Hyperglycemia refers to an abnormally high blood sugar. The blood sugar can be measured either at the bedside or in the lab.

A healthy baby's body usually has very careful control of blood glucose levels. Insulin is the main hormone in the body that regulates glucose. Sick babies may have poor insulin function or low amounts, which causes poor control of the blood sugar.

There can be specific causes of ineffective or low insulin, such as infection, liver problems, hormone problems, and some medications. Rarely, babies may actually have diabetes, with low insulin levels that result in high blood sugars.

There are frequently no signs in babies with hyperglycemia -- the diagnosis is made when a blood test measures the glucose and it is high. Sometimes, babies with high blood sugars will produce high amounts of urine and get dehydrated due to high blood sugars. In addition, new onset of high blood sugars may be an indication that the baby has some new stress, such as an infection or heart failure.

On the short-term, prolonged periods of hyperglycemia may cause high urine output with dehydration. There are usually no long-term effects from high blood sugars unless the baby actually has diabetes.