Why You Can't Eat or Drink Before Surgery

Person pouring a glass of water from a water bottle.

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Eating or drinking too close to surgery involving general anesthesia may result in your surgery being postponed. This is because undigested food in your digestive tract can cause complications like vomiting and aspiration, when food comes up into the esophagus and lungs.

Fasting is also typically required before procedures that use regional anesthesia (like an epidural) or IV sedation. However, you generally do not need to fast before local anesthesia or nitrous oxide (laughing gas).

This article explains how long you should fast prior to surgery, according to the latest guidelines. It also discusses why you can't eat or drink before surgery and offers suggestions for what to eat before beginning your fast.

What Happens If You Eat Before Surgery?

Having food in your stomach when you're given general anesthesia can cause serious problems, including nausea, vomiting, and aspiration. It can also cause complications for surgeries involving your digestive system.

why you can't eat or drink before surgery

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Aspiration is when something you eat or drink goes down your airway. If this happens while you're awake, your body reacts. You may cough, gag, or even vomit. Eventually, you will get the substance out of your airway.

Under general anesthesia, you can't react to aspiration. This is because you are unconscious, and your muscles are paralyzed. You aren't able to cough anything up.

You will also have a tube called an endotracheal tube in your throat. This tube helps you breathe but can make it easier to aspirate. It can also make it harder for medical staff to realize what is happening.

Aspiration can lead to aspiration pneumonia. This is a lung infection caused by inhaling foreign material.

Aspiration is most common during general anesthesia. However, it can also happen when a patient is sedated or too sick to protect their airway.

Nausea and Vomiting

Postoperative nausea and vomiting (PONV) is one of the most common complications of surgery. It is much easier to prevent than to treat and control after it starts.

You can avoid PONV if your stomach is empty when under anesthesia. Medication can control nausea and vomiting, but it is far better to stop it from happening in the first place by adhering to your surgeon's recommendations for fasting before surgery.

Your Bowel Prep Will Be Ruined

If there is food in your gastrointestinal (GI) system during GI surgery, it could complicate the surgery and lead to infection. If you eat or drink before GI surgery, your surgery may be canceled or rescheduled.

In some cases, bowel preparation is done before GI surgery. If you eat or drink after bowel preparation, it will undo everything you've done to empty your GI tract.

Guidelines for Fasting Prior to Surgery

Pre-operative fasting is required prior to general anesthesia, regional anesthesia, and IV sedation. You typically do not need to fast before local anesthesia or nitrous oxide.

How long you need to fast prior to surgery has changed over the years. The current guidelines allow you to eat a light meal for up to six hours and drink clear liquids up to two hours before surgery. However, some procedures may have different requirements. Always follow your healthcare provider's instructions for fasting prior to surgery.

In 2017, the American Society of Anesthesiologists (ASA) revised its practice guidelines for the preoperative fasting timeline for healthy adults who are not undergoing bowel surgery. Additional updates were published in February 2023. The new guidelines differentiate between different types of food and beverages. 

The current recommendations are for healthy individuals undergoing elective (not emergency) procedures. Here's when you need to stop eating and drinking specific foods and beverages prior to surgery: 

  • 8 hours or more: Stop eating fried or fatty foods and meat because they can delay gastric emptying time. 
  • 6 hours: Prior to this point, you should eat a light meal or snack (one that does not include fat or protein), such as unbuttered toast or crackers. Milk and infant formula may also be consumed up until six hours before surgery. 
  • 4 hours: Breastfeeding infants or toddlers should have their last feed up to four hours before surgery. 
  • 2 hours: You can drink clear liquids up to two hours before surgery. This includes water, fruit juice without pulp, carbonated beverages, black coffee, or clear tea without milk. 

The 2023 updated recommendations also encourage children and allow healthy adults to drink between 300 mL to 400 mL (10 to 13.5 ounces) of a carbohydrate-containing clear beverage just prior to two hours before the scheduled surgery. 

These recommendations apply only to healthy patients undergoing elective procedures that do not require a bowel prep. They are not intended for pregnant people in labor, emergency procedures, or those with conditions that increase the risk of aspiration.

