Symptoms and conditions
What is inflammation in the gut? Early signs you should not ignore
Inflammation in the gut is the immune system’s response to injury or infection in the lining of the digestive tract. Its early signs are diarrhoea lasting more than two to four weeks, blood or mucus in the stool, urgency, stools that wake you at night, and unexplained weight loss or tiredness. A stool test and blood tests detect it, and colonoscopy shows the cause.
In short
- Short-lived inflammation after an infection is common and settles.
- Inflammation that persists has a cause that can usually be identified: infection, inflammatory bowel disease, coeliac disease or a medicine.
- Night-time symptoms, bleeding and weight loss separate inflammation from irritable bowel syndrome.
- A stool marker called faecal calprotectin is a simple first test.
What are the early signs?
- Loose stools for more than two to four weeks
- Blood or mucus in the stool
- A sudden, urgent need to pass stool
- Waking from sleep to pass stool
- Cramping abdominal pain
- Weight loss, poor appetite or fever
- Tiredness with a low blood count
- Mouth ulcers, painful joints or sore, red eyes
What causes inflammation in the gut?
Infections
Bacteria, amoebae and other parasites. Common, and usually treatable within days.
Inflammatory bowel disease
Ulcerative colitis and Crohn’s disease: long-term, immune-driven inflammation. See inflammatory bowel disease.
Coeliac disease
An immune reaction to gluten that inflames the small intestine. See gluten sensitivity.
Medicines
Anti-inflammatory painkillers are a frequent cause of inflammation and ulcers anywhere in the gut.
H. pylori
The cause of most long-standing inflammation of the stomach. See gastritis.
Other causes
Tuberculosis of the intestine, diverticulitis, reduced blood supply to the bowel, and a form of colitis visible only under the microscope.
How is it different from IBS?
| Inflammation | Irritable bowel syndrome | |
|---|---|---|
| Blood in stool | Common | Absent |
| Night-time symptoms | Common | Rare |
| Weight loss, fever | Can occur | Absent |
| Stool inflammation marker | Raised | Normal |
| Colonoscopy | Shows changes | Normal |
IBS causes real symptoms without visible inflammation, and its treatment is different.
Which tests confirm it?
- Stool tests: for infection, and faecal calprotectin, a protein released by inflammatory cells. A normal level makes significant bowel inflammation unlikely.
- Blood tests: for anaemia, markers of inflammation, and coeliac disease.
- Colonoscopy with tissue samples: shows where the inflammation is, how severe it is and what kind.
- Upper GI endoscopy: for the stomach and upper small intestine.
- Scans: for parts of the small intestine that endoscopes do not reach.
How is it treated?
Treatment follows the cause:
- Infection: the right antimicrobial, fluids and rest
- Inflammatory bowel disease: medicines that control the immune response, with regular monitoring
- Coeliac disease: a strict gluten-free diet
- Medicine-related: stopping or replacing the medicine, with protection for the lining
- H. pylori: a two-week combination course
What else supports healing?
Alongside the specific treatment, I look at what helps the lining to recover and stay well:
- Nutrition: enough protein, and correction of low iron, vitamin B12, folate and vitamin D
- Food pattern: home-cooked meals with less ultra-processed food; fibre adjusted to what the bowel tolerates during a flare and widened afterward
- Smoking and alcohol: both worsen gut inflammation
- Sleep and stress: poor sleep and sustained stress are linked with flares
- Careful use of painkillers: paracetamol in place of anti-inflammatory painkillers where possible
These measures support medical treatment. They do not replace it.
When should I see a doctor?
Seek care promptly for
- Blood in the stool
- Diarrhoea for more than two weeks
- Severe abdominal pain, fever or vomiting
- Six or more loose stools a day
- Weight loss or a low blood count
Questions patients ask me
Can a blood test show gut inflammation?
Blood markers rise with significant inflammation, but they are not specific to the gut. A stool calprotectin test is more direct.
Can food cause inflammation in the gut?
In coeliac disease, gluten does. For most people, no single food inflames the gut, but a diet built on ultra-processed food and low in fibre is associated with more inflammatory disease.
Does gut inflammation always mean colitis?
No. Infection is the commonest cause and passes. Persistent inflammation needs a colonoscopy to establish the diagnosis.
Can gut inflammation be present without symptoms?
Yes. In inflammatory bowel disease, the lining can remain inflamed after symptoms settle. This is why stool tests and colonoscopy are used to monitor treatment.
Sources
This page is written for patients and is based on the guidelines and studies below. It is for education and does not replace a consultation.
- American College of Gastroenterology guideline on ulcerative colitis in adults. Rubin DT et al. Am J Gastroenterol. 2019. PubMed 30840605
- European Crohn’s and Colitis Organisation guideline on medical treatment in Crohn’s disease. Torres J et al. J Crohns Colitis. 2020. PubMed 31711158
- American College of Gastroenterology guideline on irritable bowel syndrome. Lacy BE et al. Am J Gastroenterol. 2021. doi:10.14309/ajg.0000000000001036
- American College of Gastroenterology guideline on coeliac disease. Rubio-Tapia A et al. Am J Gastroenterol. 2023. PubMed 36602836
- STRIDE-II treatment targets in inflammatory bowel disease. Turner D et al. Gastroenterology. 2021. PubMed 33359090