What to look out for after a gastroscopy or colonoscopy? Eating, driving after sedation, test results and when to seek medical attention
After a gastroscopy patients should stay fasted for about 1 hour, and after a colonoscopy can eat once the effect of the anaesthetic or sedative has worn off; patients who have had a sedative injection should not operate heavy machinery, sign legal documents or drive for the rest of the day (Cancer Online Resource Hub, ‘Stomach Cancer’ and ‘Colorectal Cancer’ pages, April 2026). For individual patients, the treating doctor's instructions prevail.
What to look out for after a gastroscopy or colonoscopy?
The table below sets out what patients are told to note after upper endoscopy (gastroscopy) and after colonoscopy respectively (Cancer Online Resource Hub, ‘Stomach Cancer’ and ‘Colorectal Cancer’ pages, April 2026); for individual patients, the instructions of the treating doctor and healthcare staff prevail.
| Item | Gastroscopy (‘Stomach Cancer’ page) | Colonoscopy (‘Colorectal Cancer’ page) |
|---|---|---|
| Eating after the test | Stay fasted for about 1 hour, to let the effect of the throat anaesthetic or sedative wear off and prevent choking | Can eat once the effect of the anaesthetic or sedative has worn off |
| Patients who have had a sedative injection | Must not operate heavy machinery, sign legal documents or drive for the rest of the day, to prevent accidents | Must not operate heavy machinery, sign legal documents or drive for the rest of the day, to prevent accidents |
| Medicines | Complete the course of medication as instructed by healthcare staff | Complete the course of medication as instructed by healthcare staff |
| Test results and follow-up | If you have questions about the test results or medication, ask healthcare staff | Ask about the test results and the date of the next follow-up |
| What is commonly felt during and after the test | During the test, nausea, a mild sore throat and bloating or discomfort in the upper abdomen are common; the throat anaesthetic can also cause difficulty swallowing for more than an hour; these usually disappear within 24 hours | During the test, abdominal bloating and mild discomfort are common |
| Serious complications | The chance of intestinal perforation, bleeding, death, cardiopulmonary complications and infection is very low, but varies with the patient's condition and the examination and treatment methods; patients should ask the treating doctor | Intestinal perforation, bleeding, cardiopulmonary complications, infection and acute intestinal obstruction are generally less than 1% likely, varying with the patient's condition and the treatment method; for patients who have endoscopic treatment such as polyp removal, the chance of serious complications rises sharply |
What situations after the test mean I should seek medical attention?
What each source says about seeking medical attention is in the table below. For individual patients, the instructions of the treating doctor and healthcare staff prevail; for preparation before gastroscopy and colonoscopy, see Gastroscopy and colonoscopy: public or private?.
| Source | What it says about seeking medical attention |
|---|---|
| Cancer Online Resource Hub, ‘Stomach Cancer’ page (revised 28 April 2026) | After the test, for mild discomfort, or questions about the test results or medication, ask healthcare staff; if a serious event occurs, such as gastrointestinal bleeding or severe abdominal pain, the patient ‘should seek medical advice at the nearest Accident and Emergency Department’; in an urgent situation call 999 for an ambulance (this site’s note) |
| Cancer Online Resource Hub, ‘Colorectal Cancer’ page (revised 28 April 2026), ‘Follow up’ section | After the test, for mild discomfort, or questions about the test results or medication, ask healthcare staff; if a serious event occurs, such as bleeding in the stool or severe abdominal pain, the patient ‘should seek medical advice at the nearest Accident and Emergency Department’; in an urgent situation call 999 for an ambulance (this site’s note) |
| Cancer Online Resource Hub, ‘Colorectal Cancer’ page (revised 28 April 2026), ‘Risk and complications’ section under ‘How to investigate and make diagnosis for Colorectal Cancer?’ | After the test, if abdominal pain, blood in the stool or similar occurs, the patient ‘should seek immediate advice from doctors’ |
| Department of Health Colorectal Cancer Screening Programme, Participant Guidebook (December 2025 edition, for programme participants) | In the next few days and weeks after the test, keep watching your condition; if unusual features appear, ‘prompt medical attention should be sought’; and please read carefully the important reminders given by the Colonoscopy Specialist after the test |
How long should I stay after a colonoscopy? When will I get the results?
