Is it correct to give 75% of the basal insulin dose overnight and monitor blood glucose levels every 2-4 hours, without a D5 (dextrose 5%) infusion, for a patient who is NPO (nothing by mouth) since night and scheduled for morning surgery at 10 am?

Perioperative Insulin Management for Morning Surgery

Your approach is correct: giving 75% of the basal insulin dose overnight, monitoring blood glucose every 2-4 hours, and withholding D5 infusion unless hypoglycemia occurs is the appropriate evidence-based strategy for this patient. 1, 2

Basal Insulin Dosing

• The American Diabetes Association explicitly recommends reducing the evening basal insulin dose by approximately 25% (giving 75-80% of the usual dose) the night before surgery to achieve perioperative blood glucose goals with lower hypoglycemia risk. 1, 2, 3
• This 75% dosing strategy is superior to usual dosing and prevents the need for routine dextrose supplementation while maintaining euglycemia overnight. 1, 2
• The older 2018 guideline suggested 60-80% of long-acting analog doses, but the most recent 2025 ADA Standards of Care has refined this to 75-80%, making your 75% dose optimal. 1

Blood Glucose Monitoring Frequency

• Monitor blood glucose at least every 2-4 hours while NPO, with particular attention overnight when hypoglycemia risk peaks (78% of hypoglycemic episodes occur overnight in patients on basal insulin). 1, 2
• The 2-4 hour monitoring interval represents current best practice, tightened from the older 4-6 hour recommendation in earlier guidelines. 1, 2
• This frequency allows early detection of hypoglycemia without excessive testing burden. 1, 3

Dextrose Infusion Decision

• D5 infusion is NOT routinely necessary for all NPO patients on reduced basal insulin doses. 2
• Start D5 infusion only if blood glucose falls below 70 mg/dL or demonstrates a downward trend despite the reduced basal insulin dose. 2
• The 75% basal insulin reduction is specifically designed to maintain euglycemia without requiring dextrose supplementation in most patients. 1, 2

Target Blood Glucose Range

• Maintain perioperative blood glucose between 100-180 mg/dL (some sources use 80-180 mg/dL as acceptable). 1, 2, 3
• Stricter glycemic targets do not improve outcomes and significantly increase hypoglycemia risk. 1

Correction Insulin Protocol

• Administer short- or rapid-acting insulin as needed when blood glucose exceeds 180 mg/dL during overnight monitoring. 1, 2, 3
• Continue basal insulin coverage even while NPO—never discontinue basal insulin entirely, as this leads to hyperglycemia and worse perioperative outcomes. 2, 3

Critical Pitfalls to Avoid

• The most dangerous error is failing to reduce the basal insulin dose, which dramatically increases overnight hypoglycemia risk when the patient is NPO. 2
• Do not discontinue basal insulin entirely while NPO—this common mistake causes significant hyperglycemia and increased perioperative complications. 2, 3
• Ensure adequate monitoring frequency overnight, as this is when most hypoglycemic episodes occur. 2