Lifestyle

6 Signs of Diverticulitis Most People Mistake for an Upset Stomach

By Mike Harper · October 18, 2026

You may never have heard of diverticulosis. If you’re over 50, there’s a fair chance you have it anyway. The National Institute of Diabetes and Digestive and Kidney Diseases says more than 30% of U.S. adults ages 50 to 59 and more than 70% of those older than 80 have diverticulosis, small pouches that push outward through weak spots in the wall of the colon.

Most of the time those pouches cause no trouble. When one becomes inflamed, it’s called diverticulitis, and it can come on suddenly. Fewer than 5% of people with diverticulosis develop it, NIDDK says, but about 200,000 people in the U.S. are hospitalized for diverticulitis every year.

The early signs are easy to blame on something you ate. These six are worth a call to your doctor.

Pain low on the left side. NIDDK says diverticulitis pain shows up most often in the lower left side of your abdomen. That’s where the sigmoid colon sits, and it’s where most pouches form. Cleveland Clinic notes that people of Asian descent more often get pouches on the right side, so pain there doesn’t rule it out.

Pain that builds over several days. Diverticulitis pain is typically severe and sudden, according to NIDDK, but it can also start mild and worsen over several days, and its intensity can shift. A belly ache that’s still getting worse on day three is not one to wait out.

Fever or chills along with the pain. NIDDK lists fevers and chills among the acute symptoms. A fever on top of belly pain is a reason to call your doctor rather than ride it out on the couch.

Constipation, or sometimes diarrhea. NIDDK names both. Cleveland Clinic says constipation is more common during an attack, with diarrhea showing up less often. A sudden change in your usual pattern, paired with that lower belly pain, is worth mentioning.

Nausea or vomiting. This is the symptom that sends people looking for something to settle their stomach. With localized pain in the lower abdomen, it’s part of the diverticulitis picture NIDDK describes.

A swollen belly that hurts to touch. Cleveland Clinic lists a distended abdomen among the symptoms. A belly that turns rigid and very sensitive to touch is one of its signs of complicated diverticulitis, along with fresh blood in your stool, a pale face or weakness, and needing to pee often or irritation when you do. Those need care right away.

Mild, uncomplicated diverticulitis can sometimes clear up on its own, Cleveland Clinic says, but it should still be checked, often with a CT scan, because the symptoms look like many other conditions. For pain relief at home, the clinic suggests acetaminophen, since NSAIDs such as aspirin, ibuprofen, and naproxen can raise the risk of bleeding. NIDDK separately lists NSAIDs and steroids among factors that may raise the risk of diverticulitis or its complications. Smoking, obesity, lack of activity, and a diet low in fiber and high in red meat are on that list too.

Fiber is the long-term habit worth building. NIDDK points to the Dietary Guidelines target of 14 grams of fiber per 1,000 calories, or 28 grams a day on a 2,000-calorie diet, and suggests adding it a little at a time. A cup of raspberries has 8 grams. Half a cup of cooked lentils has 7.8. As for the old advice to skip nuts, popcorn, and seeds, NIDDK says more recent research suggests those foods are not harmful to people with diverticulosis.

This article is for general information and is not medical advice. Severe abdominal pain, fever, or blood in your stool needs prompt medical attention.