After a colonoscopy, programme participants are observed and must be confirmed by the Colonoscopy Specialist to be in stable health before being allowed to leave, and are recommended to be accompanied home by a family member (Department of Health Colorectal Cancer Screening Programme, Participant Guidebook, December 2025 edition).
For programme participants whose colonoscopy result is normal, the Colonoscopy Specialist may already have explained the result on the day of the examination, and the participant may not need a separate follow-up visit; for any result that is not normal, the Colonoscopy Specialist will arrange a clinic consultation after the examination to explain the details and, depending on the situation, suggest a follow-up appointment, arrange other post-procedural care or make a referral (Department of Health Colorectal Cancer Screening Programme, ‘After colonoscopy’ page, revised August 2018). The doctor decides on one or more follow-up visits depending on the result and clinical need (Colorectal Cancer Screening Programme, Participant Guidebook, December 2025 edition).
For what happens after a positive faecal occult blood test, see What happens after a positive faecal occult blood test.
What is different after polyps are removed during a colonoscopy?
When a polyp is found, the doctor places a metal loop through the colonoscope and uses electric current to remove the polyp, generally for polyps smaller than 2 cm, and the patient feels no pain during the removal; most polyps are benign, and only a small proportion turn into cancer (Cancer Online Resource Hub, ‘Colorectal Cancer’ page, April 2026). For patients who have endoscopic treatment such as polyp removal, the chance of serious complications rises sharply, and patients should ask the treating doctor for details (Cancer Online Resource Hub, ‘Colorectal Cancer’ page, April 2026).
If polyps are removed during the colonoscopy, the Programme's Standard Package of Colonoscopy Service includes the pathological examination and report on the removed polyps (Department of Health Colorectal Cancer Screening Programme, Participant Guidebook, December 2025 edition).
Preparation before the test, public or private, how to check fees?
For public and private gastroscopy and colonoscopy compared, see Gastroscopy and colonoscopy: public or private?; for private fees, see Gastroscopy fees compared and Colonoscopy fees compared; for the English names, see Gastroscopy and Colonoscopy; and for choosing a doctor, see How to choose a gastroenterologist.
Frequently asked questions
When can I eat and drink after a gastroscopy?
After a gastroscopy the patient should stay fasted for about 1 hour, to let the effect of the throat anaesthetic or sedative wear off and prevent choking; patients should complete the course of medication as instructed by healthcare staff (Cancer Online Resource Hub, ‘Stomach Cancer’ page, April 2026). For individual patients, the treating doctor's instructions prevail.
When can I eat after a colonoscopy?
After a colonoscopy the patient can eat once the effect of the anaesthetic or sedative has worn off; patients should ask about the test results and the date of the next follow-up (Cancer Online Resource Hub, ‘Colorectal Cancer’ page, April 2026). For individual patients, the treating doctor's instructions prevail.
Can I drive after having a sedative?
If the patient has had a sedative injection, the patient should not operate heavy machinery, sign legal documents or drive for the rest of the day, to prevent accidents (Cancer Online Resource Hub, ‘Stomach Cancer’ and ‘Colorectal Cancer’ pages, April 2026).
What situations after a colonoscopy mean I should seek medical attention?
If a serious event occurs, such as bleeding in the stool or severe abdominal pain, the patient ‘should seek medical advice at the nearest Accident and Emergency Department’ (Cancer Online Resource Hub, ‘Colorectal Cancer’ page, ‘Follow up’ section, April 2026); if abdominal pain, blood in the stool or similar occurs after the test, the patient ‘should seek immediate advice from doctors’ (same page, ‘Risk and complications’ section under ‘How to investigate and make diagnosis for Colorectal Cancer?’, April 2026). For mild discomfort or questions, ask healthcare staff (Cancer Online Resource Hub, ‘Colorectal Cancer’ page, April 2026).