Hyperglycemia is often found in diabetes mellitus. It occurs when the body does not have enough insulin or cannot use the insulin it has to turn glucose into energy. Hyperglycemia may also occur in Cushing's syndrome and other conditions.
The term "hyperglycemia" comes from the Greek "hyper-" = high, over, beyond, above + "glykys" = sweet + "haima" = blood. High sweetness (sugar) in the blood.