Disclaimer: This article is not medical advice. Always seek advice from a qualified medical practitioner about your own symptoms, diagnosis, or treatment. This article is based on anonymised discussions from our group on Facebook, combined with published medical guidance.
- Why Diverticulitis Changes Your Poo
- Diverticulitis Stool Colour: What Members Say
- Mucus In Stool With Diverticulitis
- Blood In Stool: When It Is Urgent
- Diverticulitis Stool Consistency: Constipation, Diarrhoea And Everything Between
- A Practical Tip From The Group: Toilet Posture
- Using The Bristol Stool Chart To Track Your Diverticulitis Symptoms
- Diverticulitis Stool Changes: A Quick Comparison
- Frequently Asked Questions
- Is It Normal For Diverticulitis Poo To Change Colour?
- Why Is My Poo Yellow Or Mustard-Coloured During A Flare?
- Can Diverticulitis Cause Green Poo?
- Does Diverticulitis Cause Pencil-Thin Or Ribbon-Like Stools?
- Is Mucus In Stool Always A Sign Of Diverticulitis?
- When Is Blood In Stool A Medical Emergency?
- What Does Diverticulitis Poo Smell Like?
- Key Takeaways
- Stop Guessing. Start Understanding
Diverticulitis poo can look very different from person to person, and even from one flare to the next in the same person. During a flare it often becomes looser or more frequent, may carry streaks of mucus, and can range from pale yellow through to green or darker brown. Some people also notice pencil-thin stools, hard pellets, or occasional spotting of blood. A change that is new for you, or blood that does not clear up, always needs checking by a GP.
Stool changes are one of the most common things our Facebook community members ask each other about, because doctors rarely have time to explain what “normal” looks like during a flare. Below, real members describe what they have seen, alongside NHS guidance and the Bristol Stool Chart, so you know what is common and what needs urgent attention.
Why Diverticulitis Changes Your Poo
Diverticulitis is inflammation or infection in one or more of the small pouches (diverticula) that can form in the wall of the large intestine. According to the NHS, the condition causes tummy pain, a change in bowel habit, and sometimes blood or mucus in your poo. Inflammation irritates the bowel lining, which is why colour, consistency and frequency can all shift during a flare, then settle back down once the inflammation clears.
Research published on PubMed Central found that roughly 40% of people still had mild abdominal pain or a changed bowel habit a year after a confirmed episode of diverticulitis, which matches what many of our members describe: bowel habits do not always snap straight back to how they were before the flare.
Diverticulitis Stool Colour: What Members Say
Colour is the question that comes up again and again in the group. Members describe everything from pale brown to mustard yellow, green, and darker shades. The table below sets out what each colour tends to mean, based on member experience and NHS/WebMD guidance.
Colour | What It Often Means | Should You Worry? |
Normal to pale brown | Typical, healthy colour | No, this is the baseline most people aim for |
Mustard or pale yellow | Can happen during a flare, or with excess mucus or fat in the stool | Mention it at your next GP review if it persists |
Green | Food moving through the gut quickly, or diet (leafy greens) | Usually settles within a few days |
Very dark brown or black | Can be diet or iron tablets, but can also mean bleeding higher up the gut | See a GP promptly if you have not eaten anything that explains it |
Bright red streaks | Fresh bleeding, often from the back passage | Get medical advice the same day, sooner if bleeding is heavy |
Not to be graphic, but what does your poo look like with diverticulitis? Mine has a yellowy colour to it now, with quite a bit of mucus. Sometimes when I try to push it’s mucus only, sometimes it’s normal, and sometimes it’s really hard pellets. Other times it’s diarrhoea, but over the past year it has mostly been that lighter yellowy colour.
– Pauline, Skegness
My poo changes colour every time I go. I don’t worry about it.
– Margaret, Ludlow
Mine is a mustard colour. Lovely.
– Brenda, Kirkcaldy
Several members made the same point Margaret did: colour on its own, without pain, bleeding or other new symptoms, is rarely a reason to panic. Diet, hydration and how quickly food has moved through your gut all play a part. The exception is black, tarry stool or bright red blood, which should always be checked.
Mucus In Stool With Diverticulitis
Mucus is a sticky, jelly-like substance your intestines produce naturally to help stool pass smoothly. A small, occasional amount is normal. During diverticulitis, inflammation in the bowel lining can increase mucus production, so more of it shows up in your poo. Frimley Health NHS Foundation Trust lists mucus or blood in the stool as one of the most common symptoms of diverticular disease.
