This article is not medical advice. Medical advice should always be sought from a qualified medical practitioner.
- What Does A Diverticulitis Flare Up Feel Like?
- How Is Diverticulitis Different From Diverticulosis?
- Why Are Diverticulitis Symptoms Sometimes Missed Or Dismissed?
- What Symptoms Continue Between Flares?
- When Do Diverticulitis Symptoms Need Emergency Care?
- How Do Members Manage Flare Up Symptoms?
- Frequently Asked Questions
- Does Diverticulitis Always Cause A Fever?
- Can Diverticulitis Cause Bloating Without Pain?
- How Long Does A Diverticulitis Flare Up Last?
- Is It Safe To Take Ibuprofen During A Flare Up?
- Key Takeaways
- Stop Guessing. Start Understanding.
- Stop Guessing. Start Understanding
This article is based on anonymised discussions from our Diverticulitis Club Facebook group, combined with guidance from the NHS and Mayo Clinic.
A diverticulitis flare up causes sudden pain in the lower left side of the abdomen, together with fever, nausea, tenderness, bloating, and a change in bowel habit such as constipation or diarrhoea. The pain is usually the symptom that sends people to their GP or the emergency department, because it tends to arrive quickly and does not ease with rest.
- Abdominal pain, usually in the lower left side
- Bloating and abdominal tenderness
- Nausea and vomiting
- Fever and chills
- Constipation or diarrhoea
- Rectal bleeding or mucus, which always needs medical review
A flare up is more than a sudden, severe inflammation or infection in one or more diverticula. It is a painful, debilitating experience that can leave someone feeling helpless and frustrated. Tracking symptoms in a food and symptoms diary helps members and their doctors spot patterns over time, rather than relying on memory during a flare.
What Does A Diverticulitis Flare Up Feel Like?
Members describe the pain of a flare up as sharp and constant rather than a dull ache, often centred on the lower left abdomen. Nausea, chills and a swollen, tender stomach commonly arrive alongside it, and bowel habits can swing to either constipation or diarrhoea within the same flare.
“With my first flare, I went six weeks barely able to eat more than a cracker. Every time I ate, it felt like glass going down. The nausea came first, and my stomach was so bloated it was agony.”
- Wendy, Sheffield
“The pain from the diverticulitis itself was bad enough, but once it perforated, it was on another level entirely. It was on my lower left side and nothing touched it.”
– Diane, Coventry
This matches Mayo Clinic’s description of diverticulitis pain as sudden and intense, though it notes the pain can also start mild and gradually worsen over a day or two.
How Is Diverticulitis Different From Diverticulosis?
Diverticulosis and diverticulitis are frequently confused, including by members who were diagnosed years apart from each condition. Diverticulosis is simply the presence of small pouches, called diverticula, in the wall of the colon. Most people with diverticulosis have no symptoms at all. Diverticulitis is what happens when one or more of those pouches becomes inflamed or infected, and this is what produces the classic flare up symptoms described in this article (NHS inform; Mayo Clinic).
“Diverticulosis is what shows up before diverticulitis develops. Doctors sometimes treat it as no big deal, but they should still tell you about it.”
– Fiona, Belfast
Feature | Diverticulosis | Diverticulitis |
What it is | Small pouches (diverticula) in the colon wall | One or more pouches become inflamed or infected |
Typical symptoms | Usually none; occasionally mild bloating or constipation | Sudden lower left pain, fever, nausea, bowel changes |
How common | Very common with age; most people over 70 have some diverticula | Develops in a minority of people who have diverticulosis |
Usual next step | Often needs no treatment beyond a high-fibre diet | Usually needs antibiotics, diet changes, or hospital care |
Why Are Diverticulitis Symptoms Sometimes Missed Or Dismissed?
A recurring theme in the Facebook group is diagnoses that sat unmentioned in scan reports for months or years. Several members only learned they had diverticulitis after a second scan, a chance comment from a different clinician, or after asking directly to see their own imaging reports.
“After three years of tests that all came back normal, a doctor in urgent care finally told me plainly: you have diverticulitis. It had been on a CT scan report the whole time, and nobody had told me.”
– Sandra, Leeds
This experience is common enough in the group that many members now recommend requesting copies of imaging and blood test reports directly, rather than waiting for a follow-up appointment that may not happen.
What Symptoms Continue Between Flares?
