Why can't I eat or drink before and after the surgery?

Last updated date: 07-Aug-2022


15 mins read

Why I can’t eat or drink before and after the surgery?

It is a hard part of every surgery. Having a sip of water or a little bite of food is a huge temptation. You can ask yourself: Do I really have to starve? The answer is cruel. Yes, you have to. And we will explain why.

Many people have heard that they should refrain from food and water before surgery. If you do not fast before surgery, the contents of your stomach can flow back to the lungs when you induce anesthesia, which can cause airway obstruction or serious infections like pneumonia. Therefore, it is recommended that the fasting period be observed when you’re scheduled for sleep or general anesthesia. (Normally 6 hours is recommended.)


But should I fast after my surgery?

Yes, you should not drink water or eat food right after surgery.

Why is that?

After anesthesia, the body’s organs are also anesthetized and fail to function properly. Immediately after surgery, you should be careful with the food or even a sip of water because of the remaining anesthetic energy.

Each anesthesia varies, but some people may feel unwell or vomiting and feel dizzy, so you should drink a small amount of lukewarm water first (around 1-2 hours after surgery), and if you have no problems, you can have some light meals. Eating immediately after surgery can cause vomiting, nausea, and abdominal pain.

Although there may be a difference in fasting periods, of course, light local anesthesia does not require fasting. If you have undergone surgery under general anesthesia, you should be more careful. You may be thirsty and hungry by starvation, but you must keep it for safe surgical results.

That was a quick overview to answer your question about why patients are not allowed to eat before surgeries.

But let me explain to you in a more detailed scale the answer to this question.


So, why can't you eat or drink before surgery? 

We don't want to overstate it, but it is not as simple as it seems.

The decision of not eating or drinking before surgery is branched to include many factors. 

These factors can directly affect many decisions regarding surgical operations.

Every operation is different, and whether you can eat or drink the surgery or what you can eat will depend on two important factors: the type of the surgical operation and the type of anesthesia you will have.


Let's start with anesthesia

Anesthesia is considered a type of treatment that uses drugs called anesthetics. These drugs are highly capable of masking pain during different medical procedures. Doctors who administer anesthetics and manage pain are called anesthesiologists. Some types of anesthesia affect a small area of the body and numb it, while other types make you unconscious during invasive surgical procedures, they numb the brain itself and induce sleep.

If you know how anesthetics work, you will understand the mechanism that numbs the pain and makes the brain unconscious.

Anesthetics usually work by temporarily blocking sensory, especially pain, signals from the peripheral nerves to pain centers in the brain. Those peripheral nerves connect the central nervous system with the rest of the body. They carry different signals such as pain, touch and temperature from different body areas to the brain.


So, what are the types of anesthesia? 

Types of anesthesia include: 

  • Local anesthesia. This is the type that numbs a small area of the body. This type is usually used in minor or simple procedures such as cataract, tooth extraction or skin biopsy. Local anesthetics don't numb the brain so you are awake during the procedure. In conclusion, they are generally safer and don't normally require any special preparations before they are used and patients recover from them more quickly.
  • Regional anesthesia. This type blocks the pain in a larger area of the body such as numbing a limb or the whole area below the chest. Patients can be conscious during the procedure or they can be sedated. A very common example of this type is epidural anesthesia. It is used to ease the pain of childbirth during a C-section. There is also spinal anesthesia, a type of regional anesthesia that is used in hip or knee surgeries. Another common type is arm block which is used in hand surgeries.
  • General anesthesia. You might have figured by now that this is the type that numbs the brain and induces sleep. It makes patients unconscious and insensitive to pain or other sensations. It is used in invasive surgeries such as head or abdomen surgeries.
  • Sedation. We just mentioned this word earlier. Sedation relaxes the body to the point that patients will have a more natural sleep. Although it induces natural sleep, patients can be easily aroused or awakened. Sometimes it is used with regional anesthesia. Besides, it can also be used in procedures that require light or moderate sedation such as cardiac catheterization and some colonoscopies. Sedation should be provided by an anesthesia professional because breathing may be affected. Although sedated patients are not completely unconscious, patients are not as likely to remember the procedure.

