Microscopic Colitis 

Key points 

  • Microscopic colitis is a less common inflammatory bowel disease (IBD) that causes inflammation in the large intestine. 
  • Microscopic colitis affects the inner lining of the large intestine (colon). 
  • Causes of microscopic colitis seem to be related to gut damage from viruses, bacteria or medicine. 
  • There is no cure for microscopic colitis but it can be managed well with medicine. 

About microscopic colitis

What is microscopic colitis? 

Microscopic colitis is a type of inflammatory bowel disease (IBD) that can cause inflammation in the large intestine (colon). Inflammation can cause redness, swelling and pain, and is the body’s response to injury or irritation. This disease is not as common as the two main types of IBD, Crohn’s disease and ulcerative colitis, and is less well recognised. 

The gut has many layers and microscopic colitis affects the inner layer of the intestines. There are two types of microscopic colitis. How the disease affects this inner layer of the gut decides which of the two it is: 

  • Lymphocytic colitis (LC) – where the inner lining has more white blood cells (lymphocytes) than usual.  
  • Collagenous colitis (CC) – where the inner lining has a thicker layer of collagen, a protein important in providing structure in the body, than usual.  

Although they look different under the microscope, symptoms and treatment are the same. However slightly more people have LC, and women are more likely to have CC. Some people may even have both types of microscopic colitis, but at different times.  

What does living with microscopic colitis mean for me? 

Microscopic colitis is a chronic condition which means that it is for life. Symptoms of the disease can have a real impact on life. The unpredictable nature can mean some days aren’t good and you can feel that you no longer know your own body. This can make going out with friends, work and planning activities really difficult.  

Coping with these symptoms may make you feel isolated and low but with careful planning and a strong support network you can take control of your own health. 

What is the cause of microscopic colitis? 

What causes microscopic colitis is still unknown but it seems to be related to damage to the gut caused by: 

  • Medications that can irritate the lining of the colon. 
  • Bacteria that produce toxins that irritate the lining of the colon. 
  • Viruses that trigger inflammation. 
  • Autoimmune disease associated with microscopic colitis, such as rheumatoid arthritis, celiac disease or psoriasis. Autoimmune disease occurs when your body’s immune system attacks healthy tissues. 
  • Bile acid not being properly absorbed and irritating the lining of the colon. 

Other factors such as genes, gender and smoking may also have a role to play in causing microscopic colitis. 

Is there a cure for microscopic colitis? 

There is no cure for microscopic colitis but medicine and in some rare cases, surgery, can reduce or remove symptoms. Some people even recover without medicine as the disease may improve with time.  

Microscopic colitis has no effect on life expectancy and doesn’t make you more likely to get colon cancer. Most people with the disease go on to lead happy and fulfilling lives. 

As you learn to manage the disease you will be able to travel around the world, form healthy relationships, eat out, exercise and have a career you enjoy. Microscopic colitis doesn’t mean you have to stop doing the things you love. 

Microscopic Colitis Symptoms 

Key points 

  • Watery diarrhoea is the main symptom of microscopic colitis. 
  • Diarrhoea will often come suddenly and without warning. 
  • Other common symptoms include tummy pain, bloating and fatigue. 

What are the symptoms of microscopic colitis? 

The main symptom of microscopic colitis is ongoing watery diarrhoea. This is where you pass watery or loose poo more than three times a day for longer than four weeks. For some people this can be as many as fifteen times during the day and night. It may begin suddenly or gradually, can happen at any time and may be every time you go to the toilet, or only now and then.  

The diarrhoea may:  

  • be sudden – you may not always reach the toilet in time  
  • be explosive – this is when your rectum has more watery poo and gas than it can hold and it expels the poo with lots of force, often loudly  
  • happen several times a day and at night 

There usually isn’t any blood in the poo.  

