Target Preoperative Blood Glucose
The target preoperative blood glucose for diabetic patients undergoing surgery is 100-180 mg/dL (5.6-10.0 mmol/L), to be achieved within 4 hours of surgery. 1, 2, 3
Evidence-Based Target Range
The American Diabetes Association establishes this 100-180 mg/dL target based on evidence showing that stricter glycemic control (below 80-100 mg/dL) does not improve surgical outcomes and significantly increases hypoglycemia risk without clinical benefit. 1, 2 This represents a shift from older recommendations that suggested targets as low as 80 mg/dL, which have been abandoned due to harm from hypoglycemia. 1
Critically, do not pursue glucose targets below 100 mg/dL in the preoperative period—this increases hypoglycemia without improving outcomes. 2, 3
Preoperative Optimization Strategy
A1C Optimization
- Target A1C <8% (63.9 mmol/L) for elective surgeries whenever possible to reduce surgical risk, mortality, and infection rates. 1, 2
- Some institutions implement A1C cutoffs for elective procedures and run optimization programs to lower A1C before surgery. 1
Medication Management Before Surgery
SGLT2 Inhibitors (Critical):
- Must be discontinued 3-4 days before surgery to prevent life-threatening euglycemic diabetic ketoacidosis, which can occur even with normal glucose levels. 1, 2, 3
Day of Surgery:
- Hold metformin on the day of surgery. 1, 3
- Hold all other oral glucose-lowering agents the morning of surgery. 1, 3
Insulin Adjustments (Evening Before Surgery):
- Reduce basal insulin by 25% the evening before surgery—this approach achieves better perioperative glucose control with significantly lower hypoglycemia risk compared to usual dosing. 1, 2, 3
- Alternatively, give 50% of NPH dose or 75-80% of long-acting analog dose based on diabetes type and clinical judgment. 1, 3
Monitoring Protocol
- Monitor blood glucose at least every 2-4 hours while the patient is NPO (nothing by mouth). 1, 3
- Administer short- or rapid-acting insulin as needed to maintain the 100-180 mg/dL target range. 1, 3
Common Pitfalls to Avoid
Never pursue overly tight glucose control (<100 mg/dL) in the preoperative period, as perioperative glycemic targets stricter than 80-180 mg/dL have not shown improved outcomes and are associated with significantly more hypoglycemia. 1, 2, 3
Never continue SGLT2 inhibitors within 3-4 days of surgery—this poses a serious risk of euglycemic diabetic ketoacidosis, a life-threatening complication that can occur even when glucose levels appear normal. 2
Never fail to reduce insulin dosing the evening before surgery—using the usual full insulin dose increases hypoglycemia risk without benefit. 1, 2
Special Considerations
GLP-1 Receptor Agonists
There are limited data on the safe use and influence of GLP-1 receptor agonists on glycemia and delayed gastric emptying in the perioperative period, so exercise caution with these agents. 1, 3
Continuous Glucose Monitoring
CGM should not be used alone for glucose monitoring during surgery—traditional point-of-care testing remains the standard. 1, 3
High-Risk Patients
Perform a preoperative risk assessment for patients at high risk for ischemic heart disease and those with autonomic neuropathy or renal failure. 1