Hyperglycemia (High Blood Sugar): Symptoms & Signs

Hyperglycemia is the term that refers to an abnormally high level of sugar, or glucose, in the blood. Diabetes mellitus types 1 and 2 are by far the most common causes of hyperglycemia. In patients with either type 1 or type 2 diabetes, metabolic abnormalities lead to an elevation in blood glucose levels. When there is too much glucose in the blood, this can lead to a number of health risks and other symptoms. The main symptoms associated with hyperglycemia are

A severe elevation in blood glucose level can be life-threatening. This represents a medical emergency like diabetic ketoacidosis (DKA) or hyperglycemic hyperosmolar nonketotic syndrome (HHNS, also referred to as hyperglycemic hyperosmolar state). Some symptoms of hyperglycemia occur when the hyperglycemia is present for a long time, such as poor wound healing and weight loss. In emergencies like diabetic ketoacidosis, symptoms include nausea, vomiting, abdominal pain, confusion, shortness of breath, and a fruity odor to the breath.

Causes of hyperglycemia

Type 1 or type 2 diabetes is the most common cause of hyperglycemia. Other causes can include pancreatitis, Cushing's syndrome, unusual hormone-secreting tumors, pancreatic cancer, certain medications, and severe illnesses.


Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.

Medically Reviewed by a Doctor on 3/6/2017

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