Calculating Total Daily Insulin Dose Based on Weight
For Type 2 diabetes patients initiating insulin therapy, start with 0.1-0.2 units/kg/day of basal insulin, while Type 1 diabetes patients require 0.4-1.0 units/kg/day total daily dose (with 0.5 units/kg/day being typical for metabolically stable patients), divided approximately 50% basal and 50% prandial. 1, 2
Type 2 Diabetes: Weight-Based Dosing
Initial Basal Insulin Dosing
- Standard initiation: 0.1-0.2 units/kg/day of basal insulin once daily 1, 2
- Alternative fixed dose: 10 units once daily for patients with mild-to-moderate hyperglycemia 1, 2
- Severe hyperglycemia (A1C ≥9%, blood glucose ≥300-350 mg/dL): Consider higher starting doses of 0.3-0.5 units/kg/day as total daily dose, using basal-bolus regimen from the outset 1, 2, 3
Titration Algorithm
- Increase by 2 units every 3 days if fasting glucose is 140-179 mg/dL 1, 2
- Increase by 4 units every 3 days if fasting glucose ≥180 mg/dL 1, 2
- Target fasting plasma glucose: 80-130 mg/dL 1, 2
Critical Threshold for Adding Prandial Insulin
- When basal insulin exceeds 0.5 units/kg/day, stop escalating basal insulin and add prandial coverage instead 1, 2
- Clinical signals of "overbasalization" include: basal dose >0.5 units/kg/day, bedtime-to-morning glucose differential ≥50 mg/dL, hypoglycemia, and high glucose variability 1, 2
Type 1 Diabetes: Weight-Based Dosing
Total Daily Dose Calculation
- Standard range: 0.4-1.0 units/kg/day total daily insulin 1, 2
- Typical starting dose for metabolically stable patients: 0.5 units/kg/day 1, 2
- Honeymoon phase: May require as low as 0.2-0.6 units/kg/day 2
- Higher requirements: During puberty, pregnancy, and medical illness, doses may exceed 1.0 units/kg/day 1, 2
Distribution Between Basal and Prandial
- 50% as basal insulin (long-acting analog) given once daily 1, 2
- 50% as prandial insulin (rapid-acting analog) divided among three meals 1, 2
- More precisely, 40-60% may be given as basal with 40-60% as prandial depending on individual patterns 2
Special Population Adjustments
Hospitalized Patients
- Insulin-naive or low-dose home insulin: Start with 0.3-0.5 units/kg/day total daily dose, divided 50% basal and 50% bolus 2, 4
- High-dose home insulin (≥0.6 units/kg/day): Reduce total daily dose by 20% upon admission to prevent hypoglycemia 2
- High-risk patients (elderly >65 years, renal failure, poor oral intake): Use lower doses of 0.1-0.25 units/kg/day 2
Renal Impairment
- CKD Stage 5 with Type 2 diabetes: Reduce total daily dose by 50% 2
- CKD Stage 5 with Type 1 diabetes: Reduce total daily dose by 35-40% 2
Patients on Steroids
- Add 0.1-0.3 units/kg/day of insulin glargine to usual regimen, with doses determined by steroid dose and oral intake 2
Practical Example Calculations
Type 2 Diabetes Patient (70 kg)
- Initial basal insulin: 7-14 units once daily (0.1-0.2 units/kg/day) 1, 2
- Severe hyperglycemia: 21-35 units total daily dose (0.3-0.5 units/kg/day), split 50% basal and 50% prandial 2, 3
Type 1 Diabetes Patient (70 kg)
- Total daily dose: 35 units (0.5 units/kg/day) 1, 2
- Basal insulin: 17.5 units once daily (50% of total) 1, 2
- Prandial insulin: 17.5 units divided among meals (approximately 6 units before each meal) 1, 2
Critical Pitfalls to Avoid
- Never delay insulin initiation in patients not achieving glycemic goals with oral medications, as this prolongs hyperglycemia exposure 2
- Never continue escalating basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia, as this leads to overbasalization with increased hypoglycemia risk 1, 2
- Never discontinue metformin when starting insulin unless contraindicated, as the combination provides superior control with less weight gain 1, 2
- Never use sliding scale insulin as monotherapy, as scheduled basal-bolus regimens provide superior glycemic control 2