Causes
Hyperglycemia may be caused by: diabetes, various (non-diabetic) endocrine disorders (insulin resistance and thyroid, adrenal, pancreatic, and pituitary disorders), sepsis and certain infections, intracranial diseases (e.g. encephalitis, brain tumors (especially if near the pituitary gland), brain haemorrhages, and meningitis) (frequently overlooked), convulsions, end-stage terminal disease, prolonged/major surgeries, excessive eating, severe stress, and physical trauma. Endocrine
Chronic, persistent hyperglycaemia is most often a result of diabetes. Several hormones act to increase blood glucose levels and may thus cause hyperglycaemia when present in excess, including: cortisol, catecholamines, growth hormone, glucagon, and thyroid hormones. Hyperglycaemia may thus be seen in: Cushings syndrome, pheochromocytoma, acromegaly, hyperglucagonemia, and hyperthyroidism. Diabetes mellitus
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.In diabetes mellitus, hyperglycemia is usually caused by low insulin levels (diabetes mellitus type 1) 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.
In general, the normal range for most people (fasting adults) is about 4 to 6 mmol/L or 80 to 110 mg/dL. (where 4 mmol/L or 80 mg/dL is "optimal".) A subject with a consistent range above 7 mmol/L or 126 mg/dL is generally held to have hyperglycemia, whereas a consistent range below 4 mmol/L or 70 mg/dL is considered hypoglycemic. In fasting adults, blood plasma glucose should not exceed 7 mmol/L or 126 mg/dL. 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 (mg/dL levels from 144 to 270).Defects in insulin secretion, insulin action, or both, results in hyperglycemia. Chronic hyperglycemia can be measured by clinical urine tests which can detect sugar in the urine or microalbuminuria which could be a symptom of diabetes. Treatment
Treatment of hyperglycemia requires elimination of the underlying cause, such as diabetes. Acute hyperglycemia can be treated by direct administration of insulin in most cases. Severe hyperglycemia can be treated with oral hypoglycemic therapy and lifestyle modification. In diabetes mellitus (by far the most common cause of chronic hyperglycemia), treatment aims at maintaining blood glucose at a level as close to normal as possible, in order to avoid serious long-term complications.