowers blood glucose (e.g., 1:50 = 1 unit drops BG by 50 mg/dL)
• Rule of 500: I:C Ratio = 500 ÷ TDD
• Rule of 1800: ISF = 1800 ÷ TDD

Improving Insulin Sensitivity

✓ Regular exercise (especially strength training)
✓ Low-carb or Mediterranean diet
✓ Adequate sleep (7-9 hours)
✓ Stress management
✓ Intermittent fasting
✓ Maintain healthy weight
✓ Avoid processed foods and added sugars

Medical Disclaimer:

This calculator is for educational purposes only and not a substitute for professional medical advice. Never adjust insulin doses without consulting your healthcare provider. Incorrect insulin dosing can cause life-threatening hypoglycemia or hyperglycemia. Always work with your diabetes care team to determine appropriate insulin regimens and dosing strategies.

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