Nil per os (also /Nihil/Non/Nulla Per Orem) (NPO) is Latin for a medical instruction meaning to withhold oral food and fluids from a patient for various reasons (verbatim it translates: "nothing through the mouth" or "not through the mouth"). In the UK it is translated as Nil By Mouth (NBM). Typical reasons for NPO instructions are the prevention of aspiration pneumonia, e.g. in those who will undergo general anaesthetic, or those with weak swallowing musculature, or in case of gastrointestinal bleeding or gastrointestinal blockage. Alcohol overdoses that result in vomiting also warrant NPO instructions for a period of time.
