Medical Oncologist
CION Cancer Clinics
What should you do the night before your operation? | CION Cancer Clinics
The night before cancer surgery, follow your hospital's fasting times exactly. Food usually stops about six hours before a general anaesthetic and clear fluids about two hours before, but your own sheet comes first. Take only the medicines your team has told you to. This page explains why fasting matters, what counts as food, how the evening should go, and what to do if you ate by mistake. CION Cancer Clinics’ surgical oncologists in Hyderabad can talk this through with you.
MI
Medically reviewed by Dr. Mohammed ImaduddinConsultant Surgical Oncologist · MBBS, MS (General Surgery), MCh (Surgical Oncology) · last reviewed September 2026, next review due September 2027
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On this page
- What should you do the night before your operation?
- What counts as breaking your fast?
- How should the night before usually go?
- Which words might you see on the fasting sheet?
- What do people believe about fasting, and what is true?
- What about diabetes, blood thinners and your regular medicines?
- Common questions about the night before surgery
The short answer
What should you do the night before your operation?
Follow the exact fasting time your hospital gives you. For a general anaesthetic, you are usually asked to stop food about six hours before and clear fluids about two hours before, then take only the medicines your team has told you to take.
Why an empty stomach matters
Anaesthesia relaxes the muscles that normally stop food coming back up from the stomach. It also switches off your cough. If there is food or milk in your stomach, it can travel up and into your lungs while you are asleep. That can cause a serious chest infection. Fasting keeps the stomach empty enough for this to be very unlikely.
Why longer is not better
Many families think fasting from the previous afternoon is safer. It is not. Long fasting leaves you thirsty, dizzy and dehydrated, can make veins hard to find, and can upset blood sugar. Stop at the time you are given, not hours earlier.
Who this pattern does not suit
People with diabetes, people having bowel preparation, children, and anyone on a special feeding plan may get different instructions. Some operations also need a longer fast. Your own hospital's sheet always comes first.
Food, drink and habits
What counts as breaking your fast?
Families are often unsure about tea, water and paan. This is what usually counts, but check your own instructions.
Food and milky drinks
Any food, however small, stops at the food cut-off time. Milk, tea or coffee with milk, lassi, buttermilk, juice with pulp and soup count as food.
Often forgotten
- Biscuits with tea
- Sweets and chocolates
- Prasad on the way to hospital
Clear fluids
Plain water, and sometimes black tea or coffee with no milk, or clear juice with no pulp. These are usually allowed until the clear-fluid cut-off.
Coconut water and ORS are not always counted as clear. Ask.Chewing and mouth habits
Paan, gutka, supari, chewing tobacco and gum all bring saliva and juices into the stomach. Stop them with food, unless your team says otherwise.
Smoking and alcohol
Do not smoke on the night before or the morning of surgery. It affects your breathing under anaesthesia. Do not drink alcohol the day before.
Not sure whether this applies to you?
Ask an oncologistThe evening, step by step
How should the night before usually go?
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Early evening
Re-read the hospital's instruction sheet together. Write the food and fluid cut-off times on paper and tell everyone at home, so nobody offers tea or food by mistake in the morning.
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A light dinner
Eat a normal, light meal before the food cut-off. Avoid heavy, oily or very spicy food. Do not eat extra to "store up" for the fast.
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Bath and skin care
Bathe as your hospital advises. Remove nail polish, make-up and jewellery. Do not shave the operation area yourself unless told to.
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Medicines
Take or leave medicines exactly as your team wrote down. If the list is unclear, call the hospital rather than guessing.
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Sleep
Set an alarm, keep your bag and documents by the door, and try to rest. Feeling anxious and sleeping badly is very normal.
On your instruction sheet
Which words might you see on the fasting sheet?
- NPO or nil by mouth
- Nothing to eat or drink from a stated time. Ask whether this includes water and your morning medicines.
- Clear fluids
- Liquids you can see through, with no milk or pulp, such as plain water.
- Aspiration
- Stomach contents going into the lungs during anaesthesia. It is the main reason for fasting.
- Carbohydrate drink
- A sugary clear drink some hospitals give before surgery to help recovery. Take it only if your team gives it to you.
- Premedication
- Medicine given before the operation, for example for anxiety or acidity.
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Commonly believed
What do people believe about fasting, and what is true?