The type of anesthesia your healthcare provider uses and how it is administered is depending on the type and scope of the procedure.

For example, you may have seen a surgical procedure in a movie, and you saw the patient inhaling through a mask before he or she went unconscious. 

From this scene, you can deduce that anesthesia can be delivered via inhalation. In addition to inhalation, it can also be delivered via injections including shots or intravenously. 

And other ways of administration include topical application such as applying liquids, sprays or patches on the skin.

This is all you need to know about anesthesia.


So, back to our main topic. How is this information related to eating before surgeries? 

Well let's rephrase that question to a more accurate form and it is: 

Can we eat before local anesthesia? Or general anesthesia? 

eat before local anesthesia

Before any surgery, the healthcare professional that is treating you will give you some instructions about: 

  • Whether you can eat or drink.
  • What foods or liquids you can have if eating and drinking are allowed?
  • When to stop eating and drinking.

If you or someone you know have gone through surgery, you will be aware of the type of instructions doctors usually give before major surgeries.

And as you know, one of the most important instructions before surgeries is fasting.

But does that apply to all types of procedures? 

In fact, no. It doesn't apply to all types of procedures and to prove it for you, let's have a look at that example. In tooth extraction, patients usually receive local anesthesia, but does that mean they shouldn't eat or drink before their procedure? 

If you or someone you know goes through a tooth extraction procedure, you will know quite well that you can eat or drink as you wish before the procedure.

From this example, we can conclude that if you are having a local anesthetic, you will be allowed to eat or drink normally before your procedure.

As for general anesthesia, usually before having a general anesthetic, you will not be allowed anything to eat or drink. 

And doctors don't recommend this only to annoy their patients, of course not. These rules about stopping eating or drinking before surgical procedures were made to keep patients safe.

Patients need to have an empty stomach before any surgery or procedure that requires general anesthesia. 


But why is that? Why can't you eat or drink before surgery? Or to be more specific, why can't you eat or drink before a surgery that requires general anesthesia? 

It is very important to have an empty stomach before surgeries for the following reasons:

  • To prevent nausea.
  • To prevent foods or liquids from getting into the lung.

In the first part of our article, we gave you a quick review of what happens when you eat before surgery.

But now, let's take a deeper dive into that subject.


Let's start by asking some questions.

1. First, why can you not eat before surgery? 

This is mainly because when an anesthetic is used, the body's reflexes are temporarily stopped. 


2. But what if you are having a procedure on your shoulder, why does it matter what's in your stomach?

Regardless of the type or the site of your procedure, the stomach should always be empty before having anesthesia. Because, as we explained, anesthesia reduces the body's reflexes, which is the body's ability to protect itself and prevent food and acid from the stomach from entering the lungs.

Normally, your body can do this very well but anesthesia makes it harder for your body to do so.


3. And what about drinks? Why can't you drink before surgery?

The same rules apply to drinks.  

When you are planning to have surgery, you are told that you shouldn't eat or drink 8 to 12 hours before the surgery.

Unless it is okay to take your medications the morning before surgery with a few sips of water.

But when doctors say no food or drinks, they mean it.

It means absolutely no food or drinks, not even snacks or sips of water.

The good news is, since many surgeries are scheduled in the early morning, many people sleep through most of the 8 or 12 hours. Patients usually stop eating around dinner time the night before the surgery and don't take anything by mouth when they wake up and until the surgery is over.

In some special cases, bowel preparations are needed. It is a process that is used to remove food or stool from the digestive tract.

But oftentimes, most patients can just avoid eating food after dinner time. 


4. So, what if someone ate before their surgery? What happens if you eat before surgery? 

Some people can't abide by rules. But this is serious, if you eat or drink before your surgery, your surgery can be postponed or canceled.

There are multiple reasons why patients are asked to stop eating or drinking before their surgeries, some of which are potentially serious and fatal.