People with esophageal disorders such as significant uncontrolled reflux disease, hiatal hernia, Zenker’s diverticulum, achalasia, stricture, previous gastric surgeries (like gastric bypass), gastroparesis, diabetes, opioid use, gastrointestinal obstruction, or obesity are advised to fast longer.

Always follow your surgical team's recommendations for how long to fast before surgery.

Can I Chew Gum Before Surgery?

The 2023 updates to the ASA guidelines allow gum chewing up to surgery time, provided you do not have any contraindications. Research shows the risk of complications from chewing gum is slim. What's more, studies show chewing gum can help to relieve pre-surgical anxiety.

Previously, chewing gum was considered on par with non-clear liquids and not allowed before surgery. Delaying surgery due to chewing gum is no longer required. Patients are reminded to remove gum prior to receiving any sedation.

What to Eat Leading Up to Surgery

If you are several days or weeks from surgery, try to eat more lean, protein-rich foods, which can help you heal after surgery. Examples include:

  • Pork
  • Chicken
  • Seafood
  • Tofu/beans
  • Low-fat dairy products

Hydrate, preferably with water. Your urine should be clear and mostly colorless. Taking these steps in the days before surgery can help sustain you through the fasting period. If you are well hydrated before you fast, you may feel less thirsty during your fast.

Your Last Meal Before Surgery

You may be tempted to have a huge meal before you start your fast. Unfortunately, this could defeat the purpose of fasting.

Instead, have a light meal like soup and salad. A heavy meal takes longer to digest. The current guidelines recommend not eating fried, fatty, or protein-rich foods for at least eight hours prior to surgery. People who have delayed gastric emptying may need to avoid fat and protein for longer.

For most people, a light, low-fat meal can be eaten up to six hours before surgery. This can include toast or crackers with juice or coffee or a small bowl of cereal with milk. After this, adults can drink clear fluids up until two hours before surgery.

Be sure to follow your surgeon's instructions for fasting and be completely honest with the anesthesiologist about when and what you last ate and drank.

Diabetes and Fasting for Surgery

Fasting may cause problems for people with diabetes. If you are on an insulin pump, you may need to lower your basal rates or suspend insulin delivery during the fasting period.

Ask your surgeon in advance how you should handle hypoglycemia during presurgical fasting In most cases, you should be able to treat low blood sugar with clear, pulp-free juice or non-diet soda up to two hours before your scheduled procedure.

Medications During Pre-Surgical Fasting

Check with your surgical team regarding whether or not to take your regular medications on the morning of your surgery. If so, plan to take pills with the smallest sip of water possible. Do not take your medication if the surgeon does not say you should.

If you are unsure, call the surgeon's office to ask or bring the medications with you to the surgical center.


Fasting before surgery helps prevent complications. This includes nausea, vomiting, and aspiration—when you inhale food or fluids that were in your stomach. Aspiration can lead to a serious lung infection.

In the days before your pre-surgical fast, eat lean proteins and stay hydrated. If a bowel prep is needed before your procedure, follow your surgeon's instructions for fasting. Eating or drinking too close to surgery will undo the bowel prep.

Unless otherwise advised, avoid eating fatty, fried, or protein-rich foods for at least eight hours before surgery. You can have a light meal up to six hours before surgery. This includes soup, salad, toast, crackers, or a bowl of cereal. Clear liquids are typically allowed up to two hours before surgery.

If you have diabetes, ask your surgeon how to manage low blood sugar while fasting. Clear liquids may be allowed up to two hours before surgery. Likewise, if you take any daily medications, seek guidance from your healthcare team.

Follow your surgical team's recommendations for fasting prior to surgery. Be completely honest with the anesthesiologist regarding what you ate and when in the hours before surgery.

A Word From Verywell

It seems simple: Fasting before surgery prevents problems. However, an amazing number of patients do not follow these instructions.

The risks of eating and drinking before surgery are higher than you may think. It is important to be honest with your surgical team about anything you ate or drank in the hours before anesthesia. Not disclosing this information may put you at risk for aspiration pneumonia or other serious complications.

By Jennifer Whitlock, RN, MSN, FN
Jennifer Whitlock, RN, MSN, FNP-C, is a board-certified family nurse practitioner. She has experience in primary care and hospital medicine.