Other symptoms can include:  

  • pain in the tummy area – which may be cramping or dull  
  • fatigue or extreme tiredness, this may be caused by getting up at night to go to the toilet, but many people experience this even if they sleep through the night  
  • joint pain  
  • bloating and wind 

Microscopic Colitis Diagnosis 

Key points 

  • People who are diagnosed with microscopic colitis often have another condition related to the immune system. 
  • Inflammation caused by microscopic colitis cannot be seen with the naked eye – tissue from the gut must be examined under a microscope. 
  • Many people with microscopic colitis also have bile acid malabsorption (BAM) so you may also be tested for this condition. 

How do I know if I have microscopic colitis? 

Microscopic colitis is less well known by both health professionals and the general public so it can be difficult to get a diagnosis. 

People who are more likely to get the disease are over 50 years old and often also have an autoimmune condition. 

These include:  

  • Type 1 diabetes 
  • thyroid disease 
  • coeliac disease 
  • rheumatoid arthritis 

Bile acid malabsorption (BAM)  

Around 4 out of 10 people with microscopic colitis also have BAM. Bile salts help you to digest fats. When you eat a meal, especially with fat in it, these bile salts are released from your liver and gall bladder into the upper part of your gut. They help to digest the food as it travels through your small intestine. When the bile salts reach the far end of this, they are mostly absorbed back into your body and return to your liver in the bloodstream.  

Bile acid malabsorption happens when the gut can’t direct bile acid back to the liver. It’s thought that this irritates the lining of the large intestine (colon) and means that your body doesn’t absorb water properly. This means you produce large amounts of watery poo. 

All of this will be taken into account by your doctor before a moving onto the medical tests: 

Colonoscopy with biopsy  

In microscopic colitis, changes in the gut can only be seen under the microscope. So, to diagnose the condition a small tissue sample (biopsy) is taken from the colon when you have a colonoscopy. This is then looked at under a microscope.  

In a colonoscopy, a long flexible tube (about the thickness of your little finger) with a bright light and camera at its tip is inserted through your anus. This allows the doctor to have a look at the lining of your colon and painlessly remove small pieces of tissue to look at under a microscope. A few samples are usually taken from different parts of the colon.  

The doctor won’t be able to see any visible signs of inflammation when they look at your colon and rectum. This is different from Crohn’s or ulcerative colitis when inflammation or ulcers can be seen.  

Other tests you may have  

You may have a test for bile acid malabsorption. You’ll be given a small capsule of a synthetic bile salts to swallow which contains a small amount of harmless radioactive material known as SeHCAT. You’ll then have a scan and another one a week later. These will measure the absorption of the radioactive bile salts.  

Delay in getting a diagnosis  

It may take some time to get a diagnosis of microscopic colitis, and this can be frustrating.  

This may be because:  

  • A poo test (faecal calprotectin) isn’t usually helpful – this finds evidence of inflammation in the gut, but with microscopic colitis levels are often quite low. 
  • Your colon and rectum will look normal at colonoscopy – it is vital to take biopsies to find microscopic colitis.  
  • Symptoms may be similar to other conditions such as irritable bowel syndrome (IBS) or coeliac disease which doctors may be more familiar with. 

Microscopic Colitis Treatment 

Key points 

  • There are some commonly used medicines that badly affect microscopic symptoms so you should always talk with your doctor about what you are using. 

What kind of treatments are there for microscopic colitis? 

Before you’re offered any treatment for microscopic colitis your doctor will review the medicines you already take for other conditions.  

Medicines that may trigger microscopic colitis include:  

  • non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, diclofenac  
  • some proton pump inhibitors (PPIs) such as omeprazole and lansoprazole used to reduce stomach acid  
  • selective serotonin reuptake inhibitors (SSRIs) used to treat depression  
  • asprin  
  • acarbose for diabetes 
  • ranitidine for indigestion and heart burn  
  • ticlopidine for blood conditions 
  • statins for cholesterol control 

Many of these medicines can also cause diarrhoea as a side effect. But if you are taking any of these do not stop taking them until you’ve talked to your doctor.  

