Disclaimer: This article does not constitute medical advice. Always seek advice from a qualified medical practitioner about your own symptoms, diagnosis and treatment.
- What Are The First Signs Of A Diverticulitis Flare Up?
- What Does A Diverticulitis Flare Up Feel Like?
- What Do Medical Sources List As Flare Up Symptoms?
- How Do Diverticulosis, Diverticular Disease And Diverticulitis Symptoms Differ?
- Why Do Diverticulitis Symptoms Look Like IBS?
- Can Diverticulitis Cause Blood In The Stool?
- Does Diverticulitis Cause Back, Hip Or Thigh Pain?
- Why Do Diverticulitis Symptoms Continue Between Flares?
- Why Do Doctors Sometimes Miss Or Downplay Diverticulitis Symptoms?
- Which Tests Help Confirm A Diverticulitis Flare Up?
- Which Diverticulitis Symptoms Need Urgent Medical Help?
- What Should You Note Down Before You See A Doctor?
- Frequently Asked Questions
- Does Diverticulitis Always Cause A Fever?
- Can Diverticulitis Cause Symptoms On The Right Side?
- Does Diverticulitis Cause Weight Loss?
- Do Antibiotics Settle Diverticulitis Symptoms Straight Away?
- How Long Do Diverticulitis Flare Up Symptoms Last?
- Key Takeaways
- Sources
- Stop Guessing. Start Understanding
This article is based on anonymised discussions from our Diverticulitis Club group on Facebook. We changed all names and locations.
A diverticulitis flare up causes pain, most often in the lower left abdomen, together with abdominal tenderness, fever, nausea and a change in bowel habit such as sudden diarrhoea or constipation. Mayo Clinic describes the pain as usually sudden and intense, although it can start mild and build over a day or two. The NHS advises you to contact a GP as soon as possible if you have these symptoms. Our members add detail that medical summaries often leave out: pain that spreads to the back, hip and thigh, bleeding with bowel movements, and symptoms that carry on between flares. Bowel cancer, inflammatory bowel disease and irritable bowel syndrome (IBS) share many of these symptoms, so only a doctor can confirm the cause.
What Are The First Signs Of A Diverticulitis Flare Up?
The first sign of a diverticulitis flare up is usually lower left abdominal pain that does not ease. NHS inform states that diverticulitis pain is constant and severe rather than stop-start, and that it develops over a day or two. Mayo Clinic adds that nausea, fever, tenderness when you touch the abdomen and a sudden change in stools often come with the pain. BMJ Best Practice lists left lower abdominal pain, fever and a raised white blood cell count as the key findings doctors look for, and it names bloating and constipation as further signs.
Early Sign | What Medical Sources Report | What Members Describe |
Lower left abdominal pain | Mayo Clinic: usually sudden and intense, sometimes mild at first. NICE: most people feel pain on the left side, where diverticula most often form. | Constant, raw pain that is worse before a bowel movement. |
Fever | Mayo Clinic and BMJ Best Practice both list fever. | One member reported a low grade fever alongside constant pain. |
Change in bowel habit | Mayo Clinic: sudden diarrhoea or constipation. NICE: constipation, diarrhoea or both. | One member went from constipation with blood to diarrhoea with blood. |
Bloating and cramping | BMJ Best Practice lists bloating. The NICE panel removed bloating from its statements and called it non-specific. | Members describe painful bloating and cramping after meals. |
Abdominal tenderness | Mayo Clinic and BMJ Best Practice list tenderness. BMJ also lists guarding in the lower left abdomen. | Two members describe pain that spreads beyond the abdomen. |
Blood with bowel movements | NICE: occasional rectal bleeds. Pharmaceutical Journal: some diverticula bleed. | One member reported blood with every bowel movement. |
What Does A Diverticulitis Flare Up Feel Like?
A diverticulitis flare up feels like constant, localised abdominal pain that bowel movements make worse. One member listed her symptoms in a single post, and her account shows how many symptoms arrive at once.
“Constant raw abdominal pain. I was sore from my belly to mid-thigh, my lower back and my bottom. I was constipated with blood, and now it is diarrhoea with blood. When I need the toilet I have horrific pain, and I am rolling around moaning before I rush there. I also have a low grade fever.”
Rachel, Perth
Another member described a pattern linked to meals, which she had before surgery to remove her sigmoid colon (the curved final section of the colon where most diverticula form).
