Perioperative Insulin Management
Insulin is NOT completely withheld before surgery—basal insulin is continued at reduced doses to prevent ketoacidosis, while prandial/bolus insulin is held. 1
Critical Principle: Never Allow Insulin Deficiency
- Patients on insulin therapy must receive basal insulin coverage at all times, as complete insulin withdrawal leads to ketoacidosis within hours, particularly in Type 1 diabetes. 2, 3
- The goal is to reduce insulin doses appropriately while maintaining baseline coverage, not to eliminate insulin entirely. 1
Evening Before Surgery
All insulin should be administered at usual doses the evening before surgery:
- Give the full usual dose of basal insulin (NPH, glargine, detemir, degludec) with the evening meal. 2
- Give the full usual dose of prandial/bolus insulin with the evening meal. 2
- Maintain insulin pumps at usual settings until arrival at the surgical unit. 2
- Consider reducing the evening basal dose by 25% to achieve better perioperative glucose control with lower hypoglycemia risk. 1
Morning of Surgery
Basal insulin is reduced but NOT withheld:
- NPH insulin: Give 50% of the usual morning dose. 1, 2, 4
- Long-acting analogs (glargine, detemir, degludec): Give 75-80% of the usual dose. 1, 4
- Ultra-long-acting insulin (Tresiba/degludec): No additional dose needed on the morning of surgery if given the previous evening, as it provides 24-hour coverage. 3
All prandial/bolus insulin is withheld:
- Hold all rapid-acting insulin (aspart, lispro, glulisine) on the morning of surgery. 2, 3
- Hold all short-acting regular insulin on the morning of surgery. 1
Intraoperative Management
- Monitor blood glucose at least every 2-4 hours while NPO. 1, 4
- Dose with short- or rapid-acting insulin as needed to maintain target range of 100-180 mg/dL. 1, 4
- For major surgery or poorly controlled diabetes, initiate IV insulin infusion at 1-2 units/hour with hourly glucose monitoring. 3, 5
Other Medications to Hold
- Metformin: Hold on the day of surgery to reduce lactic acidosis risk. 1, 2, 4
- SGLT2 inhibitors: Discontinue 3-4 days before surgery due to euglycemic ketoacidosis risk. 1, 4
- All other oral hypoglycemic agents: Hold the morning of surgery. 1, 2, 4
Target Glucose Range
- Perioperative blood glucose target: 100-180 mg/dL within 4 hours of surgery. 1, 4
- Tighter targets (80-180 mg/dL) do not improve outcomes and increase hypoglycemia risk. 1
- For elective surgeries, aim for A1C <8% whenever possible. 1, 4
Critical Pitfalls to Avoid
- Never completely withhold insulin in insulin-treated patients—this precipitates ketoacidosis. 2, 3
- Never use sliding scale insulin alone without basal insulin coverage—this leads to erratic glucose control. 3, 6
- Never resume metformin until confirming adequate renal function postoperatively and oral intake tolerance. 3
- Never fail to discontinue SGLT2 inhibitors 3-4 days preoperatively—this can cause euglycemic ketoacidosis. 4