Expand: date=January 2007

Hyperglycemia, hyperglycaemia, or high blood sugar is a condition in which an excessive amount of glucose circulates in the blood plasma. This is generally a blood glucose level of 10+ mmol/L, but symptoms and effects may not start to become noticable until later numbers like 15-20+ mmol/L.

The origin of the term is Greek: hyper-, meaning excessive; -glyc-, meaning sweet; and -emia, meaning "of the blood".

Diabetes mellitus

Chronic hyperglycemia that persists even in fasting states is most commonly caused by diabetes mellitus, and in fact chronic hyperglycemia is the defining characteristic of the disease. Acute episodes of hyperglycemia without an obvious cause may indicate developing diabetes or a predisposition to the disorder. This form of hyperglycemia is caused by low insulin levels. These low insulin levels inhibit the transport of glucose across cell membranes therefore causing high blood glucose levels.

Eating disorders

Certain eating disorders can produce acute non-diabetic hyperglycemia, as in the binge phase of bulimia nervosa, when the subject consumes a large amount of calories at once, frequently from foods that are high in simple and complex carbohydrates. Certain medications increase the risk of hyperglycemia, including beta blockers, thiazide diuretics, corticosteroids, niacin, pentamidine, protease inhibitors, L-asparaginase, and some antipsychotic agents.

A high proportion of patients suffering an acute stress such as stroke or myocardial infarction may develop hyperglycemia, even in the absence of a diagnosis of diabetes. Human and animal studies suggest that this is not benign, and that stress-induced hyperglycemia is associated with a high risk of mortality after both stroke and myocardial infarction.

Times of Physiologic Stress

Hyperglycemia occurs naturally during times of infection and inflammation. When the body is stressed, endogenous catecholamines are released that - amongst other things - serve to raise the blood glucose levels. The amount of increase varies from person to person and from inflammatory response to response. As such, no patient with first-time hyperglycemia should be diagnosed immediately with diabetes if that patient is concomitantly sick. Further testing, such as a fasting plasma glucose, random plasma glucose, or two-hour postprandial plasma glucose level, must be performed.

Measurement and definition

Glucose levels are measured in either:

1. Milligrams per deciliter (mg/dL), in the United States and other countries (e.g., Japan, France, Egypt, Colombia); or
2. Millimoles per liter (mmol/L), which can be acquired by dividing (mg/dL) by factor of 18.

Scientific journals are moving towards using mmol/L; some journals now use mmol/L as the primary unit but quote mg/dl in parentheses.