Why is blood glucose management important before surgery?

It is always important to manage your blood glucose, but it is especially important to have good glucose control before surgery. Managing your blood glucose effectively before surgery helps reduce your risk of infection and other potential problems after surgery.

How does surgery affect my blood glucose levels?

Stress before, during, and after surgery can cause your body to release hormones and other inflammatory substances that can cause your blood glucose levels to change. Other changes related to surgery, such as alterations in diet and medication routine can also make it harder to manage your blood glucose levels

What are the general goals of diabetes management before surgery?

  • Avoidance of hypoglycemia (low blood sugar) and hyperglycemia (elevated blood sugar)
  • Prevention of ketoacidosis/hyperosmolar states (diabetic emergencies)
  • Maintenance of hydration and electrolyte balance

What are the factors that influence the management of diabetes before surgery?

  • Type of diabetes (Type 1 or 2)
  • Presence or absence of long-term complications of diabetes mellitus like kidney disease, coronary heart disease, peripheral vascular disease, or hypertension
  • Baseline glycemic control (HbA1c level)
  • Presence or absence of hypoglycemia including frequency, awareness, and severity
  • Current pharmacologic therapy, including type of medication (insulin or oral agents), dosing, and specific timing
  • Characteristics of surgery like when the patient must stop eating prior to surgery, type of surgery (major or minor), timing of the operative procedure, and duration of the procedure
  • Type of anesthetic (epidural or regional versus general anesthesia)

What should I do before I schedule my surgery?

Before you schedule the surgery, make an appointment with the doctor who manages your diabetes for a comprehensive checkup. Review your self-management guidelines and ask your doctor about the best way to manage diabetes before surgery. Your doctor may request additional tests during this visit in preparation for the surgery.

Ask your doctor how you should adjust your diabetes medications or insulin before surgery. 

Inform the person who schedules your surgery that you have diabetes and would like your surgery to be scheduled early in the morning (ideally before 9 AM). This causes the least amount of change to your insulin or diabetes medication schedule.

If you use an insulin pump and will have general anesthesia or a surgery that lasts longer than one hour, your insulin pump will likely need to be disconnected before surgery. Your doctors will switch you to an alternative form of insulin therapy and the pump needs to be stored in a safe location during this period. You will be reconnected when you are able to safely manage it on discharge.

The week before surgery

Carefully follow your diabetes treatment plan and test your blood glucose as directed by your doctor. Record the results and bring your blood glucose record with you when you come for surgery.

Your pre-meal blood glucose goal should be 80 to 130 mg/dl (4.4-7.2 mmol/L)* or _______________________________

Your bedtime blood glucose goal should be 100 to 140 mg/dl (5.6-7.8 mmol/L)* or ______________________________

*More or less stringent targets may be appropriate for select patients as advised by the doctor

What are the general guidelines for management of diabetes before surgery?

For patients with type 2 diabetes managed with diet alone, no changes are usually needed. Supplemental short-acting insulin may be given (typically every 4 - 6 hours) if glucose levels rise over the desired targets during or after surgery.

For patients with type 2 diabetes who take oral hypoglycemic drugs or noninsulin injectables (e.g. glucagon-like peptide-1 [GLP-1] analogs [like exenatide or liraglutide]), their anti-diabetic medications are usually stopped the morning of surgery. Supplemental short-acting insulin may be given (typically every 4 - 6 hours) if glucose levels rise over the desired targets during or after surgery. When you are able to eat again, your doctor may resume your prior home regimen or switch you to an alternative schedule of medications.

For patients with type 1 or type 2 diabetes who are treated with insulin, subcutaneous insulin can be continued before the operation at a reduced dose for procedures that are not long and complex (eg, no more than one or two missed meals). However, intravenous (IV) insulin may be required for long and complex procedures (like open heart surgery or kidney transplantation). When you are able to eat again, your doctor may resume your prior home regimen or switch you to an alternative schedule of medications.

What should I do if blood glucose is too low (less than 70 mg/dl or 3.8 mmol/l) the morning of surgery at home?

  • Take 120ml of regular soda/juice or three glucose tablets
  • Wait 15 minutes
  • Test your blood glucose again
  • If it’s still low, repeat as advised above
  • If your blood glucose stays low after two treatments, ask a family member or a friend to bring you to the hospital. Your surgery may need to be delayed or postponed.

What should I do if blood glucose is too high (more than 180 mg/dl or 10mmol/l) the morning of surgery at home?

If your blood glucose level is too high on the morning of surgery, ask a family member or a friend to bring you to the hospital.

Supplemental short-acting insulin may be given to bring your blood glucose level to target.

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