What Causes a Blood Sugar Rise After Surgery?

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Surgery can be a stressful experience, especially for diabetics. It’s quite common to have a blood sugar rise after surgery in people who have diabetes and sometimes in normal people too. What causes this blood sugar rise after surgery?


Any type of stress makes blood sugars more difficult to control, including the stress of surgery. When diabetics are stressed for any reason, their body pumps out hormones that alter blood sugar levels – causing blood sugars to go up or down. Sometimes medications doctors give during or after surgery, particularly steroids, cause blood sugar levels to rise. Although high blood sugar levels are more common after surgery, hypoglycemia or low blood sugars can also occur in some cases.

It’s critical to control blood sugars after surgery since diabetics with high blood sugars are at a higher risk of complications including post-surgical infection and poor wound healing. Diabetics have up to a five times greater risk of developing a wound infection than non-diabetics and poorly controlled blood sugars elevates the risk even more. Poorly controlled blood sugars are especially common after heart surgery, and very high blood sugar levels increases mortality after such a procedure. Obviously, it’s important for doctors to treat these blood sugar rises to increase the chances of a good outcome.

How Are Rises in Blood Sugar After Surgery Controlled?

After surgery, doctors and nurses monitor glucose levels more frequently and adjust insulin dosages based on the results. The goal now is to keep blood sugar levels less than 180 milligrams per deciliter since blood sugars above this level increase the risk of complications such as infection. At one time, doctors tried to keep blood glucose levels between 80 and 110 milligrams per deciliter after surgery, but very tight blood glucose control is no longer recommended since it doesn’t reduce overall mortality – and may increase it. Now the focus has shifted to keeping blood sugar levels between 120 and 150 milligrams per deciliter.

For some diabetics in the surgical intensive care unit after surgery, doctors give intravenous insulin to better control blood sugars. In other cases, they simply adjust subcutaneous insulin doses based on blood sugar levels. The more frequently blood sugar levels can be monitored, the better.

Some hospitals now monitor blood sugar levels continuously using a special sensor placed under the skin. This system gives blood sugar readings every five minutes, which allows more frequent adjustments of insulin dosages. An insulin pump can also be used in conjunction with continuous glucose monitoring for even tighter blood sugar control.

The Bottom Line?

Rises in blood sugar after surgery are common and when they rise too high it increases the risk of infection and other complications. On the other hand, doctors are moving away from very tight glucose control, because it doesn’t offer any advantages and may increase the risk of hypoglycemia. Moderate blood glucose control after surgery is becoming the new standard.


Hospitalist News. “Moderate Glucose Target May Reduce Deaths : Moderate blood glucose control was linked to a significant 40% reduced mortality after CABG.”

Merck Manual. 18th Edition. 2006.