Fasting Before Surgery: What You Can Eat and Drink, and Why Info In-depth
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Video transcript
Before an operation, you will be asked not to eat or drink for a period beforehand, and there is a good reason for it. Anaesthesia relaxes the body, including the muscles that normally keep the stomach contents down. An empty stomach makes your anaesthetic safer, by lowering the small risk of stomach contents reaching the lungs. Your team will give you exact times for when to stop food and clear fluids, and it is important to follow them. If you are ever unsure, it is best to ask, rather than guess. There is more than one way to keep you comfortable during hand and upper limb surgery. A general anaesthetic sends you fully to sleep for the operation. A regional anaesthetic, or nerve block, numbs just the arm, while leaving the rest of you awake. The two are often combined, with a block for post-operative pain relief. Your anaesthetist will talk through the options, and help choose what suits you and your surgery. A common nerve block for arm surgery is the supraclavicular block. Using an ultrasound to see clearly, the anaesthetist places local anaesthetic around the bundle of nerves above the collarbone that supply the whole arm. This makes the arm numb and heavy for the surgery, and keeps it comfortable for many hours afterwards. The heaviness and numbness are completely expected, and they wear off gradually as the block fades. Having good pain relief already in place often means you need less other pain medication afterwards. When the surgery is finished, you are looked after in recovery until you are ready to go home, or to the ward. If you had a block, your arm will stay numb and heavy for a while, so it is important to protect it, and keep it supported in the sling. Take care around hot surfaces and sharp edges, while you cannot feel the arm normally. As the block wears off, sensation and movement return, and this is the time to start your prescribed pain relief, before the numbness has fully gone. With a plan in place, most people find this a smooth and comfortable experience.
Patients › Recovery
Why you must stop eating before an anaesthetic, when you can still sip water, and what can happen if you do not fast. The clear fasting rules that keep your stomach empty and your lungs safe during surgery.
On the day of surgery, two things matter most for your safety: the type of anaesthetic you have, and how strictly you follow the fasting instructions you were given.
Why we ask you to fast
A general anaesthetic relaxes the muscles that normally stop stomach contents from coming back up the throat. If your stomach is full, that material can spill into your lungs while you are unconscious, which is serious. Fasting empties the stomach so this cannot happen.
The standard rules are:
- No food or milk for 6 hours before your scheduled arrival time. This includes lollies, chewing gum, and tea or coffee with milk.
- Clear fluids are allowed up to 2 hours before: water, black tea, black coffee, apple juice, clear cordial. Sip, don't gulp.
- Stop all clear fluids 2 hours before arrival.
If you have your normal blood-pressure or epilepsy tablets in the morning, take them with a small sip of water unless your anaesthetist has told you otherwise. Diabetic medications and blood thinners are different; follow the specific written advice you were given.
Types of anaesthesia we use
Most upper-limb surgery is done under one of three approaches, sometimes combined:
- General anaesthetic: you are fully asleep. The anaesthetist puts you to sleep through a small drip in the back of your hand and looks after you the whole time.
- Regional block: local anaesthetic is injected around the nerves in your neck or armpit, numbing the whole arm for several hours. You may also be sedated so you sleep through the surgery, but you are not on a ventilator.
- Local anaesthetic: small operations (like a trigger-finger release) can often be done with the area numbed and you fully awake, sometimes with light sedation.
Your anaesthetist will discuss the options with you on the day. The choice depends on the operation, your general health, and what you prefer.
What to expect on the day
You'll arrive 1–2 hours before your scheduled theatre time. A nurse will check your fasting, place a drip, and go through a final consent form. The anaesthetist will see you in person before you go to theatre.
After surgery you'll wake up in the recovery area. If you had a regional block, your arm will feel heavy and numb; this is normal and lasts 8–24 hours. Protect a numb arm: keep it in the sling, don't lean on it, and keep it warm. Sensation comes back gradually, often with some pins and needles.
Nausea, drowsiness, and a sore throat (from the breathing tube) are common in the first few hours. Drink slowly, eat lightly, and rest.
Advanced reading: the deeper science (optional)
This section goes a step deeper into why the rules are what they are. It is not needed to follow your fasting instructions, but it explains the physiology behind them.
Why an empty stomach matters: the aspiration risk
When you are awake, reflexes at the top of your gullet keep stomach contents from rising into your throat and windpipe. A general anaesthetic switches those reflexes off. If the stomach still holds food or fluid, it can flow back up and spill into the lungs, a problem called aspiration. Stomach contents are acidic, so this can inflame the lungs and cause a serious chest infection. Fasting empties the stomach so there is little to bring up, and that is the single biggest reason for the rules.
Why six hours for food but two for clear fluids
The stomach handles different things at different speeds. Solid food and milky drinks are broken down slowly, so they need about six hours to clear. Clear fluids such as water, black tea or coffee and clear juice pass through within a couple of hours, which is why a few sips of water are allowed up to two hours before surgery. Current guidance actively encourages clear fluids up to that two-hour point, because going into an operation well hydrated is better than being parched for half a day, and it does not add to the aspiration risk.
How the anaesthetic options work
A general anaesthetic acts on the brain to keep you fully unconscious and unaware for the operation. A regional block works further out along the nerves: local anaesthetic is placed around the bundle of nerves that supplies the arm (in the neck or the armpit), which temporarily blocks the signals travelling along them, so the arm goes numb and heavy and stays pain-free for many hours after you wake. The two are often combined, giving a smooth anaesthetic plus built-in pain relief for the first day.
Call us if
- You are unsure about your medications on the morning of surgery
- You become unwell (cold, fever, stomach bug) in the days before
- You accidentally ate or drank inside the fasting window; tell us at check-in, don't just hope it's fine
