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Health condition

Inflammatory bowel disease, Crohn, ulcerative colitis and IBD-U in one place.

IBD is a lifelong immune-mediated bowel disease - but modern biologics, JAK inhibitors and S1P modulators mean deep remission is a realistic goal.

Jump to treatment

Prefer the classic overview? See our companion guide at /conditions/inflammatory-bowel-disease.

A radiographer guides a patient onto the bed of an advanced 3 Tesla MRI scanner in a London imaging suite

Why trust this guide

  • 01

    Editorial team

    Written by our editorial team from the UK sources listed on each page.

  • 02

    Sourced from guidance

    Checked against NICE, the British Society of Gastroenterology (BSG) and ECCO consensus statements you can see at the end.

  • 03

    Current for 2026

    Reflects the modern IBD toolkit including advanced biologics, JAK inhibitors and S1P receptor modulators.

Key facts

IBD at a glance.

The essentials, in plain English - what IBD is, the main subtypes, and how it is diagnosed and treated in the UK today.

  • What it is

    A group of chronic immune-mediated bowel diseases - principally Crohn disease, ulcerative colitis and IBD-unclassified (IBD-U).

  • Two main types

    Crohn can affect any part of the gut from mouth to anus; ulcerative colitis is limited to the colon and rectum.

  • IBD-U

    Around 5 to 10 per cent of colonic IBD does not fit neatly into Crohn or UC at diagnosis - reclassification may follow.

  • Diagnostic gold

    Ileocolonoscopy with biopsies, cross-sectional imaging (MRI enterography) and faecal calprotectin.

  • Modern therapy

    Biologics, small-molecule JAK inhibitors and S1P modulators have transformed outcomes for moderate-to-severe disease.

  • MDT-led care

    IBD is managed by a specialist multidisciplinary team - gastroenterologist, IBD nurse, radiologist, surgeon and dietitian.

Why this guide matters

Modern IBD care is a partnership.

IBD is a lifelong condition, but the last decade has transformed the toolkit. The three points below shape everything else on this page.

  • Treat-to-target, not to feel-fine

    Symptom control is not enough - the target is endoscopic and biomarker remission (mucosal healing, normal calprotectin, normal CRP).

  • Advanced therapy earlier

    For moderate-to-severe disease, waiting years before biologics or small molecules costs bowel and quality of life. Early escalation changes trajectory.

  • The MDT is your safety net

    Gastroenterologist, IBD nurse, radiologist, colorectal surgeon and dietitian - IBD is best delivered by a co-ordinated team, not a solo clinician.

How the diagnosis is made

From first symptoms to a confirmed IBD plan.

The steps a UK GP and gastroenterology team will normally follow, in order - so you know what to expect and why.

  1. 01

    Assessing

    History and symptoms

    Bloody diarrhoea, urgency, abdominal pain, weight loss, fatigue and extra-intestinal features - a careful history sets the direction.

  2. 02

    Assessing

    Faecal calprotectin

    A stool marker of gut inflammation - highly sensitive and used to separate IBD from irritable bowel syndrome.

  3. 03

    Assessing

    Bloods and infection screen

    FBC, CRP, ferritin, albumin, U&E, LFTs plus stool cultures and C. difficile to exclude infection.

  4. 04

    Confirming

    Ileocolonoscopy with biopsies

    The diagnostic gold standard - endoscopic pattern plus histology distinguishes Crohn, ulcerative colitis and IBD-U.

  5. 05

    Confirming

    MRI enterography

    Preferred cross-sectional imaging for small-bowel Crohn - maps disease extent, strictures, fistulae and abscesses without radiation.

  6. 06

    Preparing

    Disease phenotype and risk

    Montreal classification of location, behaviour and severity guides how quickly to escalate to advanced therapy.

  7. 07

    Preparing

    Baseline for advanced therapy

    TB and hepatitis screen, vaccinations, TPMT for thiopurines - the groundwork before biologics or small molecules start.

Typical timeline: calprotectin and bloods in days, endoscopy and imaging within weeks.

Symptoms

What IBD actually feels like.

Bloody diarrhoea in ulcerative colitis, cramping and perianal disease in Crohn - plus the extra-intestinal features that catch clinicians out.

  • Bloody diarrhoea

    A cardinal symptom of ulcerative colitis - usually with urgency and rectal mucus.

  • Abdominal pain

    Cramping right-lower-quadrant pain in ileal Crohn; left-sided pain and tenesmus in UC proctitis.

  • Weight loss and fatigue

    Malabsorption, poor appetite and chronic inflammation drive fatigue, iron deficiency and unintended weight loss.

  • Perianal disease

    Fissures, abscesses and fistulae are hallmarks of Crohn - MRI pelvis is the imaging of choice.

  • Strictures and obstruction

    Fibrotic narrowing in long-standing Crohn - bloating, colicky pain and vomiting warrant urgent imaging.

  • Extra-intestinal features

    Joints, eyes, skin and liver can all be affected - arthritis, uveitis, erythema nodosum and primary sclerosing cholangitis.

  • Growth failure in young people

    In children and adolescents, delayed puberty or falling growth centiles may be the first clue to Crohn.

  • Red flag - acute severe colitis

    Truelove and Witts criteria - more than six bloody stools daily with systemic upset needs hospital admission.

Treatment

How IBD is treated in the UK.

A stepped ladder from 5-ASA and steroid induction, through immunomodulators and biologics, to JAK inhibitors, S1P modulators and surgery.

  • 5-aminosalicylates (5-ASA)

    Mesalazine and sulfasalazine - foundational for mild-to-moderate ulcerative colitis; limited role in Crohn disease.

  • Corticosteroids

    Prednisolone or budesonide MMX for induction only - not for maintenance because of long-term harm.

  • Immunomodulators

    Azathioprine, mercaptopurine and methotrexate - used for steroid-sparing maintenance, guided by TPMT and monitoring bloods.

  • Anti-TNF biologics

    Infliximab and adalimumab - the established first-line biologic class for moderate-to-severe Crohn and UC.

  • Anti-integrin and anti-IL-23

    Vedolizumab (gut-selective), ustekinumab, risankizumab and mirikizumab - powerful options for anti-TNF failures or first-line in the right patient.

  • JAK inhibitors

    Tofacitinib, upadacitinib and filgotinib - oral small molecules for moderate-to-severe UC and, for upadacitinib, Crohn disease.

  • S1P receptor modulators

    Ozanimod and etrasimod - oral options for moderate-to-severe UC that sequester lymphocytes from the gut.

  • Surgery

    Ileocaecal resection in limited Crohn, subtotal colectomy in acute severe UC and ileal-pouch anal anastomosis for definitive UC surgery.

For dedicated treatment pathways see our upadacitinib IBD page, our risankizumab IBD page, IV iron therapy for iron-deficiency anaemia, and our bowel function guide for continence and evacuation problems.

What this guide is based on

The sources behind every claim on this page.

UK national guidance, BSG standards and ECCO consensus, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your gastroenterologist and IBD nurse know your history and can tell you which parts apply to you. If in doubt, get seen.

  • NICE. Crohn disease: management (NG129).

  • NICE. Ulcerative colitis: management (NG130).

  • British Society of Gastroenterology. IBD guidelines and standards of care.

  • ECCO. Consensus guidelines on Crohn disease and ulcerative colitis.

  • MHRA and NICE. Technology appraisals for advanced IBD therapies including upadacitinib, risankizumab, ozanimod and etrasimod.

Red flags

When IBD needs urgent attention.

Most IBD is managed as an outpatient. These are the situations that need same-day or emergency review.

  • Acute severe ulcerative colitis

    Truelove and Witts criteria - more than six bloody stools daily plus systemic upset. Emergency admission for IV steroids, VTE prophylaxis and rescue therapy planning.

  • Toxic megacolon

    Colonic dilatation over 6 cm with systemic toxicity - a surgical emergency requiring urgent colorectal review.

  • Bowel obstruction

    Progressive bloating, colicky pain, vomiting and constipation in Crohn - needs imaging and a surgical opinion.

