Ask anyone who has had a colonoscopy what the hardest part was, and you will usually get the same answer: the day before. The test itself takes about half an hour, and with sedation many people don't remember much of it. The preparation is the part you do at home, on your own, and it quietly decides how good the test will be.
We see this every week. When the bowel is clean, the doctor gets a clear view of the whole colon, small polyps are easy to spot and the test finishes on time. When it isn't, there is a real chance something gets missed, and some people have to come back and do the whole thing again. Nobody wants that. So here is a plain, day-by-day guide to getting it right.
One request before you start: your clinic will give you written instructions for your own test. Follow those first. This guide explains the reasons behind them, which makes them much easier to stick to. If you have not booked yet, you can read about the colonoscopy test at Medigest.
Why a clean bowel matters so much
A colonoscopy is a look at the inside lining of the large intestine. Early cancers and the polyps that turn into them are often flat, pale and only a few millimetres across. A thin film of stool is enough to hide them. That is why doctors talk about the "quality" of preparation, and why your report will often mention it. A good preparation is not about comfort; it is about not missing anything.
A week before: go through your medicines
This is the step people forget, and it causes the most last-minute cancellations. Sit down with your medicine strip a week ahead and check these:
- Iron tablets. These are usually stopped five to seven days before. Iron turns the stool dark and sticky and makes cleaning harder.
- Blood thinners. Aspirin, clopidogrel, warfarin and the newer blood thinners need a decision from the doctor. Please don't stop them on your own; some are continued and some are paused, depending on why you take them and whether polyps might be removed.
- Diabetes medicines and insulin. On the liquid-diet day you eat very little, so the doses usually need to come down. Ask for a written plan so your sugar doesn't drop.
- Long-standing constipation. If you go two or three days without a motion, tell the clinic. You may need an extra day of preparation.
Two to three days before: switch to low-fibre food
Fibre is good for you on every other day of the year, but before a colonoscopy it leaves bulky residue behind. For two or three days, keep meals simple and soft.
Foods that work well: white rice, moong dal khichdi, plain idli or dosa, white bread, suji upma, curd, paneer, eggs, boiled potato without the skin, and ripe banana. Strained dal water and clear soups are fine too.
Foods to keep away from: anything with small seeds (tomato, cucumber, guava, kiwi, brinjal), leafy vegetables and salads, sprouts, whole wheat atta rotis and multigrain bread, nuts, popcorn, and fruit with the skin on. Seeds are the worst offenders. They don't dissolve, they block the suction channel of the scope, and they slow everything down.
The day before: clear liquids only
From the morning of the day before (or the time your clinic gives you), stop solid food. Clear liquids are anything you could read a newspaper through: water, coconut water, clear soup, strained dal water, lemon water, plain tea or black coffee, clear apple juice, ORS and glucose water. Avoid milk, lassi, and anything red or purple, because coloured drinks can look like blood on the screen.
Drink more than you think you need. People who drink well through the day feel less tired, get fewer headaches and find the prep medicine works faster.
The bowel prep medicine
Most clinics in India use a polyethylene glycol (PEG) solution that you mix in water. You may know it by brand names such as Peglec. Some doctors prescribe a smaller-volume prep instead. Whatever you are given, take that one, exactly as written.
Why we split the dose
The most effective way to take it is a split dose: half the solution the evening before and the other half early on the morning of the test, finishing at least two hours before your appointment (or as instructed). Splitting it gives a cleaner colon than drinking it all the night before, and it is easier on the stomach.
Making it easier to drink
- Chill it in the fridge. Cold solution tastes far less salty.
- Drink one glass every 10 to 15 minutes rather than forcing it down.
- Use a straw placed towards the back of the tongue.
- Suck a slice of lemon or rinse your mouth with water between glasses.
How to tell your bowel is clean
By the end, what you pass should be watery and clear or light yellow, a bit like urine, with no solid bits. If it is still brown or has particles on the morning of the test, call the clinic before you leave home. Sometimes an extra dose solves it; sometimes it is better to reschedule than to do a test with a poor view.
Small problems and what to do about them
Feeling sick. Stop for 30 minutes, take a short walk, then carry on more slowly. Bloating or cramps. These ease once the bowels start moving; walking helps. A sore bottom. Use soft wet wipes and a little petroleum jelly. Dizziness or weakness. Keep sipping ORS and clear fluids. If you vomit repeatedly, can't keep fluids down, feel faint or have severe pain, call the clinic straight away.
On the morning of the test
Take only the medicines your doctor has allowed, with a sip of water. Wear loose clothes, bring your earlier reports and a list of medicines, and if you are having sedation, bring an adult who can take you home. Sedation affects your reactions for the rest of the day, so you should not drive, sign important papers or go back to work.
After the colonoscopy
Once you are fully awake you can usually eat a light meal: khichdi, curd rice or toast is a good start. You may feel bloated and pass a lot of gas for a few hours; that is the air used to open the bowel and it settles on its own. If a polyp was removed, the doctor will tell you whether to avoid any medicines for a few days. Wondering what it actually feels like? Read is colonoscopy painful?
Questions patients ask us
Can I have tea before a colonoscopy?
Yes, plain tea or black coffee without milk is fine during the clear-liquid phase, until the time the clinic asks you to stop all fluids.
What if I vomit the prep?
Wait 30 to 60 minutes and restart slowly. If you can't finish it, phone the clinic; it may be safer to move the test.
Can I take my blood pressure tablet?
Usually yes, early in the morning with a sip of water. Confirm it when you book.
I have diabetes. Is the prep safe for me?
Yes, with a plan. Your doses are adjusted for the liquid day, and you should check your sugar more often. Keep glucose water handy in case it drops.
Have a question about your own preparation? Book an appointment or consult online with Dr. Shrihari Anikhindi, and we will go through it with you.
Medically reviewed by Dr. Shrihari Anikhindi, MBBS, MD, DNB (Gastroenterology), MRCP (SCE), gastroenterologist and advanced endoscopist at Medigest Gastro, Liver & Endoscopy Clinic, Delhi. This article is general information. Please talk to your own doctor about your health.