For an adult patient without severe insulin resistance or diabetes, how many units of regular insulin should be added to a TPN bag containing 180 g of dextrose using the rule of 1 unit per 10 g carbohydrate?

Insulin Dosing for TPN with 180g Dextrose

Add 18 units of regular human insulin directly to the TPN bag containing 180g of dextrose, using the standard 1 unit per 10g carbohydrate ratio. 1

Initial Insulin Calculation

• The American College of Clinical Endocrinologists recommends starting with 1 unit of regular insulin per 10g of carbohydrate in TPN, which yields 18 units for 180g dextrose (180g ÷ 10 = 18 units). 1

• Regular insulin is the only appropriate formulation to add directly to TPN solutions due to its compatibility with parenteral nutrition components. 1

• This 1:10 ratio serves as the standard starting point for patients without severe insulin resistance or diabetes. 1

Monitoring Protocol

• Check blood glucose every 6 hours initially after starting the TPN with insulin. 1

• Target blood glucose between 140-180 mg/dL during TPN therapy. 1

• If the patient requires more than 20 units of subcutaneous correctional insulin in any 24-hour period, increase the insulin dose in the next TPN bag. 1

Correctional Insulin Coverage

• Provide subcutaneous regular insulin every 6 hours (or rapid-acting insulin every 4 hours) as correctional doses for hyperglycemia beyond the basal TPN insulin. 1

• The scheduled insulin in the TPN bag provides baseline coverage; correctional insulin addresses glucose excursions. 1

Daily Adjustment Strategy

• Increase the TPN insulin dose daily based on the previous 24-hour glucose pattern and total correctional insulin used. 1

• If average glucose remains ≥180 mg/dL or correctional insulin exceeds 20 units per day, add those correctional units to the next TPN bag's insulin dose. 1

Critical Safety Measures

• If TPN is unexpectedly interrupted, immediately start 10% dextrose infusion at 50 mL/hour to prevent hypoglycemia, since the regular insulin in the TPN continues to exert its effect. 1

• The maximum safe glucose infusion rate is 5 mg/kg/min; for a 70 kg patient, 180g over 24 hours equals approximately 2.9 mg/kg/min, well within safe limits. 2, 1

Common Pitfalls to Avoid

• Do not use rapid-acting or long-acting insulin analogs in TPN bags—only regular human insulin is compatible with parenteral nutrition solutions. 1

• Do not rely solely on sliding-scale correctional insulin without scheduled insulin in the TPN—this approach fails to provide adequate baseline coverage and results in persistent hyperglycemia. 1

• Do not forget to continue basal insulin if the patient has type 1 diabetes, even when TPN provides nutritional insulin coverage, to prevent diabetic ketoacidosis. 1

• Patients with type 2 diabetes, obesity, or critical illness typically require higher insulin doses than the 1:10 starting ratio due to insulin resistance, so expect to titrate upward within 24-48 hours. 1