Hannah Lynes

NHS colonoscopy instructions: when to take the laxatives

in Health

When do NHS hospitals tell people to take the laxatives before a colonoscopy? This is part of my series comparing NHS colonoscopy preparation instructions.

The laxative timetable affects when you have to stop eating solid foods, what time you can get to bed the night before and what time you have to get up on the morning of the procedure.

European guidance, endorsed by the British Society of Gastroenterology, recommends taking the final dose within five hours of the colonoscopy, so timetables are expected to differ between morning and afternoon appointments. The lists below keep appointment times separate and compare each medicine only with the same medicine.

Of the timetables listed below, 94 (from 39 NHS organisations) guarantee a gap of more than five hours between the final dose and the colonoscopy.

Morning appointments

Plenvu

All doses the previous day

Doses on both days

Moviprep

All doses the previous day

Doses on both days

Picolax (two sachets)

All doses the previous day

Doses on both days

Klean-Prep (up to four litres)

All doses the previous day

Afternoon appointments

Plenvu

Doses on both days

All doses on procedure day

Moviprep

Doses on both days

All doses on procedure day

Picolax (two sachets)

All doses the previous day

Doses on both days

Klean-Prep (up to four litres)

Doses on both days

Evening appointments

Klean-Prep (up to four litres)

All doses on procedure day

Second dose timed from the appointment

Three hospitals time the second dose from the actual appointment rather than giving a fixed clock time. In each case it is five hours before the appointment, the outer limit of the European guidance.

  • Guy’s and St Thomas’: first dose of Moviprep or Plenvu at 4pm the day before (Picolax or CitraFleet at 5pm, after Senna at 4pm); second dose five hours before the colonoscopy.
  • Nottingham University Hospitals: for appointments before 6pm, first dose at 7pm the day before and second dose five hours before the appointment (for example 4am for a 9am appointment, 6am for 11am, 10am for 3pm). For evening appointments, first dose at 8am on the day, then five hours before.
  • Sherwood Forest Hospitals: Plenvu, May 2024. First dose at 7pm the day before and second dose five hours before the appointment (for example 4am for a 9am appointment). The evening-appointment leaflet gives 8am on the day, then five hours before.

Other standard instructions

Some hospitals’ standard instructions do not fit the lists above, so I have not set them out in detail. They use three sachets of Picolax or CitraFleet (Ashford and St Peter’s, Salisbury, Southampton); add Senna or bisacodyl tablets, or combine two medicines (Barking, Havering and Redbridge, Blackpool, East and North Hertfordshire, Frimley, Kingston and Richmond, Norfolk and Norwich, North Tees and Hartlepool, Royal Devon, The Royal Marsden, Shrewsbury and Telford, Surrey and Sussex, University Hospitals Coventry and Warwickshire, Morecambe Bay, Worcestershire); or do not say which appointment times they cover, or are unclear (Barts Health, Dudley, Northern Care Alliance (Salford), Royal Free, Royal Surrey, Salisbury (Klean-Prep), UCLH (sodium picosulfate with magnesium citrate), University Hospitals Birmingham (Plenvu)).

About this comparison

The lists use NHS instructions that were publicly available online, checked up to 12 November 2026. They cover routine colonoscopy; instructions that also cover flexible sigmoidoscopy are included where the colonoscopy schedule is clear. Instructions for gastroscopy and colonoscopy at the same appointment, bowel cancer screening, extended or enhanced preparations, and manufacturer timetables published on NHS websites are left out.

Times are for the day before the colonoscopy unless they are marked as the procedure day. An organisation can appear in more than one list where one leaflet covers several appointment times or it publishes different leaflets. “Morning” and “afternoon” do not cover exactly the same hours in every hospital. For the five-hour figure, I counted a timetable only where the last dose starts more than five hours before the earliest possible appointment in that session, taking 12 noon as the earliest afternoon appointment. A few leaflets give the time to prepare a dose rather than to drink it. Older leaflets are included and labelled; editions known to have been replaced are left out.

The lists contain 178 entries from 57 NHS organisations. This is not a survey of every hospital: some send medicine timetables to patients rather than publishing them online, so if a hospital is not listed, I did not find its timetable online. This is a comparison of published instructions, not advice to change the preparation prescribed by your own hospital.

Sources checked up to 12 November 2026. See also when low-fibre diets start, when to stop eating solid food and which foods are allowed.

Last updated: November 13, 2026

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