If you can't imagine how serious this is, let's have a look at the complications caused by having food in the stomach while administering anesthesia.


Let's start with aspiration. What does it really mean?

Have you ever taken a bite of something or drunk a sip of water or juice and had it go down the wrong pipe?

This is exactly the meaning of aspiration. It can happen with saliva or the food or drink you have.

But you have to note that aspiration is different from choking in that the airway is not completely blocked. Air still flows in and out of the lungs.

When aspiration happens when you are awake, you cough, gag or maybe even vomit until you get that particle out of your airway.

However, under general anesthesia, the body's ability to react is temporarily stopped because the muscles are paralyzed and the brain is unconscious. That's why under general anesthesia you can't cough the aspirated things up. Add to this the endotracheal tube that is usually inserted in the throat during surgeries. This tube makes it so easy to aspirate and so hard for the staff to notice what's happening.

Aspiration is very common with general anesthesia; however, it can also occur if the patient is sedated or too sick to protect their airway.

You might ask, why are we so concerned with aspiration? 

That's because it has serious outcomes.

The main concern of aspiration is the development of lung infection, a condition known as aspiration pneumonia. In most cases, aspiration pneumonia is the result of bacterial infection.

How does this infection happen? It is quite simple. When a foreign substance is aspirated into the lungs, bacteria that are not commonly found in the lungs can be carried along. Even if saliva is aspirated, it carries some types of bacteria.

If you are a surgeon, how would you suspect aspiration pneumonia? 

Aspiration pneumonia usually has a set of symptoms, including: 

  • Shortness of breath.
  • Chest pain.
  • Wheezing.
  • Cough, possibly with blood or greenish sputum.
  • Fever.
  • Fatigue.
  • Weakness.
  • Profuse sweating.
  • Bad breath.

That was the first and the most common complication of eating before surgeries.


The second one is ruining bowel preparations.

When the surgery is intended to be in the gastrointestinal system, having food in the system will complicate the procedure and lead to infection.

When a patient eats after bowel preparation, it undoes all the efforts to empty the digestive tract.

Eating in this case literally will ruin the doctors' work.


The next complication we are talking about is nausea and vomiting. 

One of the most common complications of surgeries is postoperative nausea and vomiting.

Of course, some medications can treat nausea and vomiting, but in this case, it is far easier to prevent it than to treat it or control it after it begins. And therefore, the easiest way to prevent it is to have an empty stomach before the procedure and before anesthesia is administered.

And, as we mentioned before, vomiting is not only limited to after surgeries, but it can also occur during surgeries while the patient is under anesthesia. 

And you can conclude here that in this case aspiration will inevitably occur.

And it is the natural result, to be honest because patients are asleep and paralyzed. The ability to cough or even spit the vomit out of their mouths is taken away from them. And as a result, aspiration risk is quite high. 

Therefore, the best way to prevent this from happening is to ensure patients don't eat or drink before surgeries.


And here comes the urgent question that I know you have in your mind right now.

5. How long can you eat before surgery? 

Well, it depends.

The amount of time you can eat or drink before surgery depends on the type of operation you are having.

But let us ask the question in a more specific way.

How many hours can you eat before the surgery?

If you are having surgery, you can eat the day before as you want. However, it is common for doctors and surgeons to advise patients not to eat or drink at least eight hours before the surgery and sometimes up to 12 hours.

Some doctors say that patients should stop the food at least six hours and stop fluids at least two hours before the surgery.

And when we say stop eating, it means cutting off all types of food even chewing gum is prohibited.

Doctors also recommend avoiding certain types of fluids such as milk or tea and coffee with milk added to them before the operation. Because if it happened and the patient vomited during the surgery after having these drinks, the liquid could easily damage the lung if it got into it.

That's why clear fluids such as water are always recommended.

But that wouldn't apply to infants because if an infant is having an operation, it can be given breast milk up to 4 hours before the operation and after that time, only clear fluids are allowed.