“Before I had my sigmoid colon removed I had daily pelvic pain after meals. I had frequent painful bloating and cramping after eating certain foods, and sometimes just because.”
Joan, Auckland
Members who link symptoms to particular foods can read more in our guide on whether food triggers diverticulitis.
What Do Medical Sources List As Flare Up Symptoms?
Medical sources agree that diverticulitis causes pain, fever and bowel changes, and they disagree on bloating. The table compares what each source states.
Source | Symptoms Listed | Notes |
Mayo Clinic | Pain, most often lower left, usually sudden and intense. Nausea, fever, abdominal tenderness, and sudden diarrhoea or constipation. | About 15% of people with diverticulitis develop complications. |
NHS inform | Constant, severe pain that develops over a day or two. | Intermittent pain points to diverticular disease instead. |
NICE evidence review (NG147) | Left-sided pain, left lower abdominal tenderness, constipation, diarrhoea or both, and occasional rectal bleeding. | Bloating and mucus from the rectum were removed as non-specific. |
BMJ Best Practice | Left lower abdominal pain, fever and a raised white cell count. Also guarding, tenderness, bloating and constipation. | Evidence last reviewed 20 September 2026. |
Pharmaceutical Journal | Severe lower abdominal pain and tenderness, fever and general malaise. Blood in the stool if a diverticulum bleeds. | Written for pharmacists who first meet many patients. |
The NICE evidence review explains why a symptom list alone cannot settle a diagnosis. Its authors state that doctors usually do not diagnose diverticular disease from symptoms alone and that further assessment and investigations confirm it.
How Do Diverticulosis, Diverticular Disease And Diverticulitis Symptoms Differ?
Diverticulosis usually causes no symptoms, diverticular disease causes intermittent pain, and diverticulitis causes constant, severe pain with signs of inflammation or infection. The Pharmaceutical Journal adds that diverticular disease is a chronic condition with symptoms that remit and relapse. Our guide on the difference between diverticulitis and diverticulosis covers the terms in more depth.
Stage | What It Means | Typical Symptoms | Pain Pattern |
Diverticulosis | Pouches (diverticula) are present in the colon wall. | Usually none. | None |
Diverticular disease | The pouches cause symptoms, without infection. | Lower abdominal pain, usually lower left. Constipation, diarrhoea or both. Bloating. | Stop-start |
Diverticulitis | One or more pouches become inflamed or infected. | Severe pain, fever, nausea, tenderness and stool changes. | Constant |
Members use these terms differently from doctors. One member asked the group a question that shows the gap.
“Is it normal when we are in diverticulosis (not a flare) to still get symptoms and sensitivity?”
Lorna, Aberdeen
Doctors reserve diverticulosis for pouches without symptoms. Members often use the word for the stage between flares, even when they have symptoms every week. That difference in language explains some of the confusion in appointments.
Why Do Diverticulitis Symptoms Look Like IBS?
Diverticulitis symptoms look like IBS because both conditions cause abdominal pain, bloating and bowel changes. The NHS states that the symptoms of diverticular disease and diverticulitis are similar to those of IBS. The NICE evidence review lists IBS, inflammatory bowel disease, colorectal cancer and, in women, ovarian or other gynaecological conditions among the possible alternative explanations when symptoms first appear.
One member spent several years being told her symptoms were IBS before a scan showed otherwise.
“I had been telling my doctor about these symptoms for several years. She told me it was most likely IBS caused by stress. A month ago I saw a new doctor. He ordered a CT scan, which showed acute diverticulitis in my sigmoid colon, and he prescribed two antibiotics. That was it, no other instructions. Is it just me, or does there not seem to be very good medical care for this condition?”
Barbara, Hamilton
Other members recognised the pattern straight away.
“I was always told it was IBS. The doctor mentioned his surprise at the many pockets while I was waking up from the scope, then left. No follow up appointment, no advice, no explanation.”
Doreen, Hobart
“I have discomfort every day. I am not sure if it is the diverticulitis or the IBS. My GP did not seem to know either.”
Eileen, Cork
Another member raised stress as the label doctors reach for first.
“I don’t know if men get as many health issues attributed to stress, but stress seems to be the go-to answer for a lot of women’s problems.”
Gwen, Calgary
Members who live with IBS describe a heavy daily load.
“I have had so many accidents. I’ve stopped dating. Once the urge hits, I have a matter of minutes to find a bathroom.”
