[3][4][5][6] Patients with diabetes are oriented to avoid exceeding the recommended postprandial threshold of 160 mg/dL (8.89 mmol/L) for optimal glycemic control.

These values are higher than the renal threshold of 10 mmol/L (180 mg/dL) up to which glucose reabsorption is preserved at physiological rates[3][10][11] and insulin therapy is not necessary.

Blood glucose levels can rise well above normal and cause pathological and functional changes for significant periods without producing any permanent effects or symptoms.

[16] Acute hyperglycemia involving glucose levels that are extremely high is a medical emergency and can rapidly produce serious complications (such as fluid loss through osmotic diuresis).

The resulting drop in blood sugar level to below the normal range prompts a hunger response.

[20] In untreated hyperglycemia, a condition called ketoacidosis may develop because decreased insulin levels increase the activity of hormone sensitive lipase.

[21] The degradation of triacylglycerides by hormone-sensitive lipase produces free fatty acids that are eventually converted to acetyl-coA by beta-oxidation.

In addition, it reduces skin graft success, exacerbates brain, spinal cord, and renal damage by ischemia, worsens neurologic outcomes in traumatic head injuries, and is associated with postoperative cognitive dysfunction following CABG.

Hyperglycemia also leads to biochemical changes in the body; both of these factors result in increased severity of respiratory infections and vulnerability to pathogens.

Importantly, hyperglycemia affects the function of neutrophils, which are white blood cells responsible for responding to infection.

This is because hyperglycemia impacts a few factors such as microenvironment of immune cells, or even bacteria's supply of energy, adding on stress to the bacterial proliferation metabolism.

[24] The chronic inflammatory state induced by high glucose levels can also lead to dysfunction in various parts of the immune system.

For example, advanced glycation end products (AGEs), which are more prevalent in hyperglycemic conditions, can interfere with the normal function of the immune system and contribute to the pathogenesis of infections.

For instance, elevated blood glucose levels can actively contribute to pathophysiology of this disease, by exacerbating existing inflammation, impairing cellular immune responses, and increasing oxidative stress, which can also lead to more severe infection.

In addition, patients with acute hyperglycemia who don't have a history of diabetes can experience higher rates of mortality and complications.

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,[28] stress,[29] and excessive eating of carbohydrates.

[41] Certain medications increase the risk of hyperglycemia, including: corticosteroids, octreotide, beta blockers, epinephrine, thiazide diuretics, statins, niacin, pentamidine, protease inhibitors, L-asparaginase,[42] and antipsychotics.

[16] A high proportion of patients with an acute stress such as stroke or myocardial infarction may develop hyperglycemia, even in the absence of a diagnosis of diabetes.

)[citation needed] 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.

Acute hyperglycemia can be treated by direct administration of insulin in most cases and may be lessened by the intake of some natural compounds.

For example, a single dose of raw cinnamon before a meal containing complex carbohydrates decreases the postprandial hyperglycemia (higher than 140 mg/dL; >7.8 mmol/L) in patients with type II diabetes.

[52] 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.

Low-middle income groups are more likely to develop hyperglycemia, due in part to a limited access to education and a reduced availability of healthy food options.

[63] The origin of the term is Greek: prefix ὑπέρ- hyper- "over-", γλυκός glycos "sweet wine, must", αἷμα haima "blood", -ία, -εια -ia suffix for abstract nouns of feminine gender.