Bloating is the symptom members raise most often outside of an active flare. Many describe a stomach that swells through the day even when eating carefully, and several say the visible swelling has been mistaken by others for pregnancy.
“I’ve had it for years and I’m sick of people saying I look six months pregnant. A nurse once pressed my stomach laughing, with no idea how much pain it caused.”
– Angela, Manchester
Persistent bloating on its own does not confirm diverticulitis, since conditions such as IBS or small intestinal bacterial overgrowth (SIBO) can look similar. A GP can help rule these in or out. For a closer look at bowel changes specifically, see what diverticulitis stool can look like.
When Do Diverticulitis Symptoms Need Emergency Care?
Most flares can be managed with antibiotics, rest and a lighter diet at home. A smaller number of flares involve a complication, such as an abscess or a perforation, and these need urgent hospital treatment (Mayo Clinic).
Symptom | What It Can Mean | What To Do |
Severe pain that does not ease | Possible abscess or worsening inflammation | Contact your GP urgently or attend A&E |
Fever above 38°C with pain | Infection spreading beyond the diverticula | Seek same-day medical advice |
Heavy or persistent rectal bleeding | Diverticular haemorrhage | Call 999 or go to A&E |
Unable to keep fluids down | Risk of dehydration or bowel obstruction | Seek same-day medical advice |
Rigid, very tender abdomen with pain | Possible perforation and peritonitis | Call 999 immediately |
“I ended up with sepsis after waiting too long, my bowel also perforated after trying to manage the pain at home. If pain is severe and does not settle, going in sooner rather than later is safer.”
– Pauline, Bristol
How Do Members Manage Flare Up Symptoms?
Members most often describe a short period of clear fluids followed by soft, low-fibre foods while a flare settles, alongside any antibiotics prescribed by their GP.
“A clear liquid diet for a few days, then soft foods like eggs, mashed potato, rice and well-cooked vegetables, gave my gut the rest it needed before I reintroduced fibre slowly.”
– Janet, Edinburgh
“I was told never to take ibuprofen during a flare, only paracetamol, because it can raise the risk of bleeding.”
– Carol, Liverpool
This lines up with Mayo Clinic’s note that NSAIDs such as ibuprofen are among the factors linked to a higher risk of diverticulitis and its complications. For more on medication choices, see our guide to the best medication for diverticulitis.
Frequently Asked Questions
Does Diverticulitis Always Cause A Fever?
No. Fever is a common sign of infection during a flare up, but some members manage flares without ever running a temperature, relying instead on pain as their main warning sign.
“I measure my pain out of ten, and anything over a six sends me straight to A&E.”
– Margaret, Nottingham
Anyone with new or worsening abdominal pain should get it checked, fever or not.
Can Diverticulitis Cause Bloating Without Pain?
Yes. Some members describe daily bloating with very little pain, particularly between flares. Persistent bloating alone does not confirm diverticulitis, so it is worth raising with a GP.
How Long Does A Diverticulitis Flare Up Last?
Mild flares often settle within a few days on antibiotics and a lighter diet, while flares involving an abscess or perforation can mean a hospital stay of a week or longer, plus a longer recovery. For a fuller breakdown, see how long a diverticulitis flare up can last.
Is It Safe To Take Ibuprofen During A Flare Up?
Members are frequently advised to avoid ibuprofen and other NSAIDs during a flare and to use paracetamol instead, since NSAIDs are associated with a higher risk of bleeding and complications. Always confirm pain relief choices with a GP or pharmacist.
Key Takeaways
- The core signs of a flare up are lower left abdominal pain, fever, nausea and a change in bowel habit.
- Diverticulosis (the pockets) and diverticulitis (the inflamed pockets) are not the same thing, and only the second causes classic flare up symptoms.
- Bloating can persist between flares even once pain has settled.
- Severe, unrelenting pain, heavy bleeding, or being unable to keep fluids down are reasons to seek urgent medical care.
- Tracking food and symptoms daily helps identify personal triggers and gives a doctor something concrete to work from.
More Reading
Stop Guessing. Start Understanding.
All of these symptoms can leave someone feeling overwhelmed, especially when they seem to come out of nowhere. Seeking medical attention quickly helps with both the physical symptoms and the stress that comes with living with this condition. Members who keep a food and symptoms diary often find it easier to spot their own triggers and to have a useful record ready for their GP.
This article is not medical advice. Medical advice should always be sought from a qualified medical practitioner.
