Chronic hyperglycemia that persists even in fasting states is most commonly caused
by diabetes mellitus. In fact, chronic hyperglycemia is the defining characteristic of the disease.
Intermittent hyperglycemia may be present in prediabetic states. Acute episodes of hyperglycemia
without an obvious cause may indicate developing diabetes or a predisposition to the disorder.
and/or by resistance to insulin at the cellular level (Diabetes mellitus type 2), depending on the type
and state of the disease. Low insulin levels and/or insulin resistance prevent the body from
converting glucose into glycogen (a starch-like source of energy stored mostly in the liver), which in
turn makes it difficult or impossible to remove excess glucose from the blood. With normal glucose
levels, the total amount of glucose in the blood at any given moment is only enough to provide
energy to the body for 20–30 minutes, and so glucose levels must be precisely maintained by the
body’s internal control mechanisms. When the mechanisms fail in a way that allows glucose to rise
to abnormal levels, hyperglycemia is the result.
Ketoacidosis may be the first symptom of immune-mediated diabetes, particularly in children and
adolescents. Also, patients with immune-mediated diabetes, can change from modest fasting
hyperglycemia to severe hyperglycemia and even ketoacidosis as a result of stress or an infection.