Diabetes · Insulin
Insulin on the Morning of Surgery
Insulin is handled very differently from diabetes tablets — and each type of insulin has its own rule. Tick what you use to see the usual advice, then confirm your exact doses with your pre-op team.
New to this? Read why insulin is adjusted, not stopped first.
⚠️ If you have type 1 diabetes
You always need some background (basal) insulin — even while fasting. Never stop all your insulin. Stopping it can cause a dangerous condition called DKA. Your team reduces doses; they do not remove them all.
Frequently asked questions
Do I take my insulin on the morning of surgery?
It depends on the type. Long-acting (basal) insulin like Lantus, Levemir, Tresiba or Toujeo is usually taken at a reduced dose (many teams advise about 80% of normal). Mealtime (rapid/short) insulin is normally skipped while you are fasting, because there is no food to cover. Premixed insulin is often halved on the morning. Always follow the exact plan your pre-op team gives you.
I have type 1 diabetes — can I stop my insulin before surgery?
No. If you have type 1 diabetes you always need some background (basal) insulin, even when fasting. Stopping all of your insulin can cause diabetic ketoacidosis (DKA), which is dangerous. Your team will usually reduce your long-acting dose and may put you on an insulin drip — but you should never simply omit all insulin.
Why do I skip my mealtime insulin but not my long-acting?
Mealtime (rapid or short-acting) insulin is matched to food. While you are fasting there is no meal to cover, so taking it could drop your blood sugar too low. Long-acting (basal) insulin covers your background needs around the clock, so it is reduced rather than stopped — especially in type 1 diabetes.
I wear an insulin pump — what do I do for surgery?
Do not switch your pump off. Pumps usually keep running at the basal rate. Tell the hospital you wear a pump as early as possible — many have a pump policy and may switch you to an insulin drip for longer operations. Bring spare supplies, a charged device and your settings.
What is a sliding scale or insulin drip?
For longer surgery, fasting for a long time, or if your sugars are hard to control, the team may run a variable-rate insulin infusion (VRIII) — sometimes called a sliding scale or insulin drip. It gives insulin and glucose through a vein and is adjusted to your blood sugar, so you do not have to manage doses yourself during the operation.