Nil per os

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Nil per os (alternatively nihil/non/nulla per os) (npo or NPO) is a medical instruction meaning to withhold oral food and fluids from a patient for various reasons. It is a Latin phrase whose usual English expansion is nothing by mouth (most literally, "nothing through the mouth"). Variants include nil by mouth (NBM).

NPO is one of the abbreviations that is not used in AMA style; "nothing by mouth" is spelled out instead.


The typical reason for NPO instructions is the prevention of aspiration pneumonia, e.g. in those who will undergo general anesthesia, or those with weak swallowing musculature, or in case of gastrointestinal bleeding, gastrointestinal blockage, or acute pancreatitis. Alcohol overdoses that result in vomiting or severe external bleeding also warrant NPO instructions for a period.

"Pseudo-NPO" orders are often used after gastrointestinal and/or dental surgeries, in which the patient is limited to a soft-food diet or given a list of foods/types of food to specifically avoid (I.E. grapefruit and grapefruit juice before and after surgery).


Pre-surgery NPO orders are typically between 6 and 12 hours prior to surgery, through recovery suite discharge, but may be longer if long acting medications or oral post-meds were administered. It is not uncommon for the food NPO period to be longer than that for liquid, as the American Board of Anesthesiology advises against liquid NPO periods greater than eight hours.[citation needed] The NPO periods for illness tend to be much longer, although exceptions are made for small scheduled amounts of water consumption if an IV drip is not in use. With sufficient IV fluids, NPO periods of several days have been utilized successfully in non-diabetic patients (although short NPO periods in diabetics are possible with IV fluids, insulin, and dextrose (see below).[citation needed] Extended periods (greater than 12 hours) are still contraindicated.

The American Board of Anesthesiology recommends that patients should not eat solid food for at least 8 hours prior to a procedure, and should not drink even clear liquids for at least 2 hours prior.[1]

For extended periods without food or water, patients may be started on total parenteral nutrition (TPN).

See also[edit]


  1. ^ Apfelbaum, Jeffrey; Caplan, Robert; Connis, Richard; Epstein, Burton; Nickinovich, David; Mark, Warner (March 2011). "Practice Guidelines for Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration: Application to Healthy Patients Undergoing Elective Procedures" (PDF). Anesthesiology 114 (3): 498–499. Retrieved 4 January 2016.