Mine has never been yellowy. In my experience, mucus is more a sign that I am constipated than anything else.
– Sheila, Torquay
Not every member agrees on what causes their mucus, and that is expected. Some link it to constipation, others to a flare, and others simply to their underlying condition. This is a good example of why tracking your own pattern in a food and symptoms diary is more useful than comparing yourself to any single description online.
Blood In Stool: When It Is Urgent
Blood is the one change in this article that always deserves a proper answer, not reassurance. Several members described being sent for tests, scans or hospital admission after noticing blood alongside cramping and mucus.
I have been in a flare for 23 days, with blood and mucus in my stool. I ended up in A&E, had an abdominal scan, and a stool test booked. The pain was severe cramping down my left side, and I was passing mushy, loose poo with fresh blood even after wiping.
– Vera, Dumfries
I managed a watery, mushy stool, but blood was present, so I was sent up to the ward.
– Norma, Consett
These are exactly the symptoms the NHS asks you to act on quickly. Their guidance is direct:
Get Urgent Advice From NHS 111 Or A GP If:
- There is blood or slime (mucus) in your poo
- Your tummy pain is getting worse or does not go away
- You have a high temperature, or feel hot, cold or shivery
- You keep being sick and cannot keep fluids down
- You have diarrhoea for more than 7 days, or are being sick for more than 2 days
Call 999 Or Go To A&E Immediately If:
- You have severe tummy pain and are vomiting, have a swollen tummy, or cannot poo or pass wind
- You are bleeding heavily from your bottom
- You feel confused, look pale or blotchy, have a very high or low temperature, or are breathless, which can be signs of sepsis
This guidance comes directly from the NHS diverticular disease and diverticulitis page. Keep it bookmarked. It is worth reading in full before a flare happens, not during one.
Diverticulitis Stool Consistency: Constipation, Diarrhoea And Everything Between
Consistency changes just as much as colour. Some members swing between constipation and diarrhoea in the same week, while others settle into one pattern for months at a time.
My poo varies in colour from a very pale brown to a normal colour. I have been through what I would call rabbit-dropping stools, right through to diarrhoea with mucus, sometimes looking like a thin sausage. I did not have a normal stool for a few months.
– Janet, Ayr
Pencil-thin or ribbon-like stools come up often enough in the group to deserve their own mention.
I have read here that it is possible for diverticulosis to cause pencil-thin stools. I take a stool softener daily to avoid constipation, which can trigger a flare, but if I use too much stool softener I get thin stools, and if I do not use enough, they are quite normal. I never see any blood, but these thin stools often come with the classic left-side pain.
– Barbara, Wrexham
I get thinner stools most of the time, no blood, but I get pain right across my stomach, from left to right.
– Norma, Consett
Narrowed stools can simply reflect swelling and spasm in an inflamed section of bowel, which temporarily narrows the passage. If pencil-thin stools become your new normal, or come with weight loss, it is worth asking your GP to rule out other causes rather than assuming it is diverticulitis alone.
Green, loose stools also feature regularly during flares.
I am just getting over another attack of diverticulitis. My poo this time was very loose and green, and I lost 6lb in five days.
– Doreen, Neath
Just diagnosed. Three days of fasting, then antibiotics. Greenish poo. Brown is the right colour, isn’t it?
– Colin, Redditch
Green stool during a flare is usually food moving through the gut faster than normal, which does not give the body as much time to break down bile pigment. It typically settles as the flare calms down. If it persists for more than a week or two after you feel better, mention it to your GP.
A Practical Tip From The Group: Toilet Posture
Not everything the group shares is about what stool looks like. Several members also shared what has actually helped them pass a hard bowel movement more comfortably.
I have been using the NHS advice on how to position yourself on the toilet, which is raising your knees slightly higher than your hips. Struggling with a hard bowel movement, this has been a game changer and has helped me so much, otherwise I fear I would be so constipated. Do look this up. You can use a child’s step stool, or anything that works for you.
– Audrey, Rhyl
Using The Bristol Stool Chart To Track Your Diverticulitis Symptoms
One member summed up why this chart matters better than any textbook:
Many of us have a mixture of constipation and diarrhoea, and are glad when we get a normal stool. Check the Bristol Stool Chart.
– Iris, Whitby
The Bristol Stool Chart gives you a shared language with your GP, so you can describe your poo accurately without needing to bring in a sample. Types 3 and 4 are considered the healthy target. Types 1 and 2 point towards constipation, and types 5 to 7 point towards looser stools or diarrhoea.
