Diet Before and After Colonoscopy

Good planning makes the prep easier. Follow the written instructions of your unit; the points below are general.

• Read your unit’s instructions as soon as you get them, mark the key times in your diary or phone, and phone the unit if anything is unclear.
• Stay near a toilet once you start the solution, and use barrier cream to protect the skin.
• Take the second dose at the time instructed, even if you have already passed clear liquid; do not skip it. Drink the solution chilled, through a straw, with a slice of lemon (not red), and take short breaks if you feel sick.
• Arrange a responsible adult to accompany you and take you home; do not drive, sign contracts or make important decisions for 24 hours after sedation.
• If you want to avoid Ramadan clashes, ask your unit; non-urgent colonoscopy is often scheduled outside Ramadan because fasting and prep fluids do not fit together. See the article on Ramadan with a GI or liver condition.

The general pattern: low-fibre food for 1 to 3 days (your unit decides how long), then only clear liquids on the last day until about 2 hours before the procedure, then nothing by mouth. Our planner uses: seeds and nuts stopped 3 days before, low-residue diet from 3 days before, clear liquids the day before.

• Low-residue days (usually the 1 to 3 days before): white bread, white rice, pasta, plain potato without skin, eggs, chicken, fish, tender lean meat, plain yoghurt or cheese if your unit allows, clear soups, well-cooked skinless vegetables only if your unit allows, and plain biscuits.
• Avoid on those days: seeds and nuts, popcorn, whole grains, brown bread, bran, raw vegetables and salad, fruit with skins or seeds, dried fruit, dates, beans, lentils, chickpeas, foul and hummus, harees and other wheat dishes, and kabsa or mandi with raisins, nuts or whole spices. They can leave residue that hides the lining.
• Clear-liquid day (the day before): water, clear broth, apple or white grape juice without pulp, tea or coffee without milk, clear soft drinks, sports drinks, plain jelly, ice pops and clear boiled sweets. Choose light-coloured fluids and avoid milk, laban, orange juice with pulp, thick soups, alcohol, and anything red, purple or blue (for example some juices, jelly, and Vimto-type drinks), which can look like blood in the bowel.
• Drink plenty of clear fluids all day to avoid dehydration, in addition to the prep solution, unless your doctor limits your fluids for heart, kidney or liver disease. Do not chew solid food; plain sugar-free chewing gum or clear sweets may be allowed by some units.
• Timing: take the prep in two parts (evening before and morning of the procedure). The second dose is usually started 4 to 5 hours before the procedure (following your unit’s exact time) and finished at least 2 hours before it. Clear liquids may stop about 2 hours before sedation, then nothing by mouth. Afternoon procedures may use morning dosing, as your unit instructs.
• Diabetes: ask your team in advance how to adjust insulin and tablets on the clear-liquid day, because the risk of low sugar is real. Keep sugary clear drinks nearby and check glucose often. Some diabetes tablets (SGLT2 inhibitors) and weekly GLP-1 injections often need special instructions; do not change them on your own.
• Kidney, heart or liver disease, pregnancy, or being frail: ask for individual advice. Some people need a different prep, extra monitoring or to do the prep in hospital.
• After the colonoscopy: once you are awake and the nurse agrees, start with water and a light snack (toast, rice, soup, tea) and move on to your normal meals later the same day or the next, unless told otherwise. Expect gas, so walking and passing wind help. Drink fluids to replace what you lost. No alcohol for 24 hours.
• Restarting fibre: bring back vegetables, fruit, wholegrains and legumes over the following days rather than all at once, with plenty of fluids, to avoid bloating and constipation. Long-term, a diet rich in fibre, vegetables, fruit and wholegrains, with less red and processed meat and no alcohol or smoking, is linked with lower bowel cancer risk.
• Day of polyp removal or biopsy: if polyps were removed, follow your unit’s advice about avoiding heavy lifting and strenuous exercise, long-haul travel and alcohol for a period (often about 1 to 2 weeks after large polyp removal), and about restarting aspirin or blood thinners. Do not restart or avoid them on your own. Eat normal soft foods; there is usually no need for a special diet unless told.

Medicines need a plan before the day. Ask your unit; no doses are given here.

• Iron tablets are usually stopped about a week before (the planner suggests 7 days) because they darken stool and coat the lining; check with your unit.
• Blood thinners (warfarin, apixaban, rivaroxaban, clopidogrel and others) and aspirin: never stop on your own. Your unit and prescribing doctor decide who needs to hold and who needs a bridge.
• Take your regular heart, blood-pressure, thyroid and other essential medicines as instructed, usually with a sip of water; ask about diabetes tablets, insulin and GLP-1 injections.
• Avoid anti-diarrhoea tablets and fibre supplements during the prep days unless instructed, and avoid laxatives other than the prescribed prep.
• Tell the unit about allergies, kidney disease, heart failure, pregnancy and any previous reaction to a prep.

What happens in the unit, and how the diet fits with it.

• Most colonoscopies are done with sedation or sometimes with anaesthesia; the fasting rule of about 2 hours for clear liquids exists to make this safe.
• The doctor may remove polyps and take biopsies during the same procedure.
• If the prep was poor, the doctor may wash the bowel, ask you to repeat the procedure after a stronger preparation, or choose another test.
• Follow-up of polyp results and the date of the next check are decided by your doctor from the findings and pathology.