In a healthy adult with type 1 diabetes undergoing outpatient oral surgery, should the long‑acting basal insulin (e.g., insulin glargine, insulin detemir, insulin degludec) be discontinued the night before the procedure?

Perioperative Management of Long-Acting Basal Insulin

Long-acting basal insulin should NOT be completely halted the night before surgery; instead, administer a reduced dose of 75-80% of the usual long-acting analog insulin (or 50% of NPH insulin) on the evening before or morning of surgery to prevent life-threatening ketoacidosis in type 1 diabetes while minimizing hypoglycemia risk. 1

Critical Distinction: Type 1 vs Type 2 Diabetes

The management differs fundamentally based on diabetes type, as patients with type 1 diabetes have absolute insulin deficiency and face immediate ketoacidosis risk without basal insulin coverage 2:

Type 1 Diabetes (Your Patient Population)

• Never completely discontinue basal insulin in type 1 diabetes, as this creates immediate risk of diabetic ketoacidosis even with modest hyperglycemia 3
• The American Diabetes Association specifically recommends giving 75-80% of the usual long-acting analog insulin dose (glargine, detemir, or degludec) the evening before surgery 1
• This 25% dose reduction (compared to usual dosing) is more likely to achieve perioperative blood glucose goals of 100-180 mg/dL with lower hypoglycemia risk 1
• For patients on NPH insulin specifically, give 50% of the usual dose due to its peak effect profile 1

Type 2 Diabetes

• Patients with type 2 diabetes on basal insulin can follow the same 75-80% dosing recommendation 1
• However, type 2 patients have residual endogenous insulin production, making complete omission less immediately dangerous (though still not recommended) 1

Physiologic Rationale

The reduced-dose approach balances two competing risks:

• Basal insulin is essential to restrain hepatic glucose release and prevent ketosis, particularly in type 1 diabetes where there is absolute insulin deficiency 2
• Long-acting analogs (glargine, detemir, degludec) have durations of action exceeding 24 hours with nearly peakless profiles, providing continuous coverage 2, 4
• Complete discontinuation leaves patients without basal coverage for 24-36 hours (depending on the analog), creating unacceptable ketoacidosis risk 2
• The 25% dose reduction accounts for reduced caloric intake during fasting while maintaining essential basal coverage 1

Perioperative Monitoring Protocol

Once the reduced basal insulin dose is administered:

• Monitor blood glucose every 2-4 hours while the patient is NPO (nothing by mouth) 1, 5
• Target blood glucose range: 100-180 mg/dL (5.6-10.0 mmol/L) perioperatively 1
• Administer short- or rapid-acting insulin as needed for correction of hyperglycemia 1
• Consider starting glucose infusion (typically 5% dextrose) if the patient is fasting and on insulin, stopping it if blood glucose exceeds 300 mg/dL (16.5 mmol/L) 1, 5

Additional Perioperative Medication Management

For your type 1 diabetes patient undergoing outpatient oral surgery:

• Hold all prandial (mealtime) insulin on the morning of surgery since the patient will be NPO 1
• If the patient uses an insulin pump, it can be continued with basal rate delivery for short outpatient procedures, with correction boluses given by subcutaneous injection rather than through the pump 1
• Do NOT use sliding scale insulin alone without scheduled basal insulin, as basal-bolus coverage improves outcomes compared to reactive correction-only insulin 1, 5

Common Pitfalls to Avoid

• Never completely discontinue basal insulin in type 1 diabetes—this is the most critical error, as ketoacidosis can develop rapidly even at modest glucose levels 3, 6
• Do not confuse the management of basal insulin with oral agents like metformin (which should be stopped the night before) or SGLT2 inhibitors (which require 3-4 days discontinuation) 1, 5
• Avoid using older NPH insulin if possible, as it has an early peak effect and relatively short duration of action, increasing nocturnal hypoglycemia risk; long-acting analogs (glargine, detemir, degludec) are preferred 2, 4
• Do not rely on CGM (continuous glucose monitoring) alone during surgery—use point-of-care capillary or venous blood glucose testing 1

Postoperative Resumption

• Resume full basal insulin doses immediately when the patient can eat, as any delay increases ketoacidosis risk in type 1 diabetes 6
• Continue the basal-bolus regimen (basal insulin plus mealtime rapid-acting insulin) at pre-hospitalization doses 1, 6
• For outpatient oral surgery with rapid return to oral intake, the patient can resume their usual insulin regimen as soon as they are eating normally 1, 6