Parenteral nutrition is the supply of all or a part of daily nutrient needs via direct infusion into the blood. A patient may need nutritional support when they cannot eat sufficiently due to intestinal failure caused by disease or surgery. Common causes of intestinal failure are trauma, burns, pancreatitis, cancer, inflammatory bowel disease and short bowel syndrome. 

Parenteral nutrition may be composed of carbohydrates, fat or lipid, protein and micronutrients. These components can supply all of a patient's nutritional requirements or may be used to supplement other nutritional intake. Historically these solutions were supplied individually via a y-site. However "All-in-one" solutions are now available as either off-the-shelf convenience products or compounded solutions to meet specific patient requirements.

Parenteral nutrition can be administered via a central or peripheral vein, the former being more common in the Australian healthcare system.