Capsule endoscopy means swallowing a camera about the size of a large vitamin pill. It takes tens of thousands of pictures as it travels through your small bowel, the part that’s hard to reach with other camera tests. This guide explains why it’s done, how to prepare, what the day is like, what it can find, and the small risk of the capsule getting stuck.
Key points
- The capsule is about 26mm by 11mm and is swallowed with water. It passes out naturally in your poo.
- It’s mainly used to look for hidden bleeding or inflammation in the small bowel, often after a gastroscopy and colonoscopy were normal.
- You’ll stop iron tablets about a week before, and usually take a bowel preparation the day before.
- You wear a recorder for about 8 hours and can go about quiet activities.
- The main risk is the capsule getting stuck. This is uncommon, and more likely if you have a known narrowing of the bowel.
What is capsule endoscopy?
Your small bowel is around 6 metres long, and most of it is out of reach of a gastroscopy from above or a colonoscopy from below. A capsule camera solves this. As it’s carried along by the natural movement of your gut, it takes pictures and sends them to a recorder you wear. Afterwards, a trained specialist reviews the images as a video.[1,3]
Why you might have a capsule endoscopy
- iron deficiency anaemia or bleeding where a gastroscopy and colonoscopy haven’t found the cause[3,4]
- suspected or known Crohn’s disease in the small bowel[3]
- to check on coeliac disease that isn’t responding as expected[3]
- to look for polyps or other changes in the small bowel, for example in some inherited conditions[3]
What it can find
Common findings include:[3]
- Small abnormal blood vessels (angiodysplasia). These are one of the commonest causes of hidden bleeding from the small bowel. They can often be treated with a heat probe during a further endoscopy.
- Inflammation or ulcers, for example from Crohn’s disease or from anti-inflammatory painkillers such as ibuprofen.
- Polyps or, rarely, tumours.
Often the capsule is normal, which is useful information too. It helps your team decide whether more tests are needed or whether treatment, such as iron, can simply continue.
Before the test
- About a week before: stop iron tablets. You may also be asked to stop some painkillers, such as codeine, which slow the gut.[1]
- The day before: you’ll usually have a light diet, then clear fluids, and take a bowel preparation in the evening to give the camera a clear view.[1]
- From midnight: nothing to eat or drink until the test, unless your instructions say otherwise.
If you’ve had bowel surgery or Crohn’s disease, or have symptoms of a blockage, such as severe cramping and vomiting after meals, tell the team. You may be asked to swallow a dissolvable “patency” capsule first, to check a capsule can pass safely.[2,3]
Tell the team if you have a pacemaker or other implanted device, or difficulty swallowing tablets.[1]
On the day
- Sensors or a belt are put on your tummy, connected to a small recorder you wear at your waist or over your shoulder.
- You swallow the capsule with a glass of water. It’s smooth and most people find it easy.
- You can usually leave the unit and go about quiet activities. Avoid heavy exercise and bending, and stay away from strong magnetic fields.
- You’ll be told when you can drink (often after 2 hours) and eat a light meal (often after 4 hours).[1]
- After about 8 hours, the equipment is removed or returned to the unit.[1]
What happens to your pictures
Reading capsule studies is part of my job, and I trained for it on a specialist capsule endoscopy course. Each study produces tens of thousands of images, and every one has to be looked at carefully, so please don’t expect results on the day.
The most common reasons we do this test are to look for Crohn’s disease in the small bowel, and to investigate iron deficiency anaemia that keeps coming back.
With iron deficiency anaemia, it’s not uncommon for the capsule to be normal. That’s still useful, because it helps rule things out. When it does find something, such as a small patch of abnormal blood vessels in a section of bowel no other camera can reach, it can explain months or years of anaemia, and it can often be treated.
The most helpful thing you can do is follow the preparation and eating times on your instructions. A clean bowel gives the clearest pictures.
Ben JohnsonAdvanced Clinical Practitioner, Gastroenterology
Passing the capsule
The capsule usually passes in your poo within a day or two. You won’t normally feel it, and you don’t need to retrieve it. It’s designed to be flushed away.[1]
Important: no MRI until the capsule has passed
Don’t have an MRI scan until you’re sure the capsule has passed, because the magnet could damage your bowel. If you haven’t seen it pass after 2 weeks and need an MRI, contact the unit, who may arrange an X-ray.[1]
Risks
- The capsule getting stuck (retention). This is uncommon. In studies it happens in about 2 in 100 people having the test for bleeding, and more often in people with known Crohn’s disease.[2] A patency capsule beforehand reduces the risk. A stuck capsule often passes with medicine, or occasionally needs removing with an endoscope.[2,3]
- Not seeing the whole small bowel, if the capsule moves slowly or the view is poor.[3]
- Rarely, difficulty swallowing the capsule. If this happens, it can be placed with an endoscope.
Contact the unit or NHS 111 if, after the test, you have:
- tummy pain, bloating or vomiting that won’t settle
- being unable to pass wind or open your bowels
These can be signs the capsule is stuck. If the pain is severe, go to A&E and tell them you’ve had a capsule endoscopy.
Results
The images are reviewed by a trained specialist after the test. Results are usually sent to the doctor who referred you within a few weeks.[1] If something is found that needs treatment or a sample, you may be offered a further test called an enteroscopy, which uses a longer camera.[3]
Frequently asked questions
Is it painful?
No. Most people feel nothing once the capsule is swallowed.
Can I go to work?
Light office work is often fine, but avoid strenuous activity and stay away from strong magnetic fields. Ask the unit what suits your job.
Can it take biopsies?
No. If something is seen, you may need another test, such as an enteroscopy, to take samples or give treatment.
What if I don’t see the capsule pass?
Many people don’t notice it. That’s only a concern if you need an MRI, or develop pain, bloating or vomiting.
References
- Royal Berkshire NHS Foundation Trust. Wireless capsule endoscopy (patient information, October 2025). https://www.royalberkshire.nhs.uk/media/shspjjlq/wireless-capsule-endoscopy_oct25.pdf
- O’Hara F, Walker C, McNamara D. Patency testing improves capsule retention rates but at what cost? Frontiers in Medicine 2023. https://www.frontiersin.org/journals/medicine/articles/10.3389/fmed.2023.1046155
- Pennazio M, Rondonotti E, Despott EJ, et al. Small-bowel capsule endoscopy and device-assisted enteroscopy for diagnosis and treatment of small-bowel disorders: European Society of Gastrointestinal Endoscopy (ESGE) Guideline, update 2022. Endoscopy 2023;55:58–95. https://www.thieme-connect.com/products/ejournals/html/10.1055/a-1973-3796
- Snook J, et al. British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults. Gut 2021;70:2030–2051. https://gut.bmj.com/content/70/11/2030