Colonoscopy Preparation & Diet Guide
Everything you need for the days before your scope: what to eat, and how to take your Fortrans bowel prep. A clean colon means a clearer view for your doctor, and a safer, more accurate scope.
Dr. John Hsiang is a distinguished gastroenterologist in Singapore with extensive training and experience in digestive health. He obtained his Fellowship of the Royal Australasian College of Physicians in Gastroenterology in 2012 and holds a PhD in viral hepatitis and fatty liver disease research.
He provides care for a broad range of digestive and liver concerns, combining thorough evaluation with tailored management to support patients’ long-term well-being.
Dr Hsiang is skilled in performing gastroscopy (upper endoscopy) and colonoscopy to investigate symptoms, detect stomach and colon cancers at an early stage, and provide timely treatment options.
With a commitment to individualised care, he applies an evidence-based approach that prioritises accuracy, effectiveness and patient comfort at every stage of diagnosis and treatment.
Languages Spoken:
English, Mandarin and Hokkien
Fellowship Trained Specialist
20+ Years of Clinical Experience
Your bowel prep: choose your scope time
You will take all 4 litres of Fortrans the night before. Because a morning scope follows soon after, one full evening dose gives a clean colon.
If your doctor has told you to, take 2 Dulcolax tablets about 1 hour before you start the Fortrans. This is only for patients who tend to be constipated.
Mix 4 sachets of Fortrans into 4 litres of water and drink it steadily over about 4 hours, finishing each litre within roughly an hour. To make it easier to drink: chill it first, and if you like, dissolve the sachets in a mix of half plain water and half coconut water, sugarcane juice or honey water instead of plain water alone. If you have diabetes, please check with us before using sugarcane juice or honey water.
• You may take essential medicines (blood pressure, thyroid) with a small sip of water.
• No solid food for six hours and no liquid for four hours BEFORE the scheduled procedure time
When to stop drinking (examples):
| Your scope time | Stop all fluids by |
|---|---|
| 8:00 am | 4:00 am |
| 9:00 am | 5:00 am |
| 10:00 am | 6:00 am |
| 11:00 am | 7:00 am |
| 12:00 noon | 8:00 am |
Admission is usually 2 hours before your procedure time. Our clinic will confirm your exact admission and scope timing.
You will split your Fortrans into 3 litres the night before and the last 1 litre on the morning of your scope. Splitting the dose this way gives the cleanest possible view for an afternoon procedure.
If your doctor has told you to, take 2 Dulcolax tablets about 1 hour before your first Fortrans dose.
Mix 3 sachets into 3 litres of water and drink steadily over about 3 hours, finishing each litre within roughly an hour. To improve the taste: chill it, and if you like, dissolve the sachets in half plain water and half coconut water, sugarcane juice or honey water. Diabetic patients, please check with us first.
Mix the last sachet into 1 litre of water, again using half plain water and half coconut water, sugarcane juice or honey water if you wish, and drink it over about 1 hour. Time it so you finish this 1 litre at least 4 hours before your scope.
• No solid food for at least 6 hours before your scope (you are on prep and clear fluids only).
• After the 1 litre, you may sip clear fluids up until 4 hours before your scope, then stop everything.
• Essential medicines (blood pressure, thyroid) may be taken with a small sip of water.
When to drink the morning 1 litre and stop (examples):
| Your scope time | Finish the 1 L by | Stop all fluids by |
|---|---|---|
| 12:00 noon | 8:00 am | 8:00 am |
| 1:00 pm | 9:00 am | 9:00 am |
| 2:00 pm | 10:00 am | 10:00 am |
| 3:00 pm | 11:00 am | 11:00 am |
| 4:00 pm | 12:00 noon | 12:00 noon |
Admission is usually 2 hours before your procedure time. Our clinic will confirm your exact admission and scope timing.
What you can and cannot eat (2 days before)
A low residue diet means low fibre foods that leave little behind in the colon. It's easier to follow than a water-only diet, and cleans just as well. Simple rule: soft, plain, pale, no skins, no seeds, no vegetables.
✓ You CAN have
- Plain white rice, plain white bread
- Porridge or congee (pork, fish or chicken, no vegetables or garnish)
- Bee hoon, kway teow or mee tai mak soup (clear broth and plain noodles only). Remove all vegetables, spring onion and fried shallots.
