Diabetes mellitus is a group of chronic, etiopathogenetically heterogeneous diseases, the main feature of which
is hyperglycemia. It is accompanied by a complex disorder of the metabolism of carbohydrates, fats and proteins.
Secondarily, a hydromineral metabolism disorder occurs. Stable blood glucose concentration within the physiological
range is essential for the normal functioning of the body. Conditions associated with acute or chronic deviations
in the sense of hyper or hypoglycemia significantly alters the state of health of the patient. Factors influencing metabolic
status and glycemia, such as the disease itself, type of surgery, stroke, infection and administration of anesthetics
or various medications, should be considered. Parenteral nutrition must be individually tailored to the patient’s
nutritional status, current needs of the patient, and organ complications. Hyperglycemia is closely associated
with many debilitated clinical outcomes in critically ill patients in hospital care. Despite the unbalanced outcome of
clinical trials, attempting to achieve normoglycemia remains an important role in hospitalized patients. Less strict
glycemic goals lead to a reduced number of hypoglycemia, which is a clinical benefit. Good glycemic compensation
improves the condition of patients. Hyperglycaemia and hypoglycaemia, and in particular frequent fluctuations
– glycemic variability are markers of worse prognosis for critically and not critically ill patients.