Maureen, Winnipeg
The NICE review looked for symptoms that separate the conditions and found little. It included one study, a 2015 case-control study of 1,629 Japanese adults who were having colonoscopies. The study compared people with diverticulosis (pouches only) with people without it. Each odds ratio in the table below compares the two groups, where 1.0 means no difference between them.
Symptom | Adjusted Odds Ratio (95% Range) | What The Study Shows |
Abdominal discomfort | 1.03 (0.93 to 1.14) | No clear difference |
Constipation | 0.85 (0.78 to 0.93) | Slightly less common with pouches |
Diarrhoea | 1.02 (0.93 to 1.12) | No clear difference |
Loose stool | 1.03 (0.93 to 1.14) | No clear difference |
Hard stool | 0.89 (0.78 to 1.02) | No clear difference |
NICE rated this evidence very low quality. The study came from one country, and it excluded people with a history of acute diverticulitis, so it describes pouches and not flare ups. The NICE committee noted that Japanese and UK diets differ, and it concluded that the evidence was too thin to recommend which symptoms point to diverticular disease. The finding still carries a practical message: pouches alone do not reliably cause everyday gut symptoms, so other explanations, including IBS, deserve a proper look.
NICE also pooled two studies of 1,862 people and found that people with IBS were about 1.8 times as likely to have diverticular disease (95% range 1.3 to 2.49). It graded that evidence low quality. A member can therefore have both conditions at once.
Can Diverticulitis Cause Blood In The Stool?
Diverticulitis can cause blood in the stool, and any rectal bleeding needs a medical assessment. NICE states that rectal bleeding can occur if a blood vessel in a diverticulum erodes, and the Pharmaceutical Journal states that some diverticula bleed. NICE also warns that rectal bleeding looks similar to bowel cancer and inflammatory bowel disease, which is why a doctor must investigate it. NHS inform states that diverticular disease does not cause weight loss, so blood in the stool together with weight loss needs a GP visit.
Members disagree on how to read the amount of blood they see. One member described bleeding with every bowel movement and compared it with the images she found online.
“It’s every time I go, but it’s not staining the whole toilet water red like some pictures I see on Google.”
Rachel, Perth
Another member replied with a reminder that blood has more than one source.
“Blood in a stool doesn’t automatically mean a bleed. It can be haemorrhoids. But it needs checking.”
Marilyn, Dunedin
Rachel replied that the emergency department had already checked for haemorrhoids during its examination. Our guide to what diverticulitis stool can look like covers colour, consistency and urgency in more detail.
Does Diverticulitis Cause Back, Hip Or Thigh Pain?
None of the five medical sources reviewed for this article lists back, hip or thigh pain as a core symptom of diverticulitis. NICE describes pain on the left side of the abdomen, and Mayo Clinic describes pain in the abdomen, most often lower left. Two members report pain that travels further.
“I also have pain in my back and hip.”
Barbara, Hamilton
The member quoted earlier in this article, who described soreness from her belly to mid-thigh and lower back, reported the same spread. NICE lists gynaecological conditions, and the Pharmaceutical Journal lists gynaecological and urological conditions, among the alternative explanations for lower abdominal pain, so pain that spreads is worth describing carefully to your GP. Our guide on how to know if pain is diverticulitis explores that question.
Why Do Diverticulitis Symptoms Continue Between Flares?
Diverticulitis symptoms continue between flares for many members, and no single medical explanation covers everyone. More than two dozen members replied to the question about symptoms outside a flare, and almost all of them said they have symptoms too. This is an informal count from one Facebook thread and not a study, but the replies share a clear pattern.
Member | What They Said |
Fran, Cardiff | “I haven’t had a flare in over a year and still have weekly issues.” |
Moira, Galway | “I never thought when I was diagnosed that it would be this constant, this bad.” |
Colleen, Leicester | “Yes, daily. Sometimes I stay in bed with a heating pad.” |
Heather, Sacramento | “Yes, 15 years later.” |
Roy, Tulsa | “Four months and still issues.” |
Trevor, Dundee | “Never without them anymore.” |
Norma, Bath | “Permanently now.” |
The replies also show the emotional cost of symptoms that other people cannot see.
“Yes, always. Very annoying and frustrating. After seven years my family still does not understand.”
Ruth, Portland
Ruth added that her family sometimes tell her to wear a nappy if she goes anywhere. Another member replied that the remark was unkind and hurtful.
