Nil per os (alternatively nihil/non/nulla per os) (NPO) is a medical instruction meaning to withhold oral food and fluids from a patient for various reasons. It is a Latin phrase which translates as "nothing 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.

When patients are placed on NPO orders prior to surgical general anaesthesia, physicians would usually add the exception that patients are allowed a very small drink of water to take with their usual medication. This is the only exception to a patient's pre-surgery NPO status. Otherwise, if a patient accidentally ingested some food or water, the surgery would usually be cancelled or postponed for at least 8 hours.

[edit] See also

• Per os
• Preoperative fasting
• List of Latin phrases
• Medical prescription

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