  • Perianal sepsis

    Perianal pain, fever and induration in Crohn suggest an abscess - MRI pelvis and drainage under a colorectal surgeon.

  • Uncontrolled bleeding

    Ongoing haemorrhage with haemodynamic change is rare but requires transfusion, endoscopic assessment and surgical stand-by.

  • New venous thromboembolism

    IBD flares roughly double VTE risk - unexplained calf pain or breathlessness should prompt urgent assessment.

  • Dysplasia or colorectal cancer

    Long-standing colitis raises colorectal cancer risk - BSG-guided surveillance colonoscopy and biopsies are essential.

  • Opportunistic infection on therapy

    Fever, cough or new symptoms on biologics, JAK inhibitors or steroids - assess urgently for TB reactivation, herpes zoster and CMV colitis.

  • IBD complications

    For a broader look at strictures, fistulae, nutritional loss and cancer risk, see our dedicated guide to IBD complications.

Living with it

A lifelong condition, with a clear plan.

Four things that make the biggest difference day to day - knowing your team, monitoring calprotectin, eating well and escalating early when you need to.

A quiet reminder

Deep remission is the goal, not just fewer symptoms.

Symptom control matters, but so does what a colonoscope and a calprotectin show - treat-to-target changes long-term outcomes.

  1. 01 Team

    Know your IBD team

    Your gastroenterologist and IBD nurse specialist are your first call - most units have a nurse-led advice line for flares.

  2. 02 Monitor

    Track calprotectin and symptoms

    Symptoms alone under-call inflammation - regular faecal calprotectin and treat-to-target reviews catch quiet disease.

  3. 03 Nutrition

    Feed the gut sensibly

    Iron, B12, folate and vitamin D often need topping up. A specialist IBD dietitian can help around strictures and post-resection.

  4. 04 Escalate

    Do not settle for smouldering IBD

    Modern biologics and small molecules mean mucosal healing is a realistic goal - ask about advanced therapy if you are still symptomatic.

Frequently asked

Everything we get asked about IBD.

Quick answers on Crohn versus UC, biologics, JAK inhibitors, surgery and monitoring.

  • What is inflammatory bowel disease (IBD)?

    IBD is a group of chronic immune-mediated bowel diseases - principally Crohn disease and ulcerative colitis, plus IBD-unclassified when the picture overlaps. It is different from irritable bowel syndrome (IBS), which is a functional disorder without inflammation.

  • How is IBD different from IBS?

    IBD causes measurable inflammation in the gut, ulceration on colonoscopy and complications such as strictures, fistulae and dysplasia. IBS causes real symptoms - pain, bloating, altered bowel habit - without inflammation. Faecal calprotectin and colonoscopy are the tests that separate the two.

  • How is Crohn disease different from ulcerative colitis?

    Ulcerative colitis affects only the colon and rectum with continuous mucosal inflammation. Crohn disease can affect any part of the gut from mouth to anus, is often patchy and transmural, and can produce strictures and fistulae. Some patients have colonic IBD that does not fit either box - that is IBD-unclassified. See our dedicated guides to Crohn disease and ulcerative colitis for detail.

  • What are the newer treatments for IBD?

    The last five years have added several advanced options - anti-IL-23 biologics (risankizumab, mirikizumab), JAK inhibitors (upadacitinib, filgotinib) and S1P receptor modulators (ozanimod, etrasimod). Choice depends on disease type, severity, previous therapy and comorbidities, and is a shared decision with your IBD team.

  • Will I need surgery for IBD?

    Not everyone - modern medical therapy has reduced surgery rates but around half of Crohn patients and 15 to 20 per cent of ulcerative colitis patients will eventually need an operation. Ileocaecal resection in limited Crohn and ileal-pouch anal anastomosis in UC are the classic procedures. Early surgery is now considered in the right patients rather than a last resort.

  • What monitoring will I need?

    Regular clinical review, faecal calprotectin, bloods (FBC, CRP, ferritin, albumin, LFTs), drug-level monitoring for biologics and thiopurines, and BSG-guided surveillance colonoscopy for long-standing colitis. Vaccinations, bone health and mental-health support are part of the IBD MDT plan.

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