Medical sources give three overlapping explanations for continuing symptoms. First, the Pharmaceutical Journal describes diverticular disease as a chronic condition with relapsing symptoms. Second, it notes that chronic symptoms such as abdominal pain, bloating and altered bowel habit overlap with IBS and make diagnosis difficult. Third, a 2019 review by Strate and Morris reports that about 40% of people with scan-confirmed diverticulitis in one trial still had mild to moderate pain or bowel changes a year later. A doctor can work out which explanation applies to you. One member described still feeling unwell well after treatment ended.
“Eight weeks after finishing 10 days of antibiotics, I’m just miserable. Still only eating mashed plain food.”
Dawn, Exeter
Members also report that symptoms flare when something irritates the bowel. One member described the link in her own words.
“I think with mine I get pains when I do anything to irritate what is already scarred. I know if I have eaten something wrong or am stressed. I will get pain.”
Valerie, Adelaide
Our guides on what triggers diverticulitis flare ups and whether stress triggers diverticulitis symptoms cover those patterns.
Why Do Doctors Sometimes Miss Or Downplay Diverticulitis Symptoms?
Doctors sometimes miss or downplay diverticulitis because its symptoms overlap with other conditions and because the diagnosis depends on tests, not on symptoms alone. The NICE evidence review states that the diagnosis often comes through investigations for other bowel conditions with overlapping symptoms. BMJ Best Practice names CT as the imaging test of choice for acute diverticulitis.
The same member who listed her symptoms above went to an emergency department, had a CT scan and an examination, and went home with a different label from the one she expected.
“They sent me home with a possible very mild colitis. I do not think I have very mild colitis. A couple of nurse friends and the second doctor I saw think it is diverticulitis. I got antibiotics on Friday, but my symptoms have been exactly the same since Tuesday.”
Rachel, Perth
She also asked several clinicians and a health helpline whether she should follow a specific diet, and she reported that they all told her she could eat what she liked. That answer differs from the advice other members receive, and the medical evidence explains why. The Pharmaceutical Journal quotes the NICE clinical knowledge summary, which states that its fibre recommendation rests on limited and conflicting evidence. Members who hear different answers from different clinicians are reflecting a real gap in the evidence.
Other members describe feeling brushed off after a diagnosis.
“I’ve had diverticulitis three times in 11 months. The last time the doctor gave me antibiotics and just told me to research it. It’s like nobody takes it seriously!”
Janet, Stirling
“I have to battle to get antibiotics. This disease doesn’t seem to be recognised by anyone in the medical profession, even though my GP referred me for a colonoscopy and the hospital confirmed diverticulitis.”
Stella, Nottingham
Our guide on what can be mistaken for diverticulitis explains which other conditions doctors consider.
Which Tests Help Confirm A Diverticulitis Flare Up?
Doctors confirm a diverticulitis flare up with blood tests and, in many cases, imaging. The table shows the tests that the medical sources name.
Test | What It Checks | Source |
Full blood count and C-reactive protein | Signs of inflammation or infection, including a raised white cell count | BMJ Best Practice; Pharmaceutical Journal |
Urea and electrolytes | Hydration and kidney function | BMJ Best Practice |
Faecal calprotectin | Inflammation in the intestine | Pharmaceutical Journal |
CT scan of the abdomen | Inflamed pouches and complications such as an abscess | BMJ Best Practice |
Ultrasound or MRI | Alternative imaging when CT does not suit | BMJ Best Practice |
Colonoscopy | Pouches in the colon wall, and other conditions | Pharmaceutical Journal |
Your doctor decides which tests suit your symptoms.
Which Diverticulitis Symptoms Need Urgent Medical Help?
Constant, unexplained abdominal pain needs medical care, particularly when you also have a fever and notable changes in your stools. Mayo Clinic gives that advice, and it states that about 15% of people with diverticulitis develop complications. Those complications include an abscess (a pocket of pus), a blockage of the colon, a fistula (an abnormal passage between the bowel and another organ), peritonitis after a tear in the colon wall, and bleeding. Our guide on when to go to the ER with diverticulitis goes into more detail.
Symptom | What It Can Signal | What To Do |
Constant, unexplained abdominal pain with fever or stool changes | Diverticulitis or another condition that needs a diagnosis | Contact your GP as soon as possible |
Severe pain that keeps worsening or does not settle | A complication such as an abscess | Seek urgent medical review the same day |
Heavy or ongoing rectal bleeding | Diverticular bleeding or another bowel condition | Seek emergency care |
Unable to keep fluids down, or a rigid, very tender abdomen | A blockage or peritonitis | Seek emergency care |
What Should You Note Down Before You See A Doctor?