- Steamed or boiled fish and chicken
- Egg (steamed, boiled or plain omelette)
- Steamed tofu, plain steamed prawns (no sauce)
- Plain chicken rice (no dark sauce, chilli or vegetable)
- Plain yoghurt, butter, kaya
- Clear soups, plain jelly (yellow/orange), steamed cake, plain bao (no filling)
- Clear drinks: water, isotonic drink such as 100 Plus (non-carbonated / no gas), apple juice (no pulp), barley water, chrysanthemum tea and kopi-o / teh-o (coffee & tea without milk)
✗ Please AVOID
- All fruit and vegetables (including salad and garnish)
- Brown rice, red rice, quinoa, glutinous / sticky rice
- Wholemeal / multigrain bread & biscuits, chapati, oats, cereal
- Milk, Milo, soya milk, chocolate drinks, cheese, bubble tea
- All fried food (incl. kerupuk & fried shallots), nuts & seeds
- Red meat, beans, lentils
- Spicy / rich dishes: laksa, bak kut teh, tom yum, fried Hokkien mee, claypot chicken rice, mapo tofu, Korean & Thai spreads
- Stuffed bao, garlic bread, jam, biscuits & cakes
- All fruit (durian, avocado, kiwi, grapes, dragonfruit, banana)
- Dark soy sauce, black pepper, heavy spices, chilli/black-pepper crab & saucy seafood
- Red or purple drinks such as tomato or grape juice, because the colour can look like blood inside the colon
A picture guide to low-residue foods
Soft, plain and pale is the rule. Here are good choices at a glance.
Your medications before the scope
Keep taking (with a small sip of water)
Blood pressure medicine and thyroid medicine can be continued as usual, even on the morning of the scope.
Stop before the scope
• Blood thinners (for example aspirin/Cardiprin, warfarin, clopidogrel/Plavix, ticagrelor, rivaroxaban or apixaban). Only stop these if your doctor has told you to, and follow the exact dates given.
• TCM & herbal supplements (ginseng, ginkgo, garlic, ephedra, St John's Wort, jamu, ayurvedic, etc.) and iron tablets should be stopped 1 week before the procedure, as these can raise bleeding risk if a polyp needs to be removed.
• Diabetes medicine: please follow the separate diabetes medication sheet.
Getting through the prep comfortably
Fortrans is safe. It is not absorbed by the body and works simply by flushing the bowel with water. For most people the volume is the hard part, not the medicine itself. The taste and temperature tips are built into the drinking steps above, and a few more things help.
- Drink each litre steadily, aiming to finish it within about an hour.
- If you feel nauseous, pause for 20 to 30 minutes, walk around and gently massage your tummy, then continue more slowly.
- Keep drinking until you have finished all 4 litres and the liquid you pass runs clear.
Chilling and flavouring make the prep easier to finish, which is what matters. They do not change how well the medicine cleans the bowel.
How do I know when I'm ready?
Keep drinking until what you pass into the toilet is a clear, light yellow or light orange liquid with no solid bits. Deep brown or amber, or anything with particles, means you should keep going. Use the chart below to check your progress.
When to call us
• Keep vomiting and cannot keep the prep down
• Have severe stomach pain or bloating that will not settle
• Pass no stool at all after several hours of drinking the prep
• Feel very dizzy, weak or passing very little urine (signs of dehydration)
On the day: a few reminders
• Bring your NRIC. Leave jewellery and valuables at home and remove nail polish.
• You will be sedated, so arrange a responsible adult to take you home.
• After the scope, do not drive, operate machinery, sign legal documents, exercise or drink alcohol for the rest of the day.
• Please be punctual. Admission is usually 2 hours before your scope.
Read our guide to the cost of colonoscopy in Singapore, including MediSave coverage and what affects the price.
Patient Information
How many days before a colonoscopy should I change my diet?
Can I drink kopi or teh before my colonoscopy?
Can I drink milk or eat cheese?
What Singapore hawker foods can I eat?
Good choices include plain porridge or congee, bee hoon or kway teow soup (clear broth and plain noodles only, no vegetables or garnish), steamed fish, boiled chicken, steamed egg, steamed tofu, plain steamed prawns and plain chicken rice without dark sauce or vegetables.
How do I make the Fortrans easier to drink?
What if I vomit or can't keep the prep down?
How long does Fortrans take to work?
Should I stop my TCM herbs or supplements?
Consult Our Specialist
Experiencing digestive symptoms or discomfort? Speak to our gastroenterologist for a clearer understanding of your condition and treatment options.
You may book an appointment using our contact form or call the clinic at 8228 8469
