When should sliding scale insulin with regular insulin be dosed in a patient who is nil per os (NPO)?

Sliding Scale Insulin Administration for NPO Patients

For patients who are NPO (nil per os), regular insulin sliding scale should be administered every 4-6 hours to correct hyperglycemia, while maintaining a basal insulin regimen to prevent metabolic decompensation. 1

Recommended Approach for NPO Patients

Insulin Regimen Components

• Basal insulin: Continue basal insulin even when NPO to prevent metabolic decompensation
• Correctional insulin: Use regular insulin sliding scale every 4-6 hours

Specific Recommendations

1. Frequency of blood glucose monitoring:

   • Check blood glucose every 4-6 hours in NPO patients 1
   • More frequent monitoring (every 30 min to 2 hours) may be needed for patients on IV insulin

2. Insulin administration timing:

   • For NPO patients, administer regular insulin sliding scale every 4-6 hours 1
   • Do NOT use rapid-acting insulin (lispro, aspart, glulisine) for sliding scale in NPO patients as it has too short a duration of action for the 4-6 hour interval 1

3. Basal insulin adjustment:

   • Continue basal insulin at 60-80% of home dose for NPO patients 1
   • For patients transitioning from IV to subcutaneous insulin, give basal insulin 2-4 hours before discontinuing IV insulin 1

Evidence-Based Sliding Scale Protocol for NPO Patients

Regular Insulin Sliding Scale (example):

• Blood glucose 150-200 mg/dL: 2 units regular insulin
• Blood glucose 201-250 mg/dL: 4 units regular insulin
• Blood glucose 251-300 mg/dL: 6 units regular insulin
• Blood glucose 301-350 mg/dL: 8 units regular insulin
• Blood glucose 351-400 mg/dL: 10 units regular insulin
• Blood glucose >400 mg/dL: 12 units regular insulin and notify provider

Important Considerations

Avoid Common Pitfalls

• Do not use sliding scale insulin as the sole treatment for hyperglycemia in hospitalized patients with diabetes 1
• Do not use rapid-acting insulin for sliding scale in NPO patients as it has too short a duration of action for the 4-6 hour interval 1
• Do not omit basal insulin in NPO patients as this increases risk of diabetic ketoacidosis 1

Special Situations

• For patients with type 1 diabetes who are NPO, never discontinue basal insulin due to risk of diabetic ketoacidosis 1
• For patients transitioning from IV insulin to subcutaneous insulin, administer basal insulin 2-4 hours before discontinuing IV insulin to prevent rebound hyperglycemia 1, 2

Monitoring Recommendations

• Monitor for hypoglycemia (BG <70 mg/dL) every 4-6 hours 1
• Assess for symptoms of hyperglycemia despite being NPO
• Evaluate need for adjustment of sliding scale if consistently high or low readings

Evidence Quality and Considerations

Current guidelines strongly discourage the use of sliding scale insulin as the sole treatment for hyperglycemia in hospitalized patients 1. However, when used as part of a comprehensive regimen that includes basal insulin, sliding scale insulin with regular insulin (not rapid-acting) every 4-6 hours is appropriate for NPO patients 1.

Research shows that patients receiving ≤50% of their home basal insulin dose while NPO had significantly more hyperglycemic events compared to those receiving >50% 3, supporting the recommendation to maintain basal insulin at 60-80% of the home dose for NPO patients.