How do you calculate insulin doses?

Insulin Dose Calculation Guidelines

For patients requiring insulin therapy, calculate the initial insulin dose based on the patient's weight, with a starting dose of 0.2-0.4 units/kg/day total insulin, with approximately 50% as basal insulin. 1

Initial Insulin Dosing

Basal Insulin Calculation

• Start with basal insulin at 0.1-0.2 units/kg per day
• For a 70 kg patient, this would be 7-14 units of basal insulin daily
• Titrate by increasing 2 units every 3 days until reaching fasting glucose goals (80-130 mg/dL) without hypoglycemia 1
• For elderly patients or those with comorbidities, start at the lower end (0.1 units/kg) and titrate more cautiously 1

Prandial (Mealtime) Insulin Calculation

• For patients requiring prandial insulin, start with 4 units or 10% of the basal insulin dose at the largest meal or meal with greatest postprandial excursion 2
• Example: If basal insulin is 20 units, initial prandial dose would be 2-4 units
• Patients with type 2 diabetes typically require higher daily doses (approximately 1 unit/kg) compared to those with type 1 diabetes 2

Insulin Dose Adjustment

Basal Insulin Titration

• Adjust basal insulin dose every 3 days based on fasting glucose readings 1
• Increase dose by 2 units if fasting glucose remains above target (80-130 mg/dL) 1
• If fasting glucose is consistently <80 mg/dL or hypoglycemia occurs, reduce dose by 10-20% 1
• A basal dose exceeding ~0.5 units/kg/day may indicate need for prandial insulin 1

Prandial Insulin Titration

• Intensify prandial insulin regimen based on individual needs and postprandial glucose readings 2
• When adding significant prandial insulin doses, particularly with evening meals, consider decreasing basal insulin to prevent nocturnal hypoglycemia 2

Correction (Supplemental) Insulin

• Use the following correction doses of rapid-acting insulin for blood glucose >180 mg/dL: 1
  • 150-200 mg/dL: Add 2 units rapid-acting insulin
  • 201-250 mg/dL: Add 4 units rapid-acting insulin
  • 251-300 mg/dL: Add 6 units rapid-acting insulin

  • 300 mg/dL: Add 8 units and notify provider

Special Insulin Regimens

Basal-Bolus Regimen

• Total daily dose: 0.3-0.5 units/kg/day
• 50% as basal insulin (once daily)
• 50% as prandial insulin (divided between meals) 1
• Example for 80 kg patient: Total 32 units (16 units basal, 16 units divided as 5-5-6 units at meals)

Premixed Insulin Regimen

• When converting from basal insulin to 70/30 premixed insulin:
  • Calculate as 80% of current basal insulin dose
  • Divide as 2/3 before breakfast and 1/3 before dinner 1
• Example: If basal dose is 30 units, premixed dose would be 24 units total (16 units morning, 8 units evening)

Monitoring and Adjustments

• Monitor blood glucose with 4 or more tests daily, including fasting and postprandial measurements 1
• Titrate doses based on self-monitoring blood glucose levels
• For hypoglycemia, determine the cause and if no clear reason, lower the corresponding dose by 10-20% 1

Insulin Administration Technique

• Administer insulin subcutaneously using proper technique
• Use short needles (e.g., 4-mm pen needles) and rotate injection sites to avoid lipohypertrophy 3
• Do not reuse needles to prevent contamination and infection 3
• For insulin pens, perform a safety test before each injection to ensure proper function 3

Common Pitfalls to Avoid

• Underdosing insulin initially due to fear of hypoglycemia
• Failing to adjust basal and prandial components separately
• Not accounting for increased insulin requirements in patients with obesity or insulin resistance
• Forgetting to reduce insulin doses during periods of decreased caloric intake
• Not coordinating insulin administration with meal timing, particularly in hospital settings 2

By following these guidelines for insulin dose calculation and adjustment, you can optimize glycemic control while minimizing the risk of hypoglycemia in patients requiring insulin therapy.