What insulin dose adjustments are recommended for a patient taking long-acting (e.g. glargine) insulin in the morning who is scheduled for surgery?

Perioperative Management of Morning Long-Acting Insulin

For patients who take long-acting insulin (e.g., glargine) in the morning rather than evening, administer 75-80% of their usual dose on the morning of surgery. 1

Core Dosing Strategy

The American Diabetes Association guidelines explicitly recommend giving 75-80% of the usual long-acting analog insulin dose on the morning of surgery, regardless of whether the patient normally takes it in the morning or evening. 1

Key Differences from Evening Dosing

• Evening dosers should reduce their dose by 25% the night before surgery (giving 75% of usual dose), which has been shown to achieve better perioperative glucose control with lower hypoglycemia risk. 1, 2

• Morning dosers follow the same 75-80% reduction principle, but the dose is given on the morning of surgery itself rather than the night before. 1, 3

Perioperative Monitoring Requirements

• Monitor blood glucose every 2-4 hours while the patient is NPO (nothing by mouth). 1

• Target blood glucose range is 100-180 mg/dL within 4 hours of surgery. 1

• Administer short- or rapid-acting insulin as needed to maintain target range. 1

Evidence Supporting the 75-80% Dose

Research demonstrates that patients receiving 60-87% of their usual basal insulin dose (with optimal dosing around 75%) were most likely to achieve target blood glucose range with decreased hypoglycemia risk. 2 The mean and mode doses in the optimal group were 73% and 75% respectively, strongly supporting the guideline recommendation. 2

Critical Pitfalls to Avoid

• Never give the full usual dose on the morning of surgery, as this significantly increases hypoglycemia risk without improving outcomes. 2

• Never withhold basal insulin completely in surgical patients, as basal-bolus coverage (basal insulin plus premeal rapid-acting insulin) improves glycemic outcomes and reduces perioperative complications compared to correction-only insulin. 1

• Never pursue glucose targets stricter than 100-180 mg/dL perioperatively, as targets below 80-180 mg/dL do not improve outcomes and significantly increase hypoglycemia risk. 1, 4

Additional Perioperative Considerations

• Hold metformin on the day of surgery only. 1, 3

• Discontinue SGLT2 inhibitors 3-4 days before surgery to prevent euglycemic diabetic ketoacidosis. 1, 5, 3, 4

• Hold all other oral glucose-lowering agents on the morning of surgery. 1, 3