NPO is a hospital abbreviation for the Latin phrase “nil per os,” which translates to “nothing by mouth.” When a doctor places you on NPO status, it means you cannot eat or drink anything until the restriction is lifted. In some cases, it also means you cannot take oral medications. You’ll most commonly encounter this order before surgery, certain imaging tests, or specific blood draws.
Why Hospitals Require NPO Status
The most common reason for an NPO order is to keep your stomach empty before a procedure that involves anesthesia or sedation. When you’re under anesthesia, the reflexes that normally prevent food and liquid from entering your lungs stop working. If there’s anything in your stomach, it can travel back up into your throat and slip into your airways, a dangerous complication called pulmonary aspiration. This can cause serious lung damage or infection.
NPO orders also apply outside of surgery. Several diagnostic tests require an empty stomach for accurate results. Gallbladder imaging studies require at least 4 hours of fasting. Thyroid scans need a minimum of 6 hours without food or drink. Certain kidney scans allow water but restrict food for 4 hours beforehand. Fasting blood tests, like those measuring blood sugar, also need you to skip eating so results aren’t thrown off by a recent meal.
How Long You Need to Fast
The old standard was a blanket “nothing after midnight” rule for anyone having surgery the next day. Current guidelines from the American Society of Anesthesiologists are more specific and, for many patients, less restrictive. The timelines depend on what you consume:
- Clear liquids: allowed up to 2 hours before the procedure
- Breast milk (for infants): allowed up to 4 hours before
- Infant formula, light meals, or non-human milk: allowed up to 6 hours before
- Fried foods, fatty foods, or meat: may require 8 or more hours of fasting
These timelines apply to elective procedures involving general anesthesia, regional anesthesia, or sedation. Your surgical team may give you a more conservative window depending on your specific health conditions or the type of procedure, so always follow the instructions you receive directly.
What Counts as a Clear Liquid
When hospital staff say you can still have “clear liquids” up to a certain time, they mean liquids you can see through at room temperature. That includes water, broth, plain tea and coffee (no cream or milk), gelatin, popsicles, pulp-free juice, sodas, and sports drinks. Anything with milk, cream, pulp, or solid particles does not count. Orange juice with pulp, a smoothie, or coffee with creamer would all break your NPO status.
What About Medications, Teeth Brushing, and Gum
One of the trickiest parts of being NPO is figuring out what to do with daily medications. Some essential drugs, like those for blood pressure or heart rhythm, may still need to be taken on schedule. The typical approach is to swallow them with a small sip of water. However, there’s no universal rule here. Your care team should give you a specific list of which medications to take and which to skip. If nobody has told you, ask before your procedure rather than guessing.
You can brush your teeth while NPO. Stony Brook Medicine’s surgical guidelines, which reflect common hospital practice, say you may brush and rinse your mouth with a small sip of water as long as you spit it out and don’t swallow. Chewing gum, on the other hand, is off limits on the day of your procedure. It stimulates stomach acid production and can trigger swallowing, both of which work against the purpose of fasting.
What Happens If You Eat or Drink
If you break your NPO status, your procedure will likely be delayed or canceled entirely. Estimated cancellation rates on the day of surgery run as high as 18% across studies, though not all of those are from fasting violations. Even at hospitals with lower cancellation rates (around 1.5% in one large review), NPO violations remain a frequent cause of disruption. A delay means rescheduling, which creates stress for you and your family, adds cost, and pushes back your treatment timeline.
More importantly, proceeding with anesthesia on a full stomach is genuinely dangerous. Aspiration can lead to pneumonia, lung injury, or in rare cases, life-threatening complications. Anesthesiologists take this seriously, and if there’s any doubt about when you last ate, they will postpone the procedure rather than take the risk.
Fasting Rules for Infants and Children
Pediatric fasting follows the same general framework but with adjustments for how babies and young children eat. Most hospitals allow clear fluids up to 2 to 3 hours before anesthesia for children of any age. Breast milk is typically restricted to 4 hours before the procedure for infants. Formula generally requires a 6-hour fast, though some hospitals use a 4-hour window for babies under 6 months.
For solid foods in older children, many hospitals still default to the “nothing after midnight” approach, especially for kids over age 3. There’s actually no universal agreement among hospitals on exact fasting times for solids in younger children, so you may get slightly different instructions depending on where your child’s procedure takes place. Follow whatever your surgical team specifies, and if your child accidentally eats or drinks outside the allowed window, let the team know immediately rather than hoping it won’t matter.