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Prescription / Chart Abbreviation🐕 Dogs🐈 Catsgastrointestinal

NPO (Nothing by Mouth)

🗣️ Pronounced:N-P-O / nil per OSS
In One Sentence (Plain English)

A medical directive from Latin "nil per os," meaning nothing should be given by mouth (no food, treats, or water) for a specified period.

Editorial Status: Verified from peer-reviewed veterinary sources (v1.0)
Updated: 2026-01-15

💬 In Plain English

NPO stands for "nil per os," which is Latin for "nothing by mouth." When your veterinarian marks your pet as NPO—most commonly the night before surgery or general anesthesia—it means your pet must not eat any food, treats, chews, or table scraps. Under general anesthesia, pets lose their natural swallowing reflexes. If there is food in the stomach, they can vomit or passively regurgitate, causing food particles and stomach acid to be inhaled into the lungs (pulmonary aspiration), which is a life-threatening complication.

🔬 Clinical & Technical Depth

For Vets & Technicians

Formal Clinical Definition

Medical instruction originating from Latin "nil per os" (nothing by mouth). Enforces pre-anesthetic fasting or complete gastrointestinal rest during active vomiting, megaesophagus, or prior to gastrointestinal procedures.

Why Veterinarians Use It

Veterinarians enforce NPO to minimize the risk of anesthetic regurgitation and catastrophic aspiration pneumonia, or to rest the gut during acute intractable vomiting.

Clinical Context Encountered

Given to pet owners as pre-operative instructions before surgery, dental cleanings, or sedated imaging procedures.

Clinical Reference Guide (Prescription / Chart Abbreviation)

Full ExpansionNil Per Os (Latin for "nothing by mouth")

Withhold all food, treats, and snacks from the animal for the designated time period.

Where You Encounter It

  • Pre-operative instructions prior to surgery, dental cleanings, or sedated imaging
  • Patients with intractable, acute vomiting (resting the gastrointestinal tract)
  • Esophageal foreign body or megaesophagus workups
🚨 Red Flag Warnings (When to Contact an Emergency Vet)
  • •If your pet accidentally ate breakfast, grabbed a treat, or raided the garbage on the morning of scheduled surgery, ALWAYS be completely honest and tell the veterinary surgical team immediately—anesthesia may need to be rescheduled for your pet’s safety.

❓ Questions to Ask Your Veterinarian

Take these actionable questions with you to your next clinic visit or appointment:

  • 1At what exact time the night before surgery should food be picked up (typically midnight or 8 to 12 hours prior)?
  • 2Is my pet allowed access to water overnight, or should water also be removed in the morning?
  • 3If my pet is a pediatric puppy/kitten, diabetic, or a toy breed, should the fasting period be shortened to prevent low blood sugar (hypoglycemia)?
  • 4Should my pet’s regular morning medications (such as heart or seizure pills) be given with a tiny sip of water or withheld?

Academic & Clinical References