What is the starting dose of insulin for a patient with obesity (body mass index >30) and newly diagnosed diabetes?

Starting Insulin Dose for a 323-Pound Patient

For a 323-pound (147 kg) patient with newly diagnosed type 2 diabetes and obesity, start with basal insulin at 15-29 units once daily (0.1-0.2 units/kg/day), administered at the same time each day, with aggressive titration by 2-4 units every 3 days until fasting glucose reaches 80-130 mg/dL. 1, 2

Initial Dose Calculation

• The American Diabetes Association recommends a starting dose of 0.1-0.2 units/kg/day for insulin-naive patients with type 2 diabetes 1, 2
• For this 323-pound (147 kg) patient, the calculation yields:
  • Lower range: 147 kg × 0.1 units/kg = 15 units once daily
  • Upper range: 147 kg × 0.2 units/kg = 29 units once daily 1, 2
• Alternatively, a flat starting dose of 10 units once daily is acceptable for patients with mild-to-moderate hyperglycemia 1, 2

When to Use Higher Starting Doses

• For patients with severe hyperglycemia (blood glucose ≥300-350 mg/dL, HbA1c ≥9%, or symptomatic/catabolic features), consider starting doses of 0.3-0.5 units/kg/day as total daily dose, split between basal and prandial insulin 2, 3
• This would translate to 44-74 units total daily dose for this patient, with approximately 50% given as basal insulin 2, 3
• Immediate basal-bolus therapy is recommended when HbA1c is 10-12% with symptomatic features 2, 3

Evidence-Based Titration Algorithm

• Increase basal insulin 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 is ≥180 mg/dL 1, 2
• Target fasting plasma glucose: 80-130 mg/dL 1, 2
• If hypoglycemia occurs without clear cause, reduce the dose by 10-20% immediately 1, 2

Foundation Therapy Considerations

• Continue metformin unless contraindicated, even when initiating insulin therapy, as it reduces total insulin requirements and provides complementary glucose-lowering effects 1, 2, 3
• Metformin should be titrated to at least 1000 mg twice daily (2000 mg total daily), with maximum effective doses up to 2500 mg/day 2

Critical Threshold: Recognizing Overbasalization

• When basal insulin exceeds 0.5 units/kg/day (approximately 74 units for this patient) and approaches 1.0 units/kg/day, add prandial insulin rather than continuing to escalate basal insulin alone 1, 2
• Clinical signals of overbasalization include:
  • Basal dose >0.5 units/kg/day
  • Bedtime-to-morning glucose differential ≥50 mg/dL
  • Hypoglycemia (aware or unaware)
  • High glucose variability 1, 2

Adding Prandial Insulin When Needed

• Start with 4 units of rapid-acting insulin before the largest meal, or use 10% of the current basal insulin dose 1, 2
• Prandial insulin should be titrated by 1-2 units or 10-15% every 3 days based on postprandial glucose readings 2
• Consider adding prandial insulin when basal insulin has been optimized (fasting glucose 80-130 mg/dL) but HbA1c remains above target after 3-6 months 2

Monitoring Requirements

• Daily fasting blood glucose monitoring is essential during the titration phase 1, 2
• Assess adequacy of insulin dose at every clinical visit, looking specifically for signs of overbasalization 2
• Reassess and modify therapy every 3-6 months to avoid therapeutic inertia 2

Common Pitfalls to Avoid

• Do not delay insulin initiation in patients not achieving glycemic goals with oral medications—this increases morbidity risk 2
• Do not continue to increase basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia, as this leads to suboptimal control and increased hypoglycemia risk 1, 2
• Never rely on correction insulin (sliding scale) alone without scheduled basal insulin—this approach is associated with poor glycemic control and increased complications 3
• Do not wait longer than 3 days between basal insulin adjustments in stable patients, as this unnecessarily prolongs time to achieve glycemic targets 2

Patient Education Essentials

• Teach proper insulin injection technique and site rotation (thigh, abdominal wall, or upper arm) 2, 4
• Educate on recognition and treatment of hypoglycemia 2, 3
• Provide self-monitoring of blood glucose training and "sick day" management rules 2
• Instruct on insulin storage and handling 2, 4
• Equip patients with self-titration algorithms based on self-monitoring of blood glucose to improve glycemic control 2, 5