High blood sugar can occur after surgery, especially if you have diabetes. It can increase the risk of infection, delayed healing, and other serious complications.

Each year, 310 million major surgeries are performed across the world, and 40–50 million occur in the United States. Surgery comes with some risks, including high blood sugar, also known as hyperglycemia.

Hyperglycemia can negatively affect healing after surgery, so it’s important to take steps to reduce the risk of it occurring.

If you have diabetes, talk with your doctor about a plan for managing your blood sugar levels before, during, and after surgery.

Before and after surgery, your blood sugar levels may fluctuate because of:

  • mental and physical stress of having the operation
  • lifestyle changes, including dietary and exercise adjustments
  • medication changes necessary for the procedure

Note that if you have diabetes, you may be particularly at risk of blood sugar fluctuation following surgery.

Your blood sugar levels may rise because of your body’s stress responses during surgery. The physical toll of surgery and anesthesia can cause your body to release greater amounts of the hormones catecholamine, cortisol, and glucagon.

As these hormone levels rise, your body can experience greater insulin resistance and an increase in the amount of glucose in the blood. This increased insulin resistance may last for 9–21 days after surgery.

If you have diabetes, you have a greater risk of experiencing blood sugar fluctuations during surgery, but these changes can happen to any individual, especially if the surgery is longer or more invasive.

Your doctor may suggest eating more carbohydrates before surgery to help sustain you throughout the procedure and to counteract any insulin resistance.

If you have hyperglycemia after surgery, it’s important to:

  • Check your blood sugar levels frequently.
  • Eat nutritious foods from a variety of food groups.
  • Take any medications — including insulin and diabetes medications — as prescribed.
  • Exercise in ways that are safe and recommended by medical professionals.

If you use an insulin pump to help manage your diabetes, it’s important to let your doctor know before surgery. Whether or not you can continue to use the pump will depend on the specific type of pump and the surgery being performed.

Talk with your healthcare team about specific issues related to wearing an insulin pump during your procedure. In general, many surgical teams prefer to turn off insulin pumps during emergency surgeries and keep them on during elective surgeries.

However, this doesn’t always apply, as insulin pump use and continuous glucose monitors have become more common in recent years. It’s best to consult with your doctor before your procedure.

Stress hyperglycemia is a term for temporary elevations in blood sugar levels. This may be due to acute illness, stress, or surgery, and it can affect people who do not have diabetes.

Research from 2017 defines stress hyperglycemia after surgery as blood glucose levels greater than 140 milligrams per deciliter (mg/dL) or 180 mg/dL in individuals with prior normal blood glucose levels within 48 hours of having surgery.

Stress hyperglycemia should be monitored after surgery to prevent serious complications.

According to research from 2015, post-operative complications of hyperglycemia can include:

If you have high blood sugar levels following your procedure, your doctor may use an IV to infuse you with insulin. They may also recommend undergoing frequent blood sugar testing, following a well-balanced and nutritious diet, taking prescribed medications, and exercising to manage your risk of hyperglycemia after surgery.

Does anesthesia cause high blood sugar levels?

Anesthesia can put stress on the body and result in elevated blood sugar levels.

Researchers are continuing to determine how certain types of anesthesia can affect people’s blood sugar levels during and after surgery.

Can you develop diabetes after surgery?

It’s not uncommon for individuals to experience high blood sugar following surgery as a result of the body’s stress responses. Changes in diet, exercise, and medications related to surgery can also cause blood sugar level changes.

However, as their healing progresses, people without diabetes should notice their blood sugar levels return to a normal range.

What happens if you have low blood sugar after surgery?

If you have hypoglycemia, or low blood sugar, after surgery, your doctor may give you 10–15 grams of oral carbohydrates to rapidly raise your glucose levels and relieve symptoms. If your blood sugar levels become dangerously low, they may administer glucagon for a fast boost in blood sugar levels.

Hyperglycemia after surgery can affect healing time and increase your risk of infection.

For people with diabetes, it’s especially important to monitor blood sugar levels before, during, and after surgery.

To help reduce the risk of hyperglycemia after surgery, it’s important to take any prescribed medications, follow a well-balanced, nutritious diet, and exercise as recommended by your healthcare team.