Final answer:
TPN, or total parenteral nutrition, is administered intravenously to deliver nutrients directly into the bloodstream when a patient is unable to obtain nutrition through the gastrointestinal tract.
Step-by-step explanation:
TPN, or total parenteral nutrition, is a method of delivering nutrients to a patient when they are unable to obtain nutrition through the gastrointestinal tract. It involves providing nutrients directly into the bloodstream through intravenous administration. TPN is not given subcutaneously, orally, or intramuscularly.