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What Does "Nil by Mouth" Mean?

By Jennifer Voight
Updated Mar 03, 2024
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Nil By Mouth (NBM) is a medical order that prohibits anyone from giving a patient food, drink, or medications by mouth. This is frequently necessary for several hours prior to surgery requiring general anesthesia, for certain medical conditions, and after some types of surgery. To prevent dehydration, hospital staff will frequently administer fluids through an IV. Other medical conditions may warrant NBM orders, especially when a patient has difficulty or an inability to swallow, has had alcohol poisoning, or when gastrointestinal bleeding or blockage is present. Nil by mouth is the preferred British term, while the United States and other parts of the world use the Latin term nil per os, or NPO.

Prior to receiving general anesthesia, doctors will issue a nil by mouth order to make sure the stomach has time to empty its contents. It can take as long as six hours for food and thicker fluids and up to two hours for water and clear fluids to leave the stomach. Due to the danger of missing oral medication doses, many times oral medications will be allowed during the fasting period. Any danger of aspiration appears minimal because small amounts of water necessary to help the patient swallow medication appear to be safe and clear the stomach quickly.

While under general anesthesia, a patient’s swallow and cough reflexes are suppressed. A fasting period before surgery ensures that if vomiting occurs during surgery, no stomach contents will aspirate into the lungs. If stomach contents are aspirated, a patient can choke or develop pneumonia with dangerous or potentially fatal consequences.

Physicians may order a nil by mouth order for up to 24 hours or longer prior to gastrointestinal surgery. This is not only to allow the stomach to empty, but to empty the entire bowel prior to surgery. After gastrointestinal surgery, the order may remain in place for a period of time to allow the bowel time to rest and heal.

After a nil by mouth order has been lifted, patients will sometimes be limited to clear fluids until the bowel has had time to adjust to the work of digestion again. Once fluids are well tolerated, easily digested foods will be introduced in small amounts. This is to prevent and minimize nausea and vomiting that frequently occur after the stomach has been at rest for several days. Sometimes doctors may order anti-nausea drugs if nausea and vomiting are severe.

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Discussion Comments

By anon268235 — On May 13, 2012

My daughter is already malnourished and dehydrated, has lost 8 stone in the past year, and now weighs only 8 stone due to a bowel disorder, but she is only given 3 supplement drinks 900 calories a day to survive on. She is put on the theatre list and can wait up to five days to go to surgery with only a drip to sustain her.

After two months in hospital, they are slowly starving her to death. In 14 days, two procedures were done, but she was nil by mouth for nine of these days. It is disgraceful. Urine retention was missed twice, once 1350 ml left in her and the second time 990 ml left in her and they wonder why this has affected her mental health. The system needs addressing before they kill my daughter through neglect.

By Sinbad — On Aug 27, 2011

@saraq90 - Sometimes people are given nil by mouth orders because their swallow reflex has been disrupted; which means that fluid and/or food could be going into their lungs.

As a speech language pathologist we do swallow studies. A swallow study is when the patient takes a swallow of barium liquid or food (so that it shows on the x-ray) and you watch if they are swallowing effectively.

You would be surprised by how many people take food or liquid in and it goes straight into their lungs without so much as a cough or throat clear. In fact it is so common it has a term for it, it is called "silent aspiration" (aspiration means taking in a foreign substance into your lungs).

And you often hear of the word aspiration with pneumonia because foreign objects in the lungs can cause pneumonia.

And just as @domido mentioned, it is very difficult to have an order of nil by mouth, so a speech language pathologist does not suggest it to the doctor unless they have strong finding to suggest the patient's food or drink is going to go into their lungs.

By Saraq90 — On Aug 26, 2011

I can only imagine how tough it is to be nil by mouth for a long period of time. I recently had minor surgery and had to stop eating at midnight, had surgery in the morning, and then could eat probably around noon, and that was a bit difficult just because of habit.

I have heard of people being NPO or nil by mouth in the hospital but it had nothing to do with surgery. Why would someone be in the hospital and be nil by mouth but yet not being prepared for surgery or it being after surgery?

By tlcJPC — On Aug 25, 2011

@ Domido- I totally feel your pain.

I’ve also had to be the bearer of bad news to a person with a NBM order and refuse them what their body naturally wants.

What makes it even worse, though, is when some moron comes in with a drink or a snack to chat. I’ve started just stopping people at the door, because that is pure torture for the sick person to have to watch.

