What is the appropriate starting dose of bedtime Lantus (insulin glargine) for a patient with an HbA1c of 6.5% and blood glucose levels ranging from 200 to 600 mg/dL?

Starting Dose of Bedtime Lantus for Severe Hyperglycemia

For a patient with blood glucose ranging 200-600 mg/dL (despite an HbA1c of 6.5%), start Lantus at 0.2 units/kg once daily at bedtime, which represents the upper end of the standard dosing range due to the severe hyperglycemia present. 1, 2, 3

Critical Context: The HbA1c-Glucose Discordance

The HbA1c of 6.5% is misleading in this clinical scenario and should not guide your dosing decision. Blood glucose levels of 200-600 mg/dL indicate severe, acute hyperglycemia that requires immediate and aggressive insulin therapy. 1, 2 This discordance suggests either:

• Recent onset of severe hyperglycemia (HbA1c hasn't caught up yet)
• Hemoglobin variant or condition affecting HbA1c accuracy
• Possible type 1 diabetes presentation

Base your insulin dosing on the actual blood glucose values, not the HbA1c in this case. 1, 2

Specific Starting Dose Algorithm

Standard Approach for Severe Hyperglycemia:

• Start at 0.2 units/kg/day (upper end of the 0.1-0.2 units/kg range) given the blood glucose levels reaching 600 mg/dL 1, 2, 3
• Alternative fixed dose: 10 units once daily, but this is likely insufficient given the severity of hyperglycemia 1, 3

For More Aggressive Control (if blood glucose consistently >300-350 mg/dL):

• Consider starting at 0.3-0.4 units/kg/day for patients with marked hyperglycemia 1, 2
• Strongly consider basal-bolus insulin immediately rather than basal insulin alone if blood glucose ≥300-350 mg/dL with symptomatic hyperglycemia 1, 2

Example Calculation:

For a 70 kg patient:

• Standard severe hyperglycemia dose: 0.2 units/kg × 70 kg = 14 units at bedtime
• More aggressive approach: 0.3 units/kg × 70 kg = 21 units at bedtime

Evidence-Based Titration Protocol

Increase the dose by 4 units every 3 days if fasting blood glucose remains ≥180 mg/dL 1, 2

• If fasting glucose 140-179 mg/dL: increase by 2 units every 3 days 1, 2
• Target fasting plasma glucose: 80-130 mg/dL 1, 2
• For hypoglycemia without clear cause: reduce dose by 10-20% immediately 1, 2

The American Diabetes Association guidelines support this aggressive titration schedule, with dose adjustments every 3 days rather than weekly intervals to achieve glycemic targets faster. 1, 2

Critical Threshold to Recognize

When basal insulin exceeds 0.5 units/kg/day and blood glucose remains elevated, add prandial insulin rather than continuing to escalate basal insulin alone. 1, 2 This prevents "overbasalization" which leads to:

• Hypoglycemia (especially nocturnal) 1, 2
• High glucose variability 1, 2
• Bedtime-to-morning glucose differential ≥50 mg/dL 2

Essential Concurrent Therapy

• Continue or initiate metformin unless contraindicated, as it remains the foundation of type 2 diabetes therapy even when starting insulin 1, 2
• Consider whether this patient actually has type 1 diabetes given the extreme glucose variability (200-600 mg/dL range), which would require immediate basal-bolus insulin therapy 1, 2

Monitoring Requirements

• Daily fasting blood glucose monitoring is mandatory during the titration phase 1, 2
• Reassess insulin dose every 3 days during active titration 1, 2
• Assess adequacy at every clinical visit, looking for signs of overbasalization 1, 2

Common Pitfalls to Avoid

• Do not use the fixed 10-unit starting dose for this patient—it is grossly insufficient given blood glucose reaching 600 mg/dL 1, 2
• Do not delay titration—waiting longer than 3 days between adjustments unnecessarily prolongs time to glycemic control 1, 2
• Do not continue escalating basal insulin beyond 0.5-1.0 units/kg/day without adding prandial insulin if postprandial hyperglycemia persists 1, 2
• Do not ignore the possibility of type 1 diabetes—glucose levels of 600 mg/dL with such variability warrant consideration of immediate basal-bolus therapy and possible endocrinology consultation 1, 2

Safety Considerations

• Prescribe glucagon for emergency hypoglycemia management 1, 4
• Provide comprehensive education on blood glucose monitoring, hypoglycemia recognition and treatment, insulin injection technique, and "sick day" management 1, 2
• The FDA label specifies that Lantus must be administered at the same time each day, subcutaneously into the abdomen, thigh, or deltoid, with rotation of injection sites 3