A short written record helps a doctor separate diverticulitis from IBS and other conditions. A useful record covers:
- When the pain started, where it sits, and whether it is constant or stop-start.
- Any temperature readings, nausea or vomiting.
- Bowel changes by date, including diarrhoea, constipation and any blood.
- Every medicine you take. Mayo Clinic lists steroids, opioids and NSAIDs such as ibuprofen and naproxen among the factors that raise the risk of diverticulitis, and BMJ Best Practice lists age over 50 and obesity among the risk factors.
Our Food And Symptoms Diary records all of this in one place and lets you share a clear history with your GP.
Frequently Asked Questions
Does Diverticulitis Always Cause A Fever?
No source reviewed for this article states that fever occurs in every flare. Mayo Clinic and BMJ Best Practice list fever as a common sign of diverticulitis. One member reported only a low grade fever alongside constant pain, and she still needed medical assessment. Anyone with new or worsening abdominal pain should get it checked, with or without a fever.
Can Diverticulitis Cause Symptoms On The Right Side?
Yes. NICE states that people of Asian origin may experience right-sided symptoms, and the Pharmaceutical Journal states that right-sided disease is more common in Asian populations, while Western populations mostly develop disease in the sigmoid colon on the left.
Does Diverticulitis Cause Weight Loss?
NHS inform states that diverticular disease does not cause weight loss, and it advises you to see your GP if you are losing weight, seeing blood in your stools or having frequent bowel changes. The Pharmaceutical Journal also lists unplanned weight loss among the questions pharmacists ask when they suspect the condition.
Do Antibiotics Settle Diverticulitis Symptoms Straight Away?
Not always, and members report mixed experiences. The Pharmaceutical Journal describes a randomised trial in which antibiotics for acute uncomplicated diverticulitis neither sped recovery nor prevented complications or recurrence, and it recommends reserving them for complicated cases. Your doctor decides what suits you. Members describe both sides.
“I was given antibiotics again. They make you feel twice as bad too.”
Eileen, Cork
“I think the antibiotics have so helped me. I’m afraid to come off them.”
Hazel, Bolton
Our guide to medication for diverticulitis covers what members report about treatment.
How Long Do Diverticulitis Flare Up Symptoms Last?
Duration varies widely between members. Some report symptoms for weeks after antibiotics finish, as Dawn did above. Our guide on how long a diverticulitis flare up lasts explains what members report.
Key Takeaways
- Diverticulitis flare up symptoms are lower left abdominal pain, tenderness, fever, nausea and a change in bowel habit.
- Diverticulosis usually causes no symptoms, diverticular disease causes stop-start pain, and diverticulitis causes constant, severe pain.
- IBS, inflammatory bowel disease and bowel cancer share many of these symptoms, so a diagnosis needs tests.
- The NICE evidence review found that common gut symptoms did not reliably predict pouches in one low-quality study.
- Members report back, hip and thigh pain, bleeding and symptoms between flares, and no medical source reviewed here lists back, hip or thigh pain as a core symptom.
- Constant, unexplained pain with fever or stool changes needs medical care, and heavy bleeding needs emergency care.
- Members often hear different explanations from different clinicians, so bring your own questions and notes to your own doctor.
Sources
- Diverticular disease and diverticulitis.
- NHS inform. Diverticular disease and diverticulitis.
- Mayo Clinic Staff. Diverticulitis: symptoms and causes.
- National Institute for Health and Care Excellence. Diverticular disease: diagnosis and management, evidence review B: symptoms and signs of diverticular disease (NG147).
- BMJ Best Practice. Diverticular disease. Evidence last reviewed 20 September 2026.
- Copeland E, St Clair Jones A. Diverticular disease and diverticulitis: causes, symptoms and treatment. The Pharmaceutical Journal, 2019.
- Strate LL, Morris AM. Epidemiology, pathophysiology, and treatment of diverticulitis. Gastroenterology, 2019.
If you live with these symptoms and want to spot your own patterns, you can start the Food And Symptoms Diary today. You can also join the conversation in our forums and our Facebook group. Reading what other members experience will not give you a diagnosis, but it shows you that you are not alone.
Disclaimer: This article does not constitute medical advice. Diverticulitis affects everyone differently. Always seek advice from a qualified medical practitioner about your own symptoms, diagnosis and treatment.
