On a cycled tube feed (TF) providing 116 g of carbohydrate (Cho), the patient receives 18 U of NPH insulin (NPH) and has blood glucose (BG) readings of 208, 286, and 259 mg/dL; what should the new NPH insulin dose be?

NPH Insulin Dose Adjustment for Cycled Tube Feeding with Persistent Hyperglycemia

Increase the NPH insulin dose to approximately 27–30 units to achieve better glycemic control, as the current 18 units is clearly insufficient given blood glucose readings consistently above 200 mg/dL.

Calculating the Required NPH Dose

For continuous or cycled tube feedings providing 116 g of carbohydrate, the recommended insulin dose is 1 unit per 10–15 g of carbohydrate per day 1. Using this guideline:

• Lower end calculation: 116 g ÷ 15 = 7.7 units (minimum)
• Upper end calculation: 116 g ÷ 10 = 11.6 units (maximum)
• Standard starting range: 8–12 units for nutritional coverage

However, the patient's current blood glucose readings of 208/286/259 mg/dL indicate severe inadequacy of the 18-unit dose 1. The current regimen is failing to achieve target glucose levels of 140–180 mg/dL for non-critically ill hospitalized patients 1.

Recommended Dose Adjustment Algorithm

Increase NPH insulin by 50% (from 18 to 27 units) as an initial adjustment 1. This approach is justified because:

• Blood glucose values are consistently ≥180 mg/dL, which warrants aggressive titration 1
• The patient requires approximately 1 unit per 4–5 g of carbohydrate based on current hyperglycemia, rather than the standard 1:10–15 ratio 1
• For tube-fed patients with persistent hyperglycemia, insulin requirements often exceed standard calculations due to insulin resistance, stress, or illness 1

NPH Administration Schedule for Cycled Tube Feeding

Administer NPH insulin twice daily (every 12 hours) to provide optimal coverage 1:

• Morning dose: 18 units (2/3 of total daily dose)
• Evening dose: 9 units (1/3 of total daily dose)
• Total daily dose: 27 units

Alternatively, NPH can be given three times daily (every 8 hours) at 9 units per dose if the cycled feeding runs continuously during waking hours 1, 2. Recent evidence suggests no significant difference in glycemic control between 8-hour and 12-hour NPH dosing intervals for tube-fed patients, though the 8-hour regimen requires more total insulin 2.

Concurrent Correctional Insulin Protocol

Add correctional insulin using regular human insulin subcutaneously every 6 hours (or rapid-acting insulin every 4 hours) in addition to scheduled NPH 1:

• For glucose >250 mg/dL: Give 2 units of regular insulin 1
• For glucose >350 mg/dL: Give 4 units of regular insulin 1

Never rely solely on correctional insulin—scheduled NPH must be the foundation 1.

Titration Protocol After Initial Adjustment

Monitor blood glucose every 4–6 hours and adjust NPH dose every 3 days based on patterns 1:

• If average glucose remains ≥180 mg/dL: Increase total daily NPH by 4 units every 3 days 1
• If average glucose is 140–179 mg/dL: Increase total daily NPH by 2 units every 3 days 1
• Target glucose range: 140–180 mg/dL for hospitalized patients 1

Critical Safety Considerations

If tube feeding is interrupted, immediately start 10% dextrose infusion at 50 mL/hour to prevent severe hypoglycemia 1, 3. This is essential because NPH insulin will continue to act even without carbohydrate intake.

For patients with type 1 diabetes receiving tube feeding, continue basal insulin even if feedings are discontinued to prevent diabetic ketoacidosis 1.

Evidence Supporting NPH Over Rapid-Acting Insulin for Tube Feeding

NPH insulin provides superior glycemic control compared to rapid-acting insulin analogs (aspart) for continuous tube feeding 4. A study demonstrated that sliding-scale NPH resulted in lower mean blood glucose and more patients achieving target ranges compared to insulin aspart in continuously tube-fed patients 4.

However, recent evidence suggests regular insulin may be superior to NPH for continuous enteral feeding, with significantly lower glucose levels and fewer days of hyperglycemia 5. Consider switching to regular insulin every 6 hours if NPH fails to achieve adequate control after appropriate dose escalation 5.

Common Pitfalls to Avoid

• Do not continue the current 18-unit dose when glucose readings are consistently >200 mg/dL—this represents therapeutic inertia and prolongs harmful hyperglycemia 1
• Do not use sliding-scale insulin as monotherapy—only 38% of patients achieve adequate control with this approach versus 68% with scheduled insulin 1
• Do not delay insulin adjustments—75% of hospitalized patients who experience hypoglycemia had no insulin dose adjustment before the next administration, highlighting the danger of under-adjusting 1
• Do not forget to coordinate insulin timing with tube feeding schedules—misalignment creates dangerous glycemic excursions 3, 6