An adult with type 1 diabetes consumes 81 g of carbohydrate every 12 hours and uses an insulin‑to‑carbohydrate ratio of 1 unit per 5 g; what dose of NPH (intermediate‑acting) insulin should be prescribed for basal coverage?

NPH Insulin Dosing for Enteral Nutrition Coverage in Type 1 Diabetes

For an adult with type 1 diabetes receiving 81 g of carbohydrate every 12 hours via enteral feeding, start NPH insulin at 8–12 units every 12 hours (total 16–24 units/day), calculated as 1 unit per 10–15 g of carbohydrate in the formula, and continue basal insulin coverage even if feedings are interrupted. 1

Calculation Rationale

• 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.
• For 81 g of carbohydrate every 12 hours, the calculation yields 5–8 units per 12-hour period to cover the nutritional load alone 1.
• However, total insulin requirements include both nutritional coverage AND basal needs; the 1:10–15 g ratio addresses only the carbohydrate component 1.
• Most adults with type 1 diabetes require 0.4–1.0 units/kg/day total insulin, with approximately 40–50% allocated to basal coverage independent of feeding 1, 3.
• For a typical 70 kg adult, this translates to 14–35 units/day total, with 6–18 units/day as basal insulin 1, 3.

NPH Administration Schedule

• Administer NPH insulin every 12 hours (e.g., 8 AM and 8 PM) to provide optimal basal coverage for cycled tube feeding 1, 2.
• The twice-daily NPH regimen aligns with the 12-hour feeding cycle and provides continuous insulin action throughout the day 1.
• NPH peaks at 4–6 hours after administration, which helps control glucose during the active feeding period 1, 4.

Initial Dosing Strategy

• Start with 8 units NPH every 12 hours (16 units/day total) as a conservative initial dose for a patient with type 1 diabetes on enteral nutrition 1.
• This dose accounts for ≈6 units to cover 81 g carbohydrate (using 1:13.5 g ratio) plus ≈2 units for basal needs per 12-hour period 1.
• For patients with higher insulin resistance or those previously requiring >0.5 units/kg/day, consider starting at 10–12 units every 12 hours (20–24 units/day total) 1.

Concurrent Correctional Insulin Protocol

• Add regular human insulin every 6 hours (or rapid-acting analog every 4 hours) as correctional doses in addition to scheduled NPH 1.
• Glucose >250 mg/dL: give 2 units regular insulin 1, 2.
• Glucose >350 mg/dL: give 4 units regular insulin 1, 2.
• Scheduled NPH must remain the therapeutic foundation; correctional insulin alone is insufficient for patients with type 1 diabetes 1, 2.

Titration Protocol

• Monitor glucose every 4–6 hours and reassess the total NPH dose every 3 days based on the average glucose trend 1, 2.
• Average glucose ≥180 mg/dL: increase total daily NPH by 4 units every 3 days (2 units per dose) 1, 2.
• Average glucose 140–179 mg/dL: increase total daily NPH by 2 units every 3 days (1 unit per dose) 1, 2.
• Aim to maintain glucose 140–180 mg/dL as the target range for hospitalized patients 1, 2.

Critical Safety Considerations for Type 1 Diabetes

• If tube feeding is interrupted, start a 10% dextrose infusion at 50 mL/h immediately to avoid 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; this is an absolute requirement 1, 2.
• Never discontinue all insulin in type 1 diabetes, as complete cessation can precipitate DKA within hours 1.

Common Pitfalls to Avoid

• Do not use the 1:5 carb ratio (which would yield 16 units per 12 hours for carbohydrate coverage alone) without accounting for the patient's total insulin needs; this approach ignores basal requirements 1.
• Do not maintain inadequate NPH doses when glucose consistently exceeds 200 mg/dL; this represents therapeutic inertia and prolongs hyperglycemia 1, 2.
• 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.

Alternative Approach: Regular Insulin Every 6 Hours

• Instead of NPH every 12 hours, some specialists recommend regular insulin every 6 hours to cover continuous tube feeding 1.
• For 81 g carbohydrate over 12 hours (≈40.5 g per 6 hours), this would be 3–4 units regular insulin every 6 hours (12–16 units/day total) 1.
• This approach provides more frequent dosing adjustments but requires more injections 1.

Monitoring Requirements

• Check glucose every 4–6 hours during the initial titration phase 1, 2.
• Daily fasting glucose (if applicable) to assess basal adequacy 1.
• Adjust NPH doses every 3 days based on glucose patterns, not single readings 1, 2.