I let people know in a nice but firm way that they should eat and drink in the waiting area. Then, when they’ve finished their snack, they can come on down and visit.

The only thing that has upset me even worse than having to be slightly rude to well-meaning people and constantly denying my loved one sustenance was the time that a family member actually consented to give him an entire soda.

I was furious when I found out, because here was my dad (who was already beyond sick) retching his guts up because some irresponsible dimwit decided he knew more than all of the doctors in the hospital.

By Domido — On Aug 24, 2011

When a doctor gives you a nil by mouth order, it is not fun times, my friends. My poor mother has been given this option so many times it’s not even possible to count it on all of my fingers and toes.

Granted, she is not a very healthy lady and has had a bunch of major medical issues over the past decade. But it still seems like every few months she’s in the hospital with a NBM order posted to her door.

And, when this happens, I have to steal myself for going to see her. She is normally on strong pain medications whenever this happens, and so is not exactly all there. She begs and pleads for food and drink, and we have to continuously tell her no.

It is miserable for her, and it is miserable for us.

By lovealot — On Aug 24, 2011

I'm glad that now women in labor are allowed to have something to eat. Back in the days when I went through childbirth, we were only allowed to chew on little pieces of ice. I remember feeling hungry and wish I been able to eat just a little.

So much has been learned about the process of labor. There are such good techniques a couple can practice if they want to experience natural childbirth, including having some snacks. No nil by mouth order needed!

By Bertie68 — On Aug 23, 2011

A nil by mouth order given by a doctor must be followed strictly. Unfortunately, there have been cases where a patient recovering from surgery has been given a little bit of food. Patients inhaled some of the food into the lungs, contracted pneumonia and died.

Hopefully, the doctors and nurses have learned something from these experiences, apologized to the patient's family, and the hospital has implemented ways to prevent this from happening again.

Medical accidents are one thing, but to ignore a proven technique like nil by mouth before and after surgery is not excusable.

By bagley79 — On Aug 22, 2011

When I had emergency surgery for a ruptured appendix I was given a nil by mouth order for several days after the surgery.

I was in the hospital for a week after that surgery to make sure I did not get infection, and could not eat anything until later on in the week.

Even though you can be kept alive by IV's, it is no fun at all. After a few days of recovery, you are starting to get your senses back, and food starts to sound and smell really good.

You also have to begin eating slowly after you have been off food for several days. It takes your body some time to adjust and I still felt weak for a a few days after I was out of the hospital.

By ElizaBennett — On Aug 22, 2011

@SailorJerry - It used to be quite standard for doctors not to allow women to eat and drink during labor for the very reason you mention. Women would be allowed nothing but ice chips and often hooked up to an IV for fluids.

However, C-section by general anesthesia is very rare, and the latest research shows that eating and drinking during labor is very safe. If you want a natural birth, eating and especially drinking are very important. (Most women aren't super keep to eat during labor, but if your wife is hungry and the doc won't allow her to eat, you can always sneak her a granola bar when you're alone in the room.) Refuse the IV and make sure that you have a care provider who's OK with your wife being allowed to consume clear fluids. A little grape juice can go a long way to keeping your energy levels up!

By SailorJerry — On Aug 21, 2011

My wife and I are expecting our first child. We are hoping for a natural unmedicated birth, but I know that emergencies can happen and that there's always the chance a C-section will be necessary, and occasionally they even use general anesthesia.

Does that chance mean that she shouldn't eat or drink during labor?

By popcorn — On Aug 20, 2011

Being put under a nil by mouth order can be a pretty unpleasant experience. I remember having surgery to help with an ulcer that wasn't responding to medication and I couldn't have anything to eat for about a week following the surgery.

Let me tell you, living off an IV feed is great for losing weight but can be pretty miserable. I was so sick the first few days I didn't care about food, but after that I just had the weirdest food cravings. I suppose since I was getting all of my nutrition through the IV it was mostly in my head, but I was pretty sure I was starving.

By MrSmirnov — On Aug 20, 2011

When my mother was in the hospital to have her gallbladder removed the doctor gave the nil by mouth order because she was going to be under general anesthesia. Apparently my mother has some difficulty with anesthesia and the doctor thought it was safest if she didn't eat or drink anything prior to surgery.

My mom was only allowed a little water 24 hours prior to surgery, and at the 12 hour mark she wasn't allowed anything. Instead they hooked her up to an IV. I suppose that if you have trouble with general anesthesia it is better to prepare for the worst.

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