What is the recommended way to start basal‑bolus insulin therapy in a 70‑kg adult with uncontrolled diabetes mellitus who is currently taking metformin, sulfonylureas, and meglitinides?

Initiating Basal-Bolus Insulin in Uncontrolled Type 2 Diabetes

For a 70-kg adult with uncontrolled type 2 diabetes currently on metformin, sulfonylureas, and meglitinides, immediately discontinue the sulfonylurea and meglitinide, continue metformin at maximum tolerated dose (up to 2000-2550 mg daily), and initiate basal-bolus insulin at a total daily dose of 0.3-0.5 units/kg/day (21-35 units/day), split 50% as basal insulin once daily and 50% as prandial insulin divided among three meals. 1

Immediate Medication Adjustments

• Discontinue sulfonylureas and meglitinides when starting basal-bolus insulin to prevent additive hypoglycemia risk 1, 2
• Continue metformin at maximum tolerated dose (1000 mg twice daily, up to 2000-2550 mg/day total) unless contraindicated, as this combination reduces total insulin requirements by 20-30% and provides superior glycemic control with less weight gain 1, 3

Initial Insulin Dosing Calculation

Total Daily Dose (TDD)

• Start with 0.3-0.5 units/kg/day for standard-risk patients with uncontrolled diabetes 1, 2
• For a 70-kg patient: 21-35 units/day total 1
• Use the lower end (0.3 units/kg = 21 units/day) if the patient is elderly (>65 years), has renal impairment, or poor oral intake 1, 2

Basal Insulin Component

• Give 50% of TDD as basal insulin (long-acting analog: glargine, detemir, or degludec) 1, 2
• For a 70-kg patient: 10-18 units once daily, typically at bedtime 1, 2
• Administer at the same time each day for consistency 1

Prandial Insulin Component

• Give 50% of TDD as rapid-acting insulin (lispro, aspart, or glulisine) divided among three meals 1, 2
• For a 70-kg patient: 3-6 units before each meal (breakfast, lunch, dinner) 1, 2
• Administer 0-15 minutes before meals for optimal postprandial control 1, 2

Titration Protocols

Basal Insulin Titration

• Fasting glucose 140-179 mg/dL: increase basal insulin by 2 units every 3 days 1, 2
• Fasting glucose ≥180 mg/dL: increase basal insulin by 4 units every 3 days 1, 2
• Target fasting glucose: 80-130 mg/dL 1, 2
• If hypoglycemia occurs without clear cause, reduce dose by 10-20% immediately 1, 2

Prandial Insulin Titration

• Increase each meal dose by 1-2 units (or 10-15%) every 3 days based on 2-hour postprandial glucose readings 1, 2
• Target postprandial glucose: <180 mg/dL 1, 2

Correction Insulin Protocol

• Add 2 units of rapid-acting insulin for pre-meal glucose >250 mg/dL 1
• Add 4 units of rapid-acting insulin for pre-meal glucose >350 mg/dL 1
• These correction doses are in addition to scheduled prandial doses 1

Critical Threshold: Avoiding Overbasalization

• Stop escalating basal insulin when dose exceeds 0.5 units/kg/day (35 units for a 70-kg patient) 1, 2
• At this threshold, add or intensify prandial insulin rather than continuing basal escalation 1, 2
• Clinical signs of overbasalization include: basal dose >0.5 units/kg/day, bedtime-to-morning glucose differential ≥50 mg/dL, hypoglycemia episodes, and high glucose variability 1

Monitoring Requirements

• Daily fasting blood glucose monitoring is essential during titration 1, 2
• Check pre-meal glucose before each meal to guide prandial insulin adjustments 1
• Check 2-hour postprandial glucose to assess adequacy of prandial coverage 1, 2
• Reassess every 3 days during active titration and every 3-6 months once stable 1

Expected Clinical Outcomes

• With properly implemented basal-bolus therapy, 68% of patients achieve mean glucose <140 mg/dL versus only 38% with sliding-scale insulin alone 1
• Expect HbA1c reduction of 2-3% from baseline over 3-6 months 1
• No increased hypoglycemia risk when basal-bolus regimens are correctly implemented versus inadequate sliding-scale approaches 1

Common Pitfalls to Avoid

• Never use sliding-scale insulin as monotherapy—it is condemned by all major diabetes guidelines and shown to be ineffective 1
• Never discontinue metformin when starting insulin unless contraindicated, as this leads to higher insulin requirements and more weight gain 1, 3
• Never delay insulin initiation in patients not achieving glycemic goals with oral medications, as this prolongs hyperglycemia exposure and increases complication risk 1
• Never continue escalating basal insulin beyond 0.5-1.0 units/kg/day without addressing postprandial hyperglycemia, as this causes overbasalization with increased hypoglycemia risk 1, 2
• Never give rapid-acting insulin at bedtime as a sole correction dose, as this markedly raises nocturnal hypoglycemia risk 1

Patient Education Essentials

• Insulin injection technique and site rotation to prevent lipohypertrophy 1
• Hypoglycemia recognition and treatment: treat any glucose <70 mg/dL immediately with 15 grams of fast-acting carbohydrate, recheck in 15 minutes, and repeat if needed 1
• Self-monitoring of blood glucose: at least four daily measurements (fasting, pre-meals, bedtime) during titration 1
• Sick-day management: continue insulin even if not eating, check glucose every 4 hours, maintain hydration 1
• Insulin storage and handling: store between 36-86°F, replace vials in use >1 month at room temperature 1