What is the recommended reduction amount for long-acting insulin (e.g. glargine (Lantus))?

Adjusting Long-Acting Insulin Dosage

When reducing long-acting insulin (glargine/Lantus), decrease the dose by 2 units if experiencing hypoglycemia, or by 20% when switching from twice-daily dosing to once-daily dosing. 1

Systematic Approach to Long-Acting Insulin Adjustment

When to Reduce Long-Acting Insulin

1. Evidence of hypoglycemia:

   • If >2 fasting glucose values per week are <80 mg/dL (<4.4 mmol/L), reduce dose by 2 units 1
   • For severe or recurrent hypoglycemia, reduce dose regardless of A1C 1

2. When simplifying insulin regimens:

   • When converting from premixed insulin to basal-only: Use 70% of total daily dose as basal insulin 1
   • When switching from twice-daily to once-daily dosing: Reduce total dose by 20% 2
   • When changing from NPH to glargine: Reduce total daily dose by 20% 2

3. During special circumstances:

   • During fasting periods: Reduce dose by 25-35% if glucose levels are not well managed 1
   • For longer-acting analogs (glargine U-300 or degludec): Less dose reduction may be needed when switching timing 1

How to Adjust Long-Acting Insulin

• Titration algorithm:

  • Monitor fasting glucose values over 1 week
  • Target fasting glucose: 90-150 mg/dL (5.0-8.3 mmol/L) 1
  • If 50% of fasting values are above goal: Increase by 2 units
  • If >2 fasting values/week are <80 mg/dL: Decrease by 2 units 1

• Timing adjustments:

  • Consider changing from bedtime to morning administration 1
  • For patients with morning hyperglycemia despite bedtime administration, consider splitting the dose to twice daily 3

Special Considerations

Signs of Overbasalization

Watch for these indicators that basal insulin dose may be too high:

• High bedtime-to-morning glucose differential (>50 mg/dL)
• Frequent hypoglycemia (aware or unaware)
• High glucose variability 1

Switching Between Insulin Types

When switching between different basal insulins:

• Most can be converted unit-for-unit initially
• Reduce dose by 10-20% when switching from insulin detemir or U-300 glargine to another insulin 1
• Monitor closely and adjust based on glucose patterns

Combination Therapy Considerations

If basal insulin has been optimized but A1C remains above goal:

• Consider adding GLP-1 receptor agonist before adding prandial insulin 1
• For patients already on prandial insulin with doses >10 units/dose: Decrease prandial dose by 50% and add non-insulin agent 1

Practical Tips

• Do not use rapid- or short-acting insulin at bedtime 1
• Consider continuous glucose monitoring to identify overnight patterns 4
• For patients with persistent morning hyperglycemia, check blood glucose at bedtime, 3 AM, and upon waking to establish patterns 4
• When reducing insulin, prioritize avoiding hypoglycemia over perfect glycemic control, especially in older adults 1

Remember that insulin requirements may change with alterations in physical activity, diet, concurrent medications, and progression of diabetes. Regular monitoring and appropriate adjustments are essential for optimal glycemic control while minimizing hypoglycemia risk.