Diverticulitis Symptoms and Diet: What to Know During a Flare

What does a diverticulitis flare actually feel like?

The most recognizable symptom is a persistent aching or cramping pain in the lower-left abdomen. The pain usually builds over hours to a day and is often described as steady rather than colicky — it tends to stay rather than come and go. Other common symptoms include low-grade fever, nausea, bloating, and a change in bowel habits (either constipation or, less often, looser stools). Some people notice tenderness if they press on the lower abdomen 1Ref 1Qaseem A, Etxeandia-Ikobaltzeta I, Lin JS, Fitterman N, Shamliyan T, Wilt TJ (2022).Diagnosis and Management of Acute Left-Sided Colonic Diverticulitis: A Clinical Guideline From the American College of Physicians.Diagnosis, dietary management, antibiotic use, CT imaging, and dietary fiber recommendations for diverticulitis; revision of nuts/seeds restriction; selective antibiotic use in uncomplicated cases.

In some people — particularly those with a longer colon or in some Asian populations — the pain may be on the right side rather than the left. If you have had diverticulosis confirmed on imaging or colonoscopy and develop this pattern, diverticulitis is a reasonable concern to bring to a clinician promptly 1Ref 1Qaseem A, Etxeandia-Ikobaltzeta I, Lin JS, Fitterman N, Shamliyan T, Wilt TJ (2022).Diagnosis and Management of Acute Left-Sided Colonic Diverticulitis: A Clinical Guideline From the American College of Physicians.Diagnosis, dietary management, antibiotic use, CT imaging, and dietary fiber recommendations for diverticulitis; revision of nuts/seeds restriction; selective antibiotic use in uncomplicated cases2Ref 2Shaukat A, Kahi CJ, Burke CA, Rabeneck L, Sauer BG, Rex DK (2021).ACG Clinical Guidelines: Colorectal Cancer Screening 2021.Colonoscopy timing after diverticulitis episode to rule out colorectal cancer; colorectal screening framework.

How is diverticulitis different from diverticulosis?

Diverticulosis simply means the pouches (diverticula) are present — which is common as people age. Most people with diverticulosis have no symptoms and never develop a problem. Diverticulitis is when one or more of those pouches become inflamed or infected.

Most people with diverticulosis never develop diverticulitis; those who do usually have isolated episodes, though some experience recurrent flares. A low-fiber, high-processed-food diet over time is associated with greater diverticulosis risk 1Ref 1Qaseem A, Etxeandia-Ikobaltzeta I, Lin JS, Fitterman N, Shamliyan T, Wilt TJ (2022).Diagnosis and Management of Acute Left-Sided Colonic Diverticulitis: A Clinical Guideline From the American College of Physicians.Diagnosis, dietary management, antibiotic use, CT imaging, and dietary fiber recommendations for diverticulitis; revision of nuts/seeds restriction; selective antibiotic use in uncomplicated cases. The older advice to permanently avoid nuts and seeds has been largely revised — evidence does not reliably support that restriction 1Ref 1Qaseem A, Etxeandia-Ikobaltzeta I, Lin JS, Fitterman N, Shamliyan T, Wilt TJ (2022).Diagnosis and Management of Acute Left-Sided Colonic Diverticulitis: A Clinical Guideline From the American College of Physicians.Diagnosis, dietary management, antibiotic use, CT imaging, and dietary fiber recommendations for diverticulitis; revision of nuts/seeds restriction; selective antibiotic use in uncomplicated cases.

What should I eat during a flare?

When a flare is active, the goal is to let the colon rest. A standard progression recommended in guidelines 1Ref 1Qaseem A, Etxeandia-Ikobaltzeta I, Lin JS, Fitterman N, Shamliyan T, Wilt TJ (2022).Diagnosis and Management of Acute Left-Sided Colonic Diverticulitis: A Clinical Guideline From the American College of Physicians.Diagnosis, dietary management, antibiotic use, CT imaging, and dietary fiber recommendations for diverticulitis; revision of nuts/seeds restriction; selective antibiotic use in uncomplicated cases2Ref 2Shaukat A, Kahi CJ, Burke CA, Rabeneck L, Sauer BG, Rex DK (2021).ACG Clinical Guidelines: Colorectal Cancer Screening 2021.Colonoscopy timing after diverticulitis episode to rule out colorectal cancer; colorectal screening framework:

1. Clear liquids first — water, broth, clear juices, plain gelatin, popsicles — until pain begins to ease (usually a few days). 2. Low-fiber soft foods as symptoms improve — white rice, plain crackers, eggs, well-cooked vegetables without skins or seeds, banana, applesauce. 3. Gradual return to normal diet over one to two weeks after symptoms fully resolve.

