Diverticulitis Symