What Happens to Your Insulin Dose the Morning of Surgery

Preparing for surgery means adjusting your usual diabetes routine so that your blood sugar stays in a safe range while you’re fasting. One key change is how you handle your insulin dose the morning of surgery. Below is a clear guide based on current recommendations from diabetes and anesthesia experts. Always discuss any changes with your care team.

Why Adjustment Is Needed

• You can’t eat or drink before surgery, which raises the risk of low blood sugar (hypoglycemia).
• Stress hormones released during surgery can raise blood sugar (hyperglycemia).
• Anesthesia and IV fluids may alter insulin needs.
• Striking the right balance reduces risks like delayed wound healing, infection, or dangerous swings in blood sugar.

General Principles

1. Focus on preventing both high and low blood sugar.
2. Maintain some background (basal) insulin to avoid ketoacidosis in type 1 diabetes.
3. Avoid rapid‐acting (bolus) insulin when you’re not eating.
4. Customize based on your insulin regimen, type of diabetes, and surgery timing.

Day-Before Surgery

Your surgeon or anesthesiologist will give detailed instructions. Typical steps include:

• Continue your usual basal insulin (long-acting) dose the evening before.
• Skip or reduce extra injections of short-acting/meal-time insulin after your last meal, especially if dinner is early.
• Stop oral diabetes medications (metformin, sulfonylureas, SGLT2 inhibitors) as directed—often 24–48 hours before surgery.
• Check blood sugar more frequently (before meals, bedtime, overnight) to spot trends.

Insulin Dose the Morning of Surgery

On the day of surgery, you’ll usually be fasting. Here’s how most guidelines suggest adjusting your insulin:

Type 1 Diabetes

You must have some basal insulin on board to prevent ketoacidosis.

• Reduce your usual long-acting (basal) insulin by 20–50%.
• Do not take any rapid- or short-acting insulin if you’re not eating.
• Example: If your usual morning dose of glargine is 20 units, you might take 10–15 units instead.
• Monitor blood sugar on waking and before going to the hospital; treat any value under 90 mg/dL with a small, doctor-approved snack if permitted, or follow hypoglycemia protocols.

Type 2 Diabetes on Basal-Only Insulin

• Take 50–60% of your normal basal dose.
• Skip mealtime insulin altogether if you don’t plan to eat.
• Example: If you normally inject 30 units of detemir, take around 15–18 units.

Type 2 Diabetes on Basal–Bolus or Premixed Insulin

• Basal: Reduce by 20–50% (same as above).
• Bolus (rapid-acting or short-acting): Omit all morning bolus doses.
• If you use a premixed formula (e.g., 70/30), talk to your team. Many recommend taking only the basal portion or reducing the overall dose by 50%.

Insulin Pump Users

• Switch to your pump’s “surgery” or “suspend” feature if available.
• Lower your basal rate by 20–50% starting 1–2 hours before surgery.
• Suspend bolus features entirely.
• Check blood sugar frequently; have a protocol for treating low or high readings.

Managing Blood Sugar in the Hospital

• On arrival, hospital staff will measure your blood sugar. Keep your levels between 100–180 mg/dL (some teams aim tighter).
• IV glucose solutions may be started if you’re still fasting and your blood sugar dips.
• Your anesthesiologist or ward nurse will adjust insulin based on frequent checks—usually every 1–2 hours during longer surgeries.
• If you’re having same-day (outpatient) surgery, confirm how soon after you can resume eating and insulin.

Risks of Getting It Wrong

Hypoglycemia (low blood sugar):

• Symptoms: sweating, shakiness, confusion, irritability.
• Risks: seizure, loss of consciousness, delayed recovery.

Hyperglycemia (high blood sugar):

• Symptoms: thirst, frequent urination, nausea.
• Risks: dehydration, delayed wound healing, infection.

By planning your insulin dose the morning of surgery, you minimize both risks.

Tips for a Smooth Journey

• Confirm instructions in writing from your surgeon or diabetes team.
• Pack your usual glucose meter, test strips, and fast-acting carbs (glucose tablets).
• Wear medical ID indicating you have diabetes.
• Ask whether an insulin drip will replace your usual shots for long procedures.
• Arrange for close blood sugar monitoring post-op until you’re eating again.

Additional Support

If you notice symptoms like unusual dizziness, persistent high or low sugar levels, or any new concerns, it’s important to get guidance right away. You might consider doing a free, online symptom check, using the doctor approved Ubie Symptom Checker to help you decide if you need immediate care.

When to Speak to a Doctor

Never hesitate to speak to a doctor if you experience:

• Blood sugar below 70 mg/dL or above 300 mg/dL.
• Severe dizziness, confusion, or loss of consciousness.
• Signs of infection at any point (fever, redness, swelling).
• Anything you’re unsure about regarding your insulin dose the morning of surgery.

Your surgical and diabetes teams are there to help you through every step. Following these guidelines can keep you safer, more comfortable, and better positioned for a smooth recovery.