Type | Description | What It Suggests |
Type 1 | Separate hard lumps, like nuts, hard to pass | Severe constipation |
Type 2 | Sausage-shaped but lumpy | Mild constipation |
Type 3 | Sausage-shaped with cracks on the surface | Normal |
Type 4 | Smooth, soft sausage or snake shape | Normal, ideal type |
Type 5 | Soft blobs with clear edges | Lacking fibre, leaning towards loose |
Type 6 | Fluffy, mushy pieces with ragged edges | Mild diarrhoea |
Type 7 | Entirely liquid, no solid pieces | Severe diarrhoea |
Tracking which type you see, alongside colour, mucus, blood and pain, is far more useful over time than a single snapshot. Our free food and symptoms diary also lets you log your bowel habits each day, so patterns become obvious rather than guesswork, and you have something concrete to show your GP or gastroenterologist.
Diverticulitis Stool Changes: A Quick Comparison
Feature | Diverticulosis (No Flare) | Diverticulitis Flare |
Typical Bristol type | Types 3 to 4, usually steady | Types 1 to 2 or 6 to 7, often changeable |
Mucus | Occasional, small amounts | More noticeable, sometimes on its own |
Blood | Uncommon, always worth checking | Can appear with cramping, needs urgent checking |
Colour | Normal brown | Can shift to yellow, green or darker shades |
Pain pattern | Little to none | Constant, often lower left-side pain |
Frequently Asked Questions
Is It Normal For Diverticulitis Poo To Change Colour?
Yes. Colour changes are common during a flare and usually settle down once the inflammation eases. Black, tarry stools or bright red blood are the exceptions that always need medical attention.
Why Is My Poo Yellow Or Mustard-Coloured During A Flare?
A yellowy or mustard colour is often linked to mucus, faster gut transit, or dietary fat not being fully broken down. Several members describe this pattern lasting for months at a time without other worrying symptoms, but it is still worth mentioning at your next GP review if it does not settle.
Can Diverticulitis Cause Green Poo?
Yes. Green stool is usually a sign that food is moving through your gut more quickly than usual, which is common during a flare or after a course of antibiotics. It normally returns to brown within a few days once things settle.
Does Diverticulitis Cause Pencil-Thin Or Ribbon-Like Stools?
It can. Inflammation and spasm can temporarily narrow part of the bowel, which narrows the stool passing through it. If this becomes persistent, or comes with weight loss or a new pattern that does not fit your usual flares, ask your GP to rule out other causes.
Is Mucus In Stool Always A Sign Of Diverticulitis?
No. A small amount of mucus is a normal part of healthy digestion. More noticeable or frequent mucus can be linked to diverticulitis, constipation, or other bowel conditions, so it is best assessed alongside your other symptoms rather than on its own.
When Is Blood In Stool A Medical Emergency?
Any blood in your stool should be checked by a GP or NHS 111. It becomes an emergency, meaning you should call 999 or go to A&E, if the bleeding is heavy, or if it comes with severe pain, vomiting, a swollen tummy, or signs of confusion or a very high or low temperature. Full detail is on the NHS website.
What Does Diverticulitis Poo Smell Like?
Many members describe a stronger, more unpleasant smell during a flare, which fits with the inflammation and infection that diverticulitis involves. Smell alone is rarely a reason to seek urgent help, but combined with fever or worsening pain, it is another signal to contact your GP.
More Reading
Key Takeaways
- Diverticulitis poo can range from pale yellow to green, and consistency can shift between constipation and diarrhoea, often within the same week.
- Mucus is common during a flare and is not usually a reason to worry on its own.
- Blood in your stool always needs checking. Heavy bleeding, severe pain or a high temperature need urgent NHS 111 advice or 999.
- Pencil-thin stools can happen when inflammation narrows part of the bowel, and should be mentioned to your GP if they persist.
- The Bristol Stool Chart gives you a simple, shared way to describe your poo to a GP or gastroenterologist.
- Tracking colour, consistency, mucus and pain in a food and symptoms diary makes patterns clearer than comparing yourself to a single description online.
If your bowel habits keep changing and you want to understand your own pattern rather than guess, start a free food and symptoms diary today, or share your experience with others who understand in our forums. You are not alone in checking the colour of your poo before anything else in the morning. Many of our members do exactly the same.
Disclaimer: This article is not medical advice. Always seek advice from a qualified medical practitioner about your own symptoms, diagnosis, or treatment. This article is based on anonymised discussions from our group on Facebook, combined with published medical guidance.
