Version July 2025
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What is fasting? —
This is not eating or drinking anything for a period of time. People sometimes need to fast before getting a medical test, procedure, or surgery.
Do I need to fast before my surgery? —
Maybe. It depends on what kind of surgery you are having, and what kind of anesthesia you will get. "Anesthesia" means different types of medicine given during surgery or another procedure. These medicines make sure you do not feel pain during surgery.
If you have a scheduled surgery or procedure, your doctor or nurse will tell you if you need to fast before it. If you are only getting "local anesthesia," you probably will not need to fast. Local anesthesia is medicine to numb a small part of your body. It can be given as a shot, or as a cream, gel, or spray that goes on your skin.
You will need to fast if you are getting any of these:
●General anesthesia – This makes you unconscious so you can't feel, see, or hear anything during surgery. Some of the medicines are given through a thin tube that goes into a vein, called an "IV." Others are gases you breathe in.
●Regional anesthesia – This blocks pain in 1 area of your body, such as an arm, a leg, or the lower half of your body. The doctor will inject medicine around the nerves that go to the area where you are getting surgery.
●Sedation – This means getting medicines to make you relax and feel sleepy.
Why do I need to fast? —
You need to fast to make sure your stomach is as empty as possible when you get anesthesia. If you have food or liquid in your stomach, some of it could get into your lungs while you are under anesthesia. This is called "aspiration." Normally, your body can prevent this from happening. But anesthesia medicines make it harder for your body to prevent it.
Aspiration is rare, but can be dangerous. That's because it can lead to infection, lung damage, or breathing problems.
How long before my surgery do I have to stop eating and drinking? —
It depends. Your doctor or nurse will give you instructions for your situation.
An example might be:
●Do not eat any solid foods for 6 to 8 hours before surgery. You should also avoid drinking milk after this time, because milk "curdles" into small solid bits in the stomach.
●You can drink clear liquids up to 2 hours before surgery. Clear liquids include water, juice with no pulp, and coffee or tea without milk or cream.
●Do not eat or drink anything, even clear liquids, during the 2 hours before surgery. But if you are told to take a medicine during this time, you can take it with a sip of water.
Your hospital or clinic might have slightly different rules. For example, you might need to:
●Fast for longer after a meal that has a lot of meat or fat
●Fast for longer if you take a medicine or have a condition that slows digestion
There are also special rules for babies and young children who need surgery. For example:
●Most hospitals say you can give breast milk up to 3 or 4 hours before surgery. If your baby drinks formula, you might have to stop giving it sooner.
●Many hospitals let children have clear liquids up to 1 hour before surgery. Your child's doctor or nurse can tell you exactly what to do.
The most important thing is to follow the doctor's or nurse's instructions.
Should I keep taking my medicines before surgery? —
It depends. Your doctor or nurse will tell you which medicines you should take and when. Some medicines need to be stopped before surgery. But for others, it's important you keep taking them as usual. You might also get new medicines to take before surgery.
Take the medicines exactly as instructed. If you need to take medicine before surgery, you can take it with a sip of water. If you normally take your medicine with something else, like applesauce, talk to your doctor or nurse about what to do.
What happens if I don't fast? —
If you don't follow instructions about when to stop eating and drinking, you could be putting your health at risk. Be honest with your doctor or nurse if you did not follow the rules, even if it was an accident. If this happens, your surgery might need to be delayed until a later time.
Patient education: Anesthesia in adults (The Basics)
Patient education: Anesthesia in children (The Basics)
Patient education: Sedation for procedures in adults (The Basics)
Patient education: Sedation for procedures in children (The Basics)
Patient education: Aspiration pneumonia (The Basics)
Patient education: Clear liquid diet (The Basics)
Patient education: Full liquid diet (The Basics)
Patient education: Questions to ask if you are having surgery or a procedure (The Basics)