High-fiber foods (raw vegetables, whole grains, beans, nuts) come back only after full recovery. Large meals should be avoided during a flare. Your clinician will guide the right timeline for your situation — this is a general framework, not a prescription.

What does a fiber-rich diet between flares actually do?

Once you have recovered from a flare, a high-fiber diet is generally recommended to reduce the risk of future episodes 1Ref 1Qaseem A, Etxeandia-Ikobaltzeta I, Lin JS, Fitterman N, Shamliyan T, Wilt TJ (2022).Diagnosis and Management of Acute Left-Sided Colonic Diverticulitis: A Clinical Guideline From the American College of Physicians.Diagnosis, dietary management, antibiotic use, CT imaging, and dietary fiber recommendations for diverticulitis; revision of nuts/seeds restriction; selective antibiotic use in uncomplicated cases. This means vegetables, fruit, legumes, and whole grains, along with adequate fluid intake. Staying physically active and maintaining a healthy weight are also associated with lower risk. Some evidence suggests limiting red and processed meat may be beneficial, though the relationship is not perfectly established 1Ref 1Qaseem A, Etxeandia-Ikobaltzeta I, Lin JS, Fitterman N, Shamliyan T, Wilt TJ (2022).Diagnosis and Management of Acute Left-Sided Colonic Diverticulitis: A Clinical Guideline From the American College of Physicians.Diagnosis, dietary management, antibiotic use, CT imaging, and dietary fiber recommendations for diverticulitis; revision of nuts/seeds restriction; selective antibiotic use in uncomplicated cases.

A registered dietitian can help build a practical eating plan that achieves adequate fiber intake without inadvertently triggering a flare during the transition period.

Do I need antibiotics, and can I be treated at home?

This is an area where guidelines have evolved. The American College of Physicians guideline from 2022 notes that for uncomplicated, mild acute diverticulitis, selective (rather than routine) antibiotic use is now supported — some patients recover without them 2Ref 2Shaukat A, Kahi CJ, Burke CA, Rabeneck L, Sauer BG, Rex DK (2021).ACG Clinical Guidelines: Colorectal Cancer Screening 2021.Colonoscopy timing after diverticulitis episode to rule out colorectal cancer; colorectal screening framework. However, your clinician needs to assess your specific situation: severity, fever, lab values, and risk factors (including immunosuppression, which significantly changes the picture).

Moderate to severe cases — those with high fever, significant pain, inability to tolerate fluids, complications such as abscess, or immunocompromised status — typically require antibiotics and may need hospitalization. Do not self-treat a suspected diverticulitis flare without a clinical evaluation, because complications can develop quickly 1Ref 1Qaseem A, Etxeandia-Ikobaltzeta I, Lin JS, Fitterman N, Shamliyan T, Wilt TJ (2022).Diagnosis and Management of Acute Left-Sided Colonic Diverticulitis: A Clinical Guideline From the American College of Physicians.Diagnosis, dietary management, antibiotic use, CT imaging, and dietary fiber recommendations for diverticulitis; revision of nuts/seeds restriction; selective antibiotic use in uncomplicated cases2Ref 2Shaukat A, Kahi CJ, Burke CA, Rabeneck L, Sauer BG, Rex DK (2021).ACG Clinical Guidelines: Colorectal Cancer Screening 2021.Colonoscopy timing after diverticulitis episode to rule out colorectal cancer; colorectal screening framework.

A CT scan of the abdomen and pelvis (usually with contrast) is the most reliable test for confirming diverticulitis and checking for complications like abscess or perforation 2Ref 2Shaukat A, Kahi CJ, Burke CA, Rabeneck L, Sauer BG, Rex DK (2021).ACG Clinical Guidelines: Colorectal Cancer Screening 2021.Colonoscopy timing after diverticulitis episode to rule out colorectal cancer; colorectal screening framework.

When should I have a colonoscopy after a diverticulitis episode?

After recovering from a first episode, a colonoscopy is generally recommended four to six weeks later to rule out colon cancer or another condition that could have triggered the presentation 3Ref 3National Institute of Diabetes and Digestive and Kidney Diseases (2023).Colonoscopy.Colonoscopy as a follow-up procedure after diverticulitis for colorectal evaluation. It is not done during the acute episode when the bowel is inflamed. Colonoscopy timing follows standard colorectal cancer screening guidance 3Ref 3National Institute of Diabetes and Digestive and Kidney Diseases (2023).Colonoscopy.Colonoscopy as a follow-up procedure after diverticulitis for colorectal evaluation; anyone at screening age who has not had a recent colonoscopy should discuss the schedule with their clinician.