Medications
Insulin Before Surgery
Insulin is different from most drugs: you don't stop it, you adjust it. Getting this right keeps your sugar safe while you fast.
Quick answer
Why it matters
While you fast, you're not eating carbohydrates, so giving your full mealtime insulin would drop your blood sugar too low. That's why bolus doses are held.
But your body still needs some background insulin. In type 1 diabetes especially, stopping basal insulin entirely lets ketones build up and can cause diabetic ketoacidosis (DKA) — an emergency. So basal is reduced, not stopped.
Do not stop without instruction
What to ask your doctor
- Exactly how should I adjust my basal (long-acting) insulin the night before and morning of surgery?
- Should I hold my mealtime (short-acting) insulin while fasting?
- How often should I check my blood sugar, and what do I do for highs or lows?
- Should I bring my insulin and glucose meter to the hospital?
Red flags — call your team
Red flags — call your team
- Type 1 diabetes
- Blood sugar very high (with nausea/vomiting) or very low
- Ketones, deep breathing, or feeling very unwell
References
- Perioperative diabetes / insulin management guidance (specialty society consensus).
- American Society of Anesthesiologists (ASA). asahq.org
Frequently asked questions
Do I stop insulin before surgery?
No. You adjust it — usually reducing basal insulin and holding mealtime insulin while fasting. Get a specific plan from your team.
Can a type 1 diabetic stop insulin for surgery?
No. Type 1 diabetics must keep taking basal insulin (often at a reduced dose) — stopping it can cause DKA, a medical emergency.