How should rapid-acting insulin (e.g. Novolog (insulin aspart) or Humalog (insulin lispro)) be managed in a diabetic patient who is nothing by mouth (NPO)?

Management of Rapid-Acting Insulin in NPO Diabetic Patients

For diabetic patients who are NPO, basal insulin or a basal-plus-bolus correction regimen should be continued, while scheduled prandial rapid-acting insulin should be held and replaced with correction-dose rapid-acting insulin administered every 4-6 hours as needed based on blood glucose monitoring. 1, 2

Core Management Strategy

Basal Insulin Management

• Continue basal insulin (glargine, detemir, or NPH) at the patient's usual dose or slightly reduced to maintain baseline glucose control, as the body has ongoing basal insulin requirements even when fasting 1, 3
• "Hold-the-insulin" routines are dangerous and should never be implemented for NPO patients 3
• Basal insulin prevents hyperglycemia and ketosis during fasting states 1

Rapid-Acting Insulin Management

• Hold all scheduled prandial doses of rapid-acting insulin (Novolog/aspart or Humalog/lispro) since the patient is not eating 1
• Administer rapid-acting insulin every 4-6 hours as correction doses only, based on point-of-care glucose monitoring 1, 2
• For adult patients, a typical correction scale is 5-unit increments for every 50 mg/dL increase in blood glucose above 150 mg/dL, up to 20 units for blood glucose of 300 mg/dL 1

Specific Correction Insulin Dosing Protocol

The following correction scale can be used for NPO patients (adjust based on insulin sensitivity) 2:

• Blood glucose <100 mg/dL (5.5 mmol/L): No correction insulin 2
• Blood glucose 100-150 mg/dL (5.5-8.3 mmol/L): 2 units rapid-acting insulin 2
• Blood glucose 151-200 mg/dL (8.4-11.1 mmol/L): 4 units rapid-acting insulin 2
• Blood glucose 201-250 mg/dL (11.2-13.9 mmol/L): 6 units rapid-acting insulin 2
• Blood glucose 251-300 mg/dL (14.0-16.7 mmol/L): 8 units rapid-acting insulin 2
• Blood glucose 301-350 mg/dL (16.8-19.4 mmol/L): 10 units rapid-acting insulin 2
• Blood glucose >350 mg/dL (>19.4 mmol/L): 12 units rapid-acting insulin and contact physician 2

Dose Adjustments Based on Insulin Sensitivity

• Insulin-sensitive patients: Reduce correction doses by 50% 2
• Insulin-resistant patients: Increase correction doses by 50-100% 2

Monitoring Requirements

• Perform point-of-care glucose testing every 4-6 hours for NPO patients on subcutaneous insulin 1, 2
• More frequent monitoring (every 2-4 hours) may be needed if glucose is unstable 1
• Document all hypoglycemic episodes (glucose <70 mg/dL) and adjust the regimen accordingly 1

Critical Pitfalls to Avoid

The Sliding Scale Trap

• Never use sliding scale insulin as the sole treatment for hospitalized diabetic patients, even when NPO 1
• Sliding scale insulin without basal insulin is associated with suboptimal glycemic control and increased complications 1, 2
• The correction insulin described above must be used in addition to basal insulin, not as a replacement 2

Hypoglycemia Prevention

• Avoid administering rapid-acting insulin at bedtime to prevent nocturnal hypoglycemia 2
• The basal-bolus approach carries a 4-6 times higher risk of hypoglycemia compared to simple correction scales, requiring vigilant monitoring 2
• Have a standardized hypoglycemia management protocol in place 1

Transition Planning

When DKA is Resolved but Patient Remains NPO

• Continue intravenous insulin infusion if the patient was in DKA 1
• Supplement with subcutaneous regular insulin every 4 hours as needed for correction 1
• Maintain fluid replacement 1

When Transitioning from IV to Subcutaneous Insulin

• Administer subcutaneous basal insulin 2-4 hours before discontinuing IV insulin to prevent rebound hyperglycemia 1
• Convert to basal insulin at 60-80% of the total daily IV infusion dose 1

When Patient Resumes Eating

• Resume scheduled prandial rapid-acting insulin immediately before meals (within 15 minutes) 4, 5
• Continue basal insulin as the foundation of therapy 1
• Adjust prandial doses based on carbohydrate intake if oral intake is poor 1

Special Considerations

Type 1 Diabetes Patients

• Never completely discontinue insulin in type 1 diabetes patients, even when NPO, as they have absolute insulin deficiency and risk developing DKA 5, 3
• Basal insulin requirements persist regardless of oral intake 3

Pharmacokinetic Advantages of Rapid-Acting Analogs

• Insulin aspart (Novolog) and insulin lispro (Humalog) have nearly identical profiles with onset of action at 5 minutes, peak at 1-2 hours, and duration of 3-4 hours 4, 6, 7
• These rapid kinetics make them ideal for correction dosing in NPO patients, as they act quickly and clear faster than regular insulin 6, 7
• Lower risk of delayed hypoglycemia compared to regular insulin 6, 7