Lifestyle changes  

Cutting down alcohol and caffeine can be helpful in reducing diarrhoea. It’s often useful to keep a record of when you stop or cut down and how your symptoms change, such as in a food diary.  

  • Try cutting down on caffeine – drink decaffeinated tea, coffee, soft drinks or water and reduce the amount of chocolate you eat.  
  • Cut down alcohol – drinking less has been shown to help symptoms.  
  • Stop smoking – smoking increases the risk of microscopic colitis, and people who smoke have symptoms which are worse and less likely to get better with treatment. Your GP practice can offer support with stopping smoking.  

Medication for microscopic colitis includes several options depending on how serious your symptoms are. Surgery is rarely needed to treat the disease but there are some options available if medication isn’t doing the job. 


If you have mild microscopic colitis, medicines to stop diarrhoea, such as loperamide, can be effective. These slow down muscle contractions of the gut which makes food move through more slowly and allows more water to be absorbed. Poo becomes firmer and less urgent. They can also help to control symptoms whilst other medications take time to work.  

Bile acid sequestrants  

These include colestyramine, colestipol or colesevelam. If microscopic colitis is related to bile acid malabsorption (BAM), or you continue to have diarrhoea despite other treatment, you may be offered this type of medicine. These bind to the bile acids in your gut and help to improve symptoms of diarrhoea. It has been suggested that this may be effective even where BAM isn’t present.  


This steroid has been found to be an effective treatment if you have moderate to severe microscopic colitis. Around 8 out of 10 people have been shown to improve when taking this medicine and there are usually few side effects.  

The normal dose is 9mg of budesonide a day for 6 to 8 weeks. You may also be offered loperamide to control the diarrhoea whilst the budesonide gets your condition under control. Your symptoms may start to get better within one or two days but for some people it can take around three and six weeks.  

Over half of people on budesonide find their symptoms come back when the treatment stops. If this happens to you a lower dose may be tried, and this could be continued for up to a year. As with all steroids this isn’t usually a long-term option.  

Most people get better with these approaches but if they don’t work for you other treatments may be tried  

Biologic Medicines 

Infliximab and adalimumab have been shown in small studies to improve symptoms for some people where budesonide hasn’t been effective. Small studies also suggest that vedolizumab could be helpful. These medicines are taken by infusion or injection. 


Azathioprine and mercaptopurine have been shown to be effective for some people where budesonide hasn’t worked. Find out more in Azathioprine and Mercaptopurine.  

Diet with microscopic colitis is different for everyone. There isn’t evidence that specific foods affect some people with microscopic colitis but you may find that some foods are a trigger for you. Fatty, spicy and high fibre foods make some people feel worse, but everyone is different. Many people ask: 

Should I avoid gluten? – People with microscopic colitis are more than 50 times more likely than the general population to have coeliac disease. This means you’re not able to digest a type of protein called gluten, which is found in wheat, barley and rye. To find out if you need to avoid gluten, your doctor will do a blood test to check for this. If your blood test is positive, you may also have an upper gastrointestinal endoscopy to confirm.  

Should I avoid dairy products? – If your diarrhoea is worse after eating dairy, you may have trouble digesting lactose – the type of sugar found mainly in milk, cheese and other dairy products. Keeping a food diary to see how you feel can help you to find out if this is the case for you. Sometimes a simple breath test is used to find out if you’re lactose intolerant.  

Talk to your doctor or dietitian before making any major changes to your diet. They can help you plan how to avoid dairy products or gluten while still getting the nutrients you need.  

Who to talk to if you’re worried 

Our Helpline takes many calls from people with microscopic colitis so you’re not alone. We can’t advise but it may help to talk through your worries. Your doctor will support you and you can also ask for support from our IBD nurse-led service NurseLine


Drugs such as NSAIDs and proton pump inhibitors (PPIs) are implicated as the cause in up to half of cases of microscopic colitis. 

Around 4 in 10 people with microscopic colitis also have a condition caused by the immune system attacking other parts of the body (autoimmune condition).   

1 in 4 people who are diagnosed with microscopic colitis are under 25.