How do I add long-acting insulin (e.g. Lantus (glargine)) to a regimen for a patient with uncontrolled diabetes mellitus?

Adding Long-Acting Insulin to a Regimen for Uncontrolled Diabetes

Start with 10 units of insulin glargine (Lantus) once daily at the same time each day, or use 0.1-0.2 units/kg body weight for patients with type 2 diabetes who have failed to achieve glycemic targets on oral medications. 1

Initial Dosing Strategy

For insulin-naive patients with type 2 diabetes:

• Begin with 10 units once daily OR 0.1-0.2 units/kg body weight, administered subcutaneously at the same time every day 1, 2
• Continue metformin unless contraindicated, and possibly one additional non-insulin agent 1
• Administer into the abdominal area, thigh, or deltoid, rotating injection sites to reduce lipodystrophy risk 2

For patients with severe hyperglycemia (A1C ≥9%, blood glucose ≥300-350 mg/dL, or symptomatic/catabolic features):

• Consider higher starting doses of 0.3-0.5 units/kg/day as total daily dose 1
• These patients may require immediate basal-bolus insulin rather than basal insulin alone 1

Systematic Titration Algorithm

Increase the basal insulin dose based on fasting glucose levels every 3 days: 1

• If fasting glucose is 140-179 mg/dL: increase by 2 units every 3 days 1
• If fasting glucose is ≥180 mg/dL: increase by 4 units every 3 days 1
• Target fasting plasma glucose: 80-130 mg/dL 1
• If hypoglycemia occurs, reduce the dose by 10-20% immediately 1

Daily fasting blood glucose monitoring is essential during the titration phase. 1

Critical Threshold: When to Stop Escalating Basal Insulin

When basal insulin exceeds 0.5 units/kg/day and approaches 1.0 units/kg/day, add prandial insulin rather than continuing to escalate basal insulin alone. 1 This prevents "overbasalization," a dangerous pattern where excessive basal insulin masks insufficient mealtime coverage. 1

Clinical signals of overbasalization include: 1

• Basal insulin dose >0.5 units/kg/day
• Bedtime-to-morning glucose differential ≥50 mg/dL
• Hypoglycemia episodes
• High glucose variability

Adding Prandial Insulin Coverage

If after 3-6 months of basal insulin optimization, fasting glucose reaches target but A1C remains above goal, add prandial insulin: 1

• Start with 4 units of rapid-acting insulin before the largest meal OR 10% of the current basal dose 1
• Titrate prandial insulin by 1-2 units or 10-15% every 3 days based on postprandial glucose readings 1
• Add prandial insulin before the meal causing the greatest glucose excursion 1

Administration Guidelines

Critical administration rules for insulin glargine: 3, 2

• Do NOT mix or dilute insulin glargine with any other insulin or solution due to its low pH 3, 2
• Administer at the same time each day for consistent coverage 2
• Use separate injections when combining with rapid-acting insulin 3

Common Pitfalls to Avoid

Do not delay insulin initiation in patients not achieving glycemic goals with oral medications—this causes harm through prolonged hyperglycemia exposure. 1

Do not continue escalating 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

Do not abruptly discontinue metformin when starting insulin therapy, as metformin combined with insulin reduces weight gain, lowers insulin requirements, and decreases hypoglycemia compared to insulin alone. 1, 4

Do not rely solely on correction insulin—scheduled insulin regimens with basal, prandial, and correction components are preferred. 1

Patient Education Requirements

Essential education components before discharge or initiation: 3

• Recognition and treatment of hypoglycemia
• Proper insulin injection technique and site rotation 1
• Self-monitoring of blood glucose 1
• "Sick day" management rules (continue diabetes medications, appropriate hydration, monitor glucose every 4 hours) 3
• Insulin storage and handling 1

Special Populations

For hospitalized patients who are insulin-naive or on low-dose insulin:

• Use a total daily dose of 0.3-0.5 units/kg, with half as basal insulin 1

For high-risk patients (elderly >65 years, renal failure, poor oral intake):

• Use lower doses of 0.1-0.25 units/kg/day to prevent hypoglycemia 1

For patients on high-dose home insulin (≥0.6 units/kg/day):

• Reduce the total daily dose by 20% upon hospitalization to prevent hypoglycemia 1