Why prep matters so much

A colonoscopy lets the specialist examine the lining of your colon for polyps and abnormalities. If there is faecal material in the way — even small amounts — areas can be hidden and small polyps missed.

Good prep increases the polyp detection rate and reduces the chance you’ll need to repeat the procedure. Repeat colonoscopies because of poor prep cost time, money and a second round of preparation. It is genuinely worth doing the prep well the first time.

The diet — 1–2 days before

From two days before, switch to a low-residue diet — white bread, white rice, plain pasta, chicken, fish, eggs, well-cooked vegetables without skins. Avoid red meat, high-fibre foods, seeds, nuts, popcorn, leafy greens, raw vegetables and skins of fruit.

From the day before, switch to clear fluids only. “Clear” means you can see through it — water, black tea, black coffee, clear apple juice, clear broth, lemonade, jelly (not red or purple), ice blocks.

Avoid anything red or purple for the 24 hours before — coloured fluids can be mistaken for blood during the procedure.

The prep drink — when and how

Most modern prep drinks are split-dose: half taken the evening before, half taken 4–6 hours before the procedure on the morning of. This works better than the old single-dose evening prep.

The drink itself comes as a powder that you mix with water (usually 1–2 litres) and consume over a few hours. Sip it slowly — guzzling triggers nausea. Chilled is usually easier than room temperature. Drinking through a straw helps some patients.

Stay close to a bathroom from about an hour after the first dose. The output progresses from solid to liquid to clear/yellow over the next few hours.

Tips for getting through it

• Chill the prep drink in the fridge — much easier to tolerate cold.
• Sip steadily, don’t gulp — drink the prescribed volume over 1–2 hours, not 10 minutes.
• Use a straw — bypasses your tongue’s taste receptors.
• Have a chaser ready — a sip of clear lemonade or clear apple juice between mouthfuls helps.
• Suck on a lemon wedge between sips if the taste is overwhelming.
• Stay hydrated with extra clear fluids — dehydration makes the headache and fatigue worse.
• Block out the time — don’t try to work, drive or have visitors during the active prep window.

What if you can’t tolerate it?

If you vomit the prep up, wait 30 minutes and try again at half the rate. If you still can’t keep it down, call us — we have alternative prep regimens (capsule-based options, lower-volume formulations) that some patients tolerate better.

Don’t give up and don’t go ahead with a partial prep without telling us — an incomplete prep risks an incomplete procedure.

Day-of-procedure rules

Take the second half of the prep at the time we specified (typically 4–6 hours before your booked time). Stop all clear fluids 2 hours before the procedure — nothing in your stomach.

Take essential medications with a small sip of water unless told otherwise. Diabetes medications and blood thinners follow specific instructions we’ll have given you.

Wear loose, comfortable clothing. Bring your support person, your referral letter and your Medicare card.

About your specialist — Dr Goutham Sivasuthan

Dr Goutham Sivasuthan is an Australian-trained Fellow of the Royal Australasian College of Surgeons (FRACS), with conjoint accreditation by the Gastroenterological Society of Australia (GESA) in both upper GI endoscopy and colonoscopy. He completed his medical degree at the University of Queensland and his advanced training across Brisbane’s tertiary hospitals.

Dr Goutham consults and operates exclusively at Brisbane-region day-surgery and hospital facilities, and is the only clinician you’ll meet through your care — from your first consultation, through your procedure, to your follow-up. He is committed to no-gap care for insured patients and transparent pricing for everyone else.

Frequently asked questions

Can I drink coffee during prep?

Yes — black coffee (no milk) is permitted as a clear fluid up to 2 hours before the procedure. Avoid coffee with milk and avoid red or purple flavoured drinks.

What if I’m diabetic?

We provide specific instructions. Most diabetic medications are adjusted on prep day; insulin doses are usually reduced. Bring your glucose meter and check more often than usual. Severe hypoglycaemia is rare but worth being prepared for.

Can I take my regular blood pressure medication?

Yes, with a sip of water on the morning of the procedure unless we’ve specifically said otherwise.

What if I’m constipated and the prep doesn’t seem to be working?

Some patients need a bit more time. If you haven’t started passing clear/yellow fluid 6 hours after the prep, call us — we can advise. Don’t add more prep drink without instruction.

Will I be exhausted afterwards?

Most patients feel tired the morning of the procedure from being up for the prep. After the procedure, the sedation wears off over a few hours and most people are back to normal energy by the next morning.

This article is part of our specialist series on bowel and gut health. For the full overview, see our main service page.