For a patient receiving 163 g of carbohydrate over 24 hours via tube feeding and using a 1‑unit‑per‑5‑gram carbohydrate‑to‑insulin ratio, what is the appropriate NPH (intermediate‑acting) insulin dose?

NPH Insulin Dosing for Tube Feeding with 163 g Carbohydrate Over 24 Hours

For a patient receiving 163 g of carbohydrate via tube feeding over 24 hours using a 1:5 carbohydrate‑to‑insulin ratio, the total daily NPH dose is approximately 33 units, divided as 16–17 units every 12 hours.

Dose Calculation

• The American Diabetes Association recommends 1 unit of insulin for every 10–15 g of carbohydrate delivered by continuous or cycled tube feeding 1, 2.
• Using the patient's specified 1:5 ratio (1 unit per 5 g carbohydrate), the calculation is: 163 g ÷ 5 = 32.6 units total daily dose 2, 3.
• Round to 33 units per day for practical administration 1, 2.

NPH Administration Schedule

• Administer NPH insulin twice daily (every 12 hours) to provide optimal basal coverage for continuous tube feeding 1, 2.
• Split the total dose: 16–17 units every 12 hours (e.g., 16 U at 8 AM and 17 U at 8 PM, or 17 U twice daily) 1, 2.
• NPH peaks 4–6 hours after administration, making twice‑daily dosing ideal for matching the continuous carbohydrate delivery 1, 4, 5.

Correction Insulin Protocol

• Add regular human insulin every 6 hours (or rapid‑acting insulin every 4 hours) as correction doses in addition to scheduled NPH 1, 2.
• Glucose >250 mg/dL: give 2 U regular insulin 1, 2.
• Glucose >350 mg/dL: give 4 U regular insulin 1, 2.
• Correction insulin must supplement—not replace—scheduled NPH; sliding‑scale monotherapy is condemned by major diabetes guidelines 1, 2.

Monitoring and Titration

• Check glucose every 4–6 hours during tube feeding 1, 2.
• Reassess the total NPH dose every 3 days based on average glucose trends 1, 2.
• Average glucose ≥180 mg/dL: increase total daily NPH by 4 U every 3 days 1, 2.
• Average glucose 140–179 mg/dL: increase total daily NPH by 2 U every 3 days 1, 2.
• Target glucose range: 140–180 mg/dL for non‑critically ill hospitalized patients 1, 2.

Critical Safety Considerations

• If tube feeding is interrupted, start a 10% dextrose infusion at 50 mL/h immediately to prevent severe hypoglycemia, because NPH insulin activity persists for 12–18 hours 1, 2.
• For patients with type 1 diabetes, continue basal insulin even when feedings stop to prevent diabetic ketoacidosis 1, 2.
• If any glucose reading falls <70 mg/dL, treat with 15 g fast‑acting carbohydrate (if feasible) and reduce the implicated NPH dose by 10–20% immediately 1, 2.

Common Pitfalls to Avoid

• Do not use the standard 1:10–15 ratio when the patient's established ratio is 1:5; this would result in severe under‑dosing (only 11–16 U/day instead of 33 U/day) 1, 2, 3.
• Avoid using sliding‑scale insulin as monotherapy; only ~38% achieve control versus ~68% with scheduled basal insulin 1, 2.
• Do not delay insulin adjustments; 75% of hospitalized patients who develop hypoglycemia had no dose change before the next administration 1, 2.
• Never discontinue NPH when tube feeding stops; switch to dextrose infusion instead to prevent hypoglycemia 1, 2.

Alternative Insulin Regimens (If NPH Unavailable)

• Regular insulin every 6 hours: Total 33 U ÷ 4 doses = 8–9 U every 6 hours 1, 2.
• Long‑acting basal insulin (glargine/detemir): Administer 50% of total dose (≈16 U) once daily plus correction insulin 1, 2.
• However, NPH every 12 hours remains the preferred regimen for continuous tube feeding because its pharmacokinetic profile better matches the continuous carbohydrate delivery 1, 2, 4, 5.