Hyperglycemia

Hyperglycemia, hyperglycaemia, or high blood sugar is a condition in which an excessive amount of glucose circulates in the blood plasma.

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

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Causes

Diabetic hyperglycemia

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.

Non-diabetic hyperglycemia

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,^[1] and some antipsychotic agents.^[2]

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.^[3]

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.^[4]

Comparatively:^[5]

• 72 mg/dL = 4 mmol/L
• 90 mg/dL = 5 mmol/L
• 108 mg/dL = 6 mmol/L
• 126 mg/dL = 7 mmol/L
• 144 mg/dL = 8 mmol/L
• 180 mg/dL = 10 mmol/L
• 270 mg/dL = 15 mmol/L
• 288 mg/dL = 16 mmol/L
• 360 mg/dL = 20 mmol/L
• 396 mg/dL = 22 mmol/L
• 594 mg/dL = 33 mmol/L

Glucose levels vary before and after meals, and at various times of day; the definition of "normal" varies among medical professionals. In general, the normal range for most people (fasting adults) is about 80 to 120 mg/dL or 4 to 7 mmol/L. A subject with a consistent range above 126 mg/dL or 7 mmol/L is generally held to have hyperglycemia, whereas a consistent range below 70 mg/dL or 4 mmol/L is considered hypoglycemic. In fasting adults, blood plasma glucose should not exceed 126 mg/dL or 7 mmol/L. Sustained higher levels of blood sugar cause damage to the blood vessels and to the organs they supply, leading to the complications of diabetes.

Chronic hyperglycemia can be measured via the HbA1c test. The definition of acute hyperglycemia varies by study, with mmol/L levels from 8 to 15.^[6][7]

Symptoms of hyperglycemia

The following symptoms may be associated with acute or chronic hyperglycemia, with the first three comprising the classic hyperglycaemic triad:

• Polyphagia - frequent hunger, especially pronounced hunger
• Polydipsia - frequent thirst, especially excessive thirst
• Polyuria - frequent urination, especially excessive urination
• Blurred vision
• Fatigue
• Weight loss
• Poor wound healing (cuts, scrapes, etc.)
• Dry mouth
• Dry or itchy skin
• Impotence (male)
• Recurrent infections such as vaginal yeast infections, groin rash, or external ear infections (swimmer's ear)

Frequent hunger without other symptoms can also indicate that blood sugar levels are too low. This may occur when people who have diabetes take too much oral hypoglycemic medication or insulin for the amount of food they eat. The resulting drop in blood sugar level to below the normal range prompts a hunger response. This hunger is not usually as pronounced as in Type I diabetes, especially the juvenile onset form, but it makes the prescription of oral hypoglycemic medication difficult to manage.

Polydipsia and polyuria occur when blood glucose levels rise high enough to result in excretion of excess glucose via the kidneys (glycosuria), producing osmotic diuresis.

Symptoms of acute hyperglycemia may include:

• Ketoacidosis
• A decreased level of consciousness or confusion
• Dehydration due to glycosuria and osmotic diuresis
• Acute hunger and/or thirst
• Impairment of cognitive function, along with increased sadness and anxiety^[8][9]

Treatment

Treatment of hyperglycemia requires elimination of the underlying cause, e.g., treatment of diabetes when diabetes is the cause. Acute and severe hyperglycemia can be treated by direct administration of insulin in most cases, under medical supervision.

See also

• Hypoglycemia
• Glucose
• Diabetes

References