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Insulin Dosage Calculator

Calculate mealtime insulin correction doses based on current blood sugar, target blood sugar, and insulin sensitivity factor. For educational reference on insulin dose adjustments.

Reviewed by Chase FloiedUpdated

This free online insulin dosage calculator provides instant results with no signup required. All calculations run directly in your browser — your data is never sent to a server. Enter your values below and see results update in real time as you type. Perfect for everyday calculations, homework, or professional use.

How much 1 unit of rapid insulin lowers BG

Grams of carb covered by 1 unit

How to Use This Calculator

1

Enter your input values

Fill in all required input fields for the Insulin Dosage Calculator. Most fields include unit selectors so you can work in your preferred unit system — metric or imperial, whichever matches your problem.

2

Review your inputs

Double-check that all values are correct and that you have selected the right units for each field. Incorrect units are the most common source of calculation errors and can produce results that are off by factors of 2, 10, or more.

3

Read the results

The Insulin Dosage Calculator instantly computes the output and displays results with units clearly labeled. All calculations happen in your browser — no loading time and no data sent to a server.

4

Explore parameter sensitivity

Try adjusting individual input values to see how the output changes. This is a quick and effective way to develop intuition about how different parameters influence the result and to identify which inputs have the largest effect.

Formula Reference

Insulin Dosage Calculator Formula

See calculator inputs for the governing equation

Variables: All variables and their units are labeled in the calculator interface above. Input fields accept values in multiple unit systems — select your preferred unit from the dropdown next to each field.

When to Use This Calculator

  • •Use the Insulin Dosage Calculator for personal health tracking and wellness monitoring, establishing a baseline and tracking changes over time.
  • •Use it when recording fitness metrics to track progress toward health or athletic goals.
  • •Use it to compare measurements before and after a lifestyle, diet, or training change to quantify the impact.
  • •Use it as a conversation starter before a doctor's appointment, bringing objective data to discuss with a healthcare professional.

About This Calculator

The Insulin Dosage Calculator is a free health and wellness calculation tool designed for personal use and general informational purposes. Calculate mealtime insulin correction doses based on current blood sugar, target blood sugar, and insulin sensitivity factor. For educational reference on insulin dose adjustments. This calculator provides reference values based on established health screening formulas and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Results may vary based on individual factors not captured by the calculation. Consult a qualified healthcare provider for personalized health guidance. All calculations are performed locally in your browser — no personal health data is transmitted or stored.

About Insulin Dosage Calculator

The Insulin Dosage Calculator computes mealtime (bolus) insulin doses by combining a correction dose (to bring current blood sugar to target) with a carb coverage dose (to cover carbohydrates in the upcoming meal). This is the standard approach to intensive insulin therapy used by type 1 diabetics and many insulin-dependent type 2 diabetics. The two key individualized parameters are the Insulin Sensitivity Factor (ISF) — how much one unit of rapid insulin lowers blood glucose — and the Insulin-to-Carb Ratio (ICR) — how many grams of carbohydrate one unit of insulin covers. Both are determined through careful self-monitoring and adjusted by the patient's diabetes care team.

The Math Behind It

Intensive insulin therapy mimics normal pancreatic function by combining long-acting basal insulin (covering fasting glucose) with rapid-acting bolus insulin at meals (covering food and correcting hyperglycemia). **Correction dose**: When blood glucose is above target, additional insulin is needed. The ISF tells you how far 1 unit drops your blood sugar. Common ISF ranges: - Insulin-sensitive (type 1, lean): 50-100 mg/dL per unit - Average: 30-50 mg/dL per unit - Insulin-resistant (type 2, obese): 10-30 mg/dL per unit The '1800 Rule' estimates ISF: ISF ≈ 1800 / Total Daily Dose (TDD) of insulin. **Carb coverage**: The ICR determines mealtime insulin for carbohydrate intake. Common ICR ranges: - Insulin-sensitive: 15-20 g per unit - Average: 10-15 g per unit - Insulin-resistant: 3-8 g per unit The '500 Rule' estimates ICR: ICR ≈ 500 / TDD. **Total bolus = correction dose + carb dose**. If the result is negative (blood sugar below target with no carbs), no bolus is given and treatment for hypoglycemia may be needed. **Important considerations**: - Active insulin on board (IOB) from recent boluses should be subtracted to avoid stacking - ISF and ICR often vary by time of day (less sensitive in the morning due to cortisol) - Exercise, illness, and stress significantly alter insulin requirements - These calculations are starting points; individual adjustments are essential

Formula Reference

Correction Dose

Correction = (Current BG - Target BG) / ISF

Variables: ISF = insulin sensitivity factor (mg/dL drop per 1 unit)

Carb Dose

Carb Dose = Carbs (g) / ICR

Variables: ICR = insulin-to-carb ratio (g per 1 unit)

Worked Examples

Example 1: High BG Before Lunch

Current BG 250 mg/dL, target 120, ISF 50, eating 60g carbs, ICR 10

Step 1:Correction: (250-120) / 50 = 2.6 units
Step 2:Carb dose: 60 / 10 = 6.0 units
Step 3:Total: 2.6 + 6.0 = 8.6 units

Bolus 8.6 units (round to 8.5 or 9 units based on pen/pump increments).

Example 2: Correction Only (No Meal)

Current BG 200 mg/dL, target 120, ISF 40, no carbs

Step 1:Correction: (200-120) / 40 = 2.0 units
Step 2:Carb dose: 0 / 10 = 0 units
Step 3:Total: 2.0 units

Give 2 units correction insulin.

Common Mistakes & Tips

  • !Insulin stacking — giving correction doses too close together without accounting for active insulin on board (IOB). Rapid insulin peaks at 1-2 hours and lasts 3-5 hours.
  • !Using the same ISF and ICR all day. Many patients need different ratios for breakfast (higher insulin resistance due to cortisol) vs. dinner.
  • !Not adjusting for exercise. Physical activity can increase insulin sensitivity 2-3 fold for 24-48 hours, significantly lowering insulin requirements.
  • !Treating this calculator as a substitute for medical guidance. ISF and ICR must be established and adjusted by a healthcare team.

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Frequently Asked Questions

What is the 1800 Rule for ISF?

ISF ≈ 1800 / Total Daily Dose of insulin. For example, if you take 45 units of insulin per day total (basal + bolus), ISF ≈ 1800/45 = 40 mg/dL per unit. This is a starting estimate; fine-tuning requires blood sugar monitoring.

What is the 500 Rule for ICR?

ICR ≈ 500 / Total Daily Dose. Using the same 45-unit TDD example: ICR ≈ 500/45 = 11 g per unit. This means 1 unit covers approximately 11 grams of carbohydrate.

Can I use this for type 2 diabetes?

Yes, if you are on intensive insulin therapy (basal-bolus regimen). Many type 2 diabetics on insulin use correction and carb-counting dosing. However, type 2 patients tend to have lower ISF values (more insulin required per mg/dL correction) due to insulin resistance.