Parenteral nutrition provides all essential nutrients directly into the blood stream without involvement of the gastrointestinal tract if conventional oral or enteral nutrition is not possible. The awareness of how important it is to provide adequate nutrition to the ill has accompanied people for a long time, as evidenced by the first attempts to conduct nutrition by bypassing the gastrointestinal tract taken as early as in the seventeenth century. The contemporary methods of nutrition have been established in the twentieth century and are still being improved. Nutrition is carried out using specially prepared formulations containing all necessary nutrients in the most absorbable form. These mixes are adapted to individual requirements, resulting from the underlying disease. They are available in the form of ready-made preparations or separate bottles. A method of nutrition is selected on the basis of its expected duration. Disease states are associated with increased catabolism with greater demand for energy and nutrients. This often leads to the development or exacerbation of malnutrition which affects convalescence after surgery and the general condition of the patient as well as increases the risk of hospital complications. As any medical procedure, parenteral nutrition is associated with a risk of side effects. However, the principles of care of the injection site and preparation of appropriate mixes tailored to patient’s needs help minimise the risk of adverse reactions. It is necessary to detect malnutrition early, estimate risk, create nutrition plans and include nutrition to therapy, which will improve the condition of hospitalised patients, accelerate their recovery, shorten hospital stay and reduce treatment costs.