NPO Diet: A Beginner’s Guide

Has your doctor told you that you’re NPO?

This means that you cannot eat or drink anything for a certain period.

Your doctor may place you NPO for various reasons, such as before a procedure or to manage symptoms like nausea and vomiting.

However, while an NPO diet has its purpose, it tends to be prescribed unnecessarily and for too long.

This article discusses situations in which an NPO diet is necessary and for which reasons it may be unnecessary.

NPO diet

What is an NPO diet?

NPO is an acronym for “nil per os,” a Latin phrase that translates to nothing by mouth.

When you’re “placed NPO” it means that you cannot eat or drink anything — including water or ice chips, unless allowed by the doctor — for a certain time.

Doctors generally place a patient NPO several hours before and or after a procedure to minimize the risk of aspiration from anesthesia, which occurs when stomach contents enter your lungs. Anesthesia-related aspiration can be deadly (1).

An NPO diet is also commonly prescribed during active phases of inflammatory digestive conditions like acute pancreatitis and diverticulitis to provide the bowels with rest and manage symptoms like vomiting.

Once symptoms from these conditions like abdominal pain and nausea improve, the diet is usually advanced to a clear liquid diet followed by a low-fat solid diet or bland diet.

Additional reasons why an NPO diet may be recommended include an intestinal blockage, certain traumas, and some instances of bleeding of the digestive tract.

You usually don’t receive any nutrition when you’re placed NPO, but you may receive alternative forms of nutrition through a feeding tube or by vein — known as parenteral nutrition.


NPO stands for nil per os, a Latin phrase that translates to nothing by mouth. Doctors commonly prescribe an NPO diet around surgeries and to manage abdominal pain from inflammatory digestive conditions, among other reasons.

Harms of an NPO diet

Unless you receive tube feeding or parenteral nutrition, an NPO diet eliminates any form of nutrition.

This is less of an issue if you are placed NPO in an outpatient setting — like before a colonoscopy — and more of an issue if you stay in a hospital while under treatment (inpatient).

In these instances, no nutrition — even for a day or two — can significantly increase your risk of malnutrition and infections and increase your hospital length of stay (2, 3).

This is aside from the irritability, headaches, and dehydration that being made NPO for a prolonged time can bring.

Therefore, it’s essential that NPO diets are only prescribed when and for as long as necessary.

Unfortunately, this isn’t always the case.

For example, one study at a university hospital found that more than 40% of all NPO orders were prescribed inappropriately, and 22% of patients were made NPO for a prolonged period of time (five days or longer) (2).

These findings are similar to another study, which showed that 44% of patients with ulcerative colitis at various hospitals were placed NPO inappropriately (4).

Fortunately, many hospitals trigger a dietitian consult for patients who have been placed NPO or who has been NPO for 24–48 hours.

This trigger prompts dietitians to assess the patient and either recommend advancing the diet or recommend alternate forms of nutrition like tube feeding.


There are many times when an NPO diet is unnecessarily prescribed or prescribed for longer than needed. In the absence of other forms of nutrition like tube feeding, this can increase your risk of malnutrition, increase the hospital length of stay, and cause irritability and dehydration.

NPO after midnight

“NPO after midnight,” is a common order prescribed in anticipation of procedures requiring sedation or general anesthesia.

As the name implies, it means you cannot have any food or beverages after midnight.

Despite being routinely prescribed, NPO after midnight orders leave you without food or drinks for longer than necessary.

To this point, the American Society of Anesthesiologists (ASA) guidelines allow a light meal within 6 hours and clear liquids before a procedure (5).

So if you have a 3 PM procedural time, you could have a light breakfast around 9 AM and clear liquids like broth or a sports drink up until 1 PM.

These guidelines were published in 1998 and remained unchanged in the updated 2017 version (5).

Despite these guidelines, many hospitals continue to recommend NPO after midnight.

While it’s difficult to quantify, it’s frequently stated that it takes hospitals and clinics about 17 years to adopt evidence-based research after it’s published (7).

But in this case, the adoption time is clearly much longer for many hospital systems.

Aside from the increased hunger and tiredness of prolonged NPO, the practice of NPO after midnight eliminated the opportunity to promote faster recovery from surgery.

For example, research suggests that patients who receive a carbohydrate-rich drink two hours before procedures experience decreased length of stay and improvements in post-surgery recovery (6).

But, this doesn’t mean that everyone can safely have a light meal or clear liquids within a few hours of surgery.

If you have gastroparesis — or delayed stomach emptying — or other conditions that put you put you at a greater risk of anesthesia-related aspiration like trauma or pregnancy, you may require a longer NPO duration (8).


Despite the American Society of Anesthesiologists (ASA) guidelines, many patients are placed NPO after midnight, eliminating the opportunity to enhance post-surgery recovery and patient satisfaction.

The bottom line

Being placed NPO means that you cannot have anything to eat or drink — including water — for a certain period of time.

An NPO diet is commonly prescribed around surgeries to reduce the risk of anesthesia-related aspiration and to manage symptoms like nausea and vomiting related to inflammatory digestive conditions, among other reasons.

While necessary in some instances, the NPO diet tends to be overprescribed and prescribed for longer than necessary, increasing the risk of adverse health outcomes while decreasing patient satisfaction.

The antiquated practice of NPO after midnight leaves patients without food or drinks for longer than necessary.

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