Fasting Before Surgery: What You Can Eat and Drink, and Why Info In-depth
Reviewed by Dr Kieran Hirpara, Specialist Orthopaedic Surgeon Last reviewed
Also on YouTube.
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.
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 seven 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 further than you need for your own treatment decisions. Anaesthesia is worth the extra reading because the two things patients most want reassurance about — nerve damage from a block, and whether being "awake" is safer than being asleep — both have decent numbers attached, and neither answer is the one intuition supplies.
The risk of lasting nerve trouble from a block
Almost everyone having upper-limb surgery is offered a nerve block, and almost everyone asks whether the needle can damage the nerve. It is a fair question, and the honest answer needs a distinction: temporary altered sensation is not rare, and lasting injury is.
A systematic review pooling 12,532 patients examined postoperative neurologic symptoms after regional anaesthesia for upper-extremity surgery, and its central point is methodological but important to you: the aggregate risk looks very different depending on how it is measured. Prospectively assessed randomised trials — where someone actively asks every patient — report far higher rates than retrospective series, where only patients who complain loudly enough get counted [1].
The practical reading: if a study quotes you a very low figure, ask whether anyone went looking. Symptoms that resolve are common enough that they should be described to you as expected rather than as a complication; symptoms that persist are genuinely uncommon.
Awake is not automatically safer
There is a widespread belief, held by patients and not only patients, that avoiding a general anaesthetic must be safer — particularly in older people, and particularly regarding confusion afterwards.
The most direct test of that comes from hip fracture surgery, where the question has been studied at scale because the patients are old and frail. Pooling 3,736 patients, regional anaesthesia did not significantly reduce postoperative delirium or mortality compared with general anaesthesia [2].
That is a genuinely surprising result and it deserves care in interpretation. It does not mean the choice is irrelevant — it means the choice should be made on the specifics of your heart, lungs, airway and the operation planned, rather than on a general belief that one category is safer. Modern general anaesthesia in a fit patient is very safe, and a block is not a free pass.
Where blocks genuinely earn their place
The strongest case for regional anaesthesia is not safety, it is pain. A systematic review of 1,872 patients undergoing surgical repair of proximal humerus fractures concluded that regional anaesthesia is a good option for postoperative analgesia [3] — the first hours after a shoulder operation are the worst, and a block covers precisely that window.
There is also more than one way to do it. For shoulder arthroscopy, a review of 1,382 patients found suprascapular nerve block was not more effective than interscalene block for pain control, but had a more favourable side-effect profile [4]. Interscalene blocks reliably produce a temporarily weak arm and can affect the nerve to the diaphragm, which matters if your breathing is already marginal. Where that is a concern, a different block is not a compromise — it is the better operation-specific choice.
Why fasting is the way it is
Fasting exists for one reason: an anaesthetised airway cannot protect itself, so stomach contents that come up can go down into the lungs. That event is rare and serious, and the fasting rule is the cheap insurance against it.
The common error is treating "nil by mouth" as a competition. Prolonged fasting does not add safety, and arriving dehydrated makes you feel worse, makes cannulation harder and does nothing for your stomach. Clear fluids empty from the stomach quickly, which is why modern guidance permits them much closer to surgery than food. Follow the times you are given rather than the times you assume — and if surgery is delayed, ask, rather than sitting parched on the assumption that more fasting must be better.
References for the advanced reading
- Albaum JM, Abdallah FW, Ahmed MM, Siddiqui U, Brull R. What is the risk of postoperative neurologic symptoms after regional anesthesia in upper extremity surgery? A systematic review and meta-analysis of randomized trials. Clin Orthop Relat Res. 2022;480(12):2374-89.
- Zhou S, Zhang S, Si H, Shen B. Regional versus general anesthesia in older patients for hip fracture surgery: a systematic review and meta-analysis. J Orthop Surg Res. 2023;18(1).
- Iliaens J, Metsemakers W, Coppens S, Hoekstra H, Sermon A, Van de Velde M, et al. Regional anaesthesia for surgical repair of proximal humerus fractures: a systematic review. Arch Orthop Trauma Surg. 2019;139(12):1731-41.
- Kay J, Memon M, Hu T, Simunovic N, Duong A, Paul J, et al. Suprascapular nerve blockade for postoperative pain control after arthroscopic shoulder procedures: a systematic review and meta-analysis. Orthop J Sports Med. 2018;6(12).