"A sip of water to take tablets will cancel the operation."
A small sip of water with the medicines your team told you to take is usually allowed. Check your sheet. What causes delays is food, milk or tea taken after the cut-off.
"It is safer to stop all medicines the night before."
Stopping some medicines, such as blood pressure or seizure tablets, can itself be risky. Others, such as some diabetes tablets or blood thinners, may need to be paused. Only your team can say which. Never stop or change a medicine on your own.
"If I am fasting for a religious reason anyway, it makes no difference."
A religious fast may not follow the same times, and a fast that ends in a large meal the night before can matter. Tell the team about your fast so they can plan around it.
"Nobody will know if I have a small cup of tea."
This is not about rules. Milk in the stomach is a real risk under anaesthesia. If you did have something, say so honestly. The team would much rather delay than take that risk.
!
If you ate or drank by mistake, or feel unwell
Call the hospital as soon as you realise, or tell the nurse the moment you arrive. Say exactly what you had and at what time. Do the same if you develop a fever, cough, loose motions or vomiting the night before. Do not hide it to avoid a delay. Your operation may be moved later in the day, and that is far safer than going ahead.
Being straight with you
What about diabetes, blood thinners and your regular medicines?
These need a written plan from your own team before the night before. If you do not have one, call the hospital that day. This page cannot replace that plan.
If you have diabetes
Fasting can make your sugar drop too low, especially if you take insulin or tablets such as glimepiride or gliclazide. Metformin and some newer diabetes tablets may also need a change. Your anaesthetist or physician will tell you what to take and when. Check your sugar if you have a meter, and tell the nurse if you feel shaky, sweaty or confused.
If you take blood thinners
Aspirin, clopidogrel, warfarin and newer blood thinners affect bleeding. The timing of any pause is decided by your surgeon and the doctor who prescribed them. Do not stop them on your own.
What this page cannot tell you
It cannot tell you your fasting times, which medicines to take, or whether your operation is first or later in the day. Those come from your own hospital, and they can differ from what a friend was told.
Questions we are asked
Common questions about the night before surgery
What time should I stop eating before surgery?
Follow the time your hospital gives you. For a general anaesthetic, food is usually stopped about six hours before the operation, and clear fluids about two hours before. Some operations and some patients need a different plan. If your sheet does not give a clear time, call the hospital the day before.
Can I drink water on the morning of surgery?
Often yes, until the clear-fluid cut-off time on your instructions. Plain water is the safest choice. Do not add milk, juice with pulp or anything cloudy. If you are told "nil by mouth" with no mention of water, ask the hospital whether that includes sips of water with tablets.
Should I take my blood pressure tablets that morning?
Many people are asked to take some blood pressure tablets with a sip of water, and to leave others out. It depends on the tablet. Your anaesthetist or physician will tell you which. Do not decide on your own. Bring all your medicines, in their strips, to hospital.
I have diabetes. What should I do about fasting?
You need a specific plan from your team, because fasting can make sugar drop too low. Diabetic patients are often scheduled early in the day. You may be told to change your insulin or tablets. Check your sugar if you can, and tell staff at once if you feel shaky, sweaty or confused.
Can I brush my teeth the morning of surgery?
Yes. Brushing your teeth and rinsing your mouth is fine. Spit the water out rather than swallowing it. Take out removable dentures before leaving for theatre, but bring them with you in a named case so they can be returned when you wake.
What if my operation is delayed and I am very hungry?
Tell the nurse. Operations do sometimes move later in the day. The team may allow clear fluids until a new cut-off, or start a drip to keep you hydrated. Do not eat or drink on your own, even if the wait feels very long, because your turn may come suddenly.
I could not sleep at all. Is that a problem?
It is very common, and it will not usually stop the operation. Do not take a sleeping tablet you have not been prescribed. Tell the anaesthetist if anxiety is severe. They can talk it through with you and may offer something to help you relax before surgery.
Can I chew gum or have paan to calm my nerves?
It is safer not to. Chewing gum, paan, gutka and tobacco increase saliva and stomach juices, and some hospitals treat them like food. Tobacco also affects your breathing under anaesthesia. If you use tobacco daily, tell the team so they can help with cravings on the ward.
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Sources
- NHS — General anaesthesia
- NICE — Perioperative care in adults (NG180)
- American Cancer Society — Cancer surgery
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
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