But this rule can be changed according to the health condition of the patient. For example, if a patient has diabetes, that means he or she needs to eat and drink regularly. In this case, the patient will tell the healthcare professional and hence a suitable management plan will be made.

We just mentioned fluids that you can't drink before surgery such as tea or coffee with milk. 


6. So, what can you eat before surgery? 

what can you eat before surgery?

This is actually a smart question. In the hours in which eating is allowed, what types of food can you have? 

You might be tempted to have a huge meal before you start your eight-to twelve-hour fast.

But this is not right. Don't give in to that temptation because it completely defeats the purpose of fasting.

Instead, a healthy balanced diet should be maintained for a few days before the surgery.

Smoking also should be stopped at least ten days before the surgery and alcohol consumption should be reduced or removed entirely at least 24 hours before the surgery. 

That's very helpful, but again, what can you eat before surgery? What types of food are allowed? 

Ideally, the pre-surgical diet should consist of: 

  • Fruits and vegetables. They are easily digested which helps to maintain the weight in the postoperative period when the body needs rest. Fruits and vegetables are also very rich in vitamin C, which promotes collagen formation and, consequently, promotes healing and speed recovery.
  • Slow carbohydrates such as rice or pasta. They significantly improve digestion. This is very helpful and important before acute medical interventions. On the other hand, fast carbohydrates are well-absorbed, improve mood, and activate the production of serotonin; however, their absorption can be slowed down by a lack of motor activity and exercise.
  • Unsaturated fats. In surgery preparations, fats must be unsaturated to be useful to the can be found in olive oil, avocado, oily fish and nuts.

So, a light meal such as soup and salad as your final meal before surgery would be very beneficial.

But again, this is the general rule and it can be changed according to every patient's situation.


So, let's take some examples. Let's have a look at different types of surgeries.

And let's start with oral surgeries.

Why can't you eat or drink before an oral surgery? 

In most oral surgery’s patients are sedated. So, if you are going to be sedated during your oral surgery, you shouldn't eat or drink anything, including water, after midnight to reduce the risk of aspiration. Although it is a rare complication, it is better to be cautious.


Let's have another example, gallbladder surgery for instance. 

Can you eat before gallbladder surgery?

In fact, no, you can't eat before your gallbladder surgery.

One of the most important rules your surgeon tells you before cholecystectomy is: eat nothing the night before your surgery. 

You may, as we elaborated before, take a sip of water with your medications but eating and drinking should be avoided at least four hours before the surgery.

This is not the case with all the surgeries as we mentioned before.


Let's look at LASIK surgeries.

Can you eat before Lasik surgery?

Unlike most surgeries, you can eat before Lasik. 

However, you don't want to get overly full. You might enjoy a light snack to ensure Comfort during your procedure.


Do you know what other surgeries you can eat before them? Have you ever heard about Mohs surgery? 

It is a precise surgical technique to treat skin cancer.

So, can you eat before Mohs surgery? 

Yes, you can. Unlike other surgeries, Mohs surgery uses local anesthesia and that's why you are allowed and encouraged to eat your breakfast the morning of the surgery.


What about other surgeries? Can you eat before hernia surgery? 

As for hernias, patients can't eat anything after midnight the night before surgery. 


Knee surgeries are quite common these days. So, what should you avoid before knee surgery? 

Along with stopping food the night before the surgery, it is also recommended that patients stop:

  • All NSAIDS seven days before the surgery because they interfere with blood clotting.
  • Blood thinners.
  • Most supplements like vitamin E, fish oil and glucosamine seven days before the surgery.


Another important question we get is about herbs and their relation to surgeries.

Let's take garlic and garlic supplements as an example.

Why can you not eat garlic before surgery?

Garlic supplements are used to lower blood pressure and cholesterol. So, garlic can increase the effects of blood sugar or blood thinner medications. It can also increase bleeding during or after surgery. That's why it is better to be avoided.


Surgeries are no fun, and no one will undergo surgery if there is another available option for them. So, if you are about to undergo surgery, always follow your surgeon's instructions to be safe.


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