High Blood Sugar Levels After Surgery

How Diabetes and Blood Glucose Levels Can Affect Your Surgery Outcome

When you have surgery, the procedure itself and the effects of anesthesia put stress on the body that may result in elevated blood sugar (glucose) levels. Because of this, people with diabetes have an especially high risk for blood sugar complications following a surgical procedure. People who don't have diabetes or who have an undiagnosed case can also experience increased glucose levels post-surgery and the accompanying problems.

Doctor explaining test results to patient
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Whichever category you fall into, you can take appropriate steps to control your glucose levels before, during, and after surgery.

How Surgery Affects Blood Sugar

The stress of an operation, along with potential changes in lifestyle, diet, and exercise before and after surgery, can dramatically change your glucose levels. While everyone's at risk for high blood sugar levels after surgery, people with diabetes face even greater risks.

While the exact reason for this cannot always be determined, there are a few different factors that may be at play. The physical trauma associated with surgery can result in an increase in the stress hormone cortisol, along with catecholamines (neurotransmitters released into the bloodstream when you're stressed), both of which may result in increased insulin resistance—a lack of sensitivity to normal levels of insulin, requiring more and more insulin to remove glucose from the bloodstream.

Additionally, high levels of insulin often seen in diabetes can make arteries and veins less flexible, restricting blood flow that leads to slower healing times and poor circulation to the heart and other organs.

How Uncontrolled Levels Impact Surgery and Recovery

Blood sugar that's even slightly elevated can lead to delayed healing and increase your chances of getting a wound infection from less than 2% to almost 18%. In general, the higher the blood sugar, the higher these risks.

Additional risks include:

  • Slow or poor wound healing
  • Fluid and electrolyte imbalance
  • Kidney issues
  • Heart and/or lung problems
  • Neurological complications
  • Stroke
  • Post-surgical death

This increased risk is why the hospital may check your glucose frequently as you recover from surgery, whether you have diabetes or not.

Potential Complications and Solutions

Several complications may arise when you have diabetes and undergo surgery:

Glucose Fluctuations

If you have diabetes, make sure your healthcare provider has your blood sugar checked before meals and at bedtime while you're in the hospital. Checking your glucose during surgery is reasonable if the surgery is a lengthy one or if your glucose levels have been unpredictable.

Even those with diabetes who normally have well-controlled glucose levels thanks to diet and exercise can experience high levels of blood glucose during the hours and days following surgery. If your glucose is fluctuating widely between checks, you may even need to have it checked during the night if you're having symptoms of low or high blood glucose. An increase in your glucose values either before or after your surgery can be an indication of an infection.

If you are having same-day surgery, have your blood glucose level checked before you leave the facility. If you have diabetes, you may want to test more frequently once you're home until you are completely healed.

Medication Interactions

Be sure to let your surgeon know which medications you're currently taking or have recently taken.

Metformin, a common medication for balancing blood sugar, has mixed reviews when it comes to postoperative care.

Evidence suggests that metformin may increase the risk of a potentially fatal condition called lactic acidosis, which is a buildup of lactic acid in the blood. This condition primarily affects people with impaired kidney function in addition to their diabetes. For patients with neither condition, this is a very rare complication.

No safety guidelines exist about metformin use and surgery, but some sources recommend discontinuing the drug for up to 48 hours before surgery. The American Diabetes Association recommends withholding metformin on the day of surgery.

Some healthcare providers don't tell their patients to stop taking metformin before surgery unless they also have major risk factors for lactic acidosis, including severe problems with their kidneys, liver, or lungs.

Other medications called SGLT2 inhibitors (gliflozins) may increase the risk of a potentially fatal condition called diabetic ketoacidosis. The medication, in combination with another trigger such as surgery, makes your body break down fat at a dangerous speed. Your body then tries to burn it off, which causes your liver to produce ketones. The ketones build up in your blood and make it acidic.

People with type 1 diabetes are at a much higher risk of surgically triggered ketoacidosis than those with type 2.

Insulin Effects

If you take insulin, talk to your surgeon as well about what dose you should take the night before and/or the morning of your surgery. Both hyperglycemia (having too much glucose in the blood) and hypoglycemia (having too little glucose in the blood) can be dangerous for surgery.

To avoid these and other possible complications, be sure to provide your healthcare provider with your complete list of current prescriptions, over-the-counter medications, and supplements.

Post-Surgery Management Tips

Your diabetes needs to be well controlled after your surgery as well to prevent complications such as wound infections, slow healing, and increased scarring.

If you're not consistent about taking care of yourself, taking medications as prescribed, and routinely checking your glucose levels, seek help from your healthcare team. They can work with you on an effective treatment plan.

A lot of factors can make it difficult to eat regularly while you're in the hospital, such as vomiting, lack of appetite, stress, or pain. If you're not eating well or if you've been prescribed medications that may increase your blood sugar, you may need to stay longer for blood-sugar monitoring.

Keep in mind that the following are essential to a quick and healthy recovery:

  • Eating appropriate foods after surgery (whole grains, fruits, vegetables, and lean protein)
  • Frequently checking your glucose levels
  • Taking your insulin or other diabetes medications as prescribed

Exercise can also help control glucose levels and is an important part of recovery for people with or without diabetes. Your surgeon will be the best judge of what type of physical activity is possible after surgery and how quickly you can attempt more strenuous exercise during your recovery. 

Simply checking your glucose levels more frequently than usual is one change in your daily routine that may have the single largest impact on how well and how quickly you heal after surgery.

A Word From Verywell

Surgery becomes more complicated when you have diabetes, for a number of different factors. It is worth the time and effort to work to control your glucose levels—both before and after surgery—to maintain good health. Doing so can help your body heal faster and avoid infection—a sure bonus during the post-operative period.

11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Jennifer Whitlock, RN, MSN, FN
Jennifer Whitlock, RN, MSN, FNP-C, is a board-certified family nurse practitioner. She has experience in primary care and hospital medicine.