How to calculate insulin dose for type 1 Diabetes

To calculate an insulin dose for someone with Type 1 Diabetes, one must understand individual needs. It is essential to tailor the dose to manage blood sugar effectively.

The process typically includes calculating basal insulin, bolus insulin, and adjustments for meals and corrections.

Basal Insulin (Long-Acting Insulin)

Maintains steady blood sugar levels between meals and overnight.

• Initial Dose Calculation
  • Daily Insulin Requirement:
    • Typically 0.4–1.0 units per kilogram of body weight per day.
    • Example: A 70 kg individual might need 28–70 units/day.
  • Basal Insulin Dose: Usually 50% of the total daily dose (TDD).
    • Example: For a TDD of 40 units, basal insulin would be 20 units.

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Bolus Insulin (Rapid-Acting Insulin for Meals)

Bolus Insulin Covers blood sugar spikes caused by meals.

• Carbohydrate Ratio: Determines how much insulin is needed for the carbohydrates consumed.
  • General Rule: 500 ÷ TDD = grams of carbohydrates covered by 1 unit of insulin.
  • Example: For a TDD of 40 units, 1 unit covers 12.5 grams of carbohydrates.
• Calculating Meal Dose:
  • Divide total grams of carbohydrates in the meal by the carbohydrate ratio.
  • Example: If eating 50 grams of carbs and the ratio is 1:12.5, the dose is 4 units.

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Correction Factor (Insulin Sensitivity Factor)

Insulin Sensitivity Factor Lowers high blood sugar to target levels.

• Rule of 1800: Used for rapid-acting insulin.
  • 1800 ÷ TDD = mg/dL blood sugar lowered by 1 unit of insulin.
  • Example: For a TDD of 40 units, 1 unit lowers blood sugar by 45 mg/dL.
• Correction Dose:
  • (Current Blood Sugar – Target Blood Sugar) ÷ Correction Factor = Units of insulin needed.
  • Example: If current blood sugar is 200 mg/dL, the target is 120 mg/dL, and the correction factor is 45:
    • (200 – 120) ÷ 45 = 1.78 ≈ 2 units.

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Key points about insulin dose for type 1 Diabetes

• Physical activity can reduce insulin needs; adjust doses appropriately.
• These can increase insulin requirements.
• Use a continuous glucose tracker (CGM) or frequent testing to track blood sugar.

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Example: Daily Dose Calculation for type 1 diabetes

1. Basal Insulin: 20 units/day.
2. Bolus Insulin:
   • Breakfast: 30 grams carbs ÷ 12.5 = 2.4 ≈ 2 units.
   • Lunch: 40 grams carbs ÷ 12.5 = 3.2 ≈ 3 units.
   • Dinner: 50 grams carbs ÷ 12.5 = 4 ≈ 4 units.
3. Correction:
   • If pre-meal blood sugar is 200 mg/dL and target is 120 mg/dL: 2 units.
   Total Insulin: 31 units/day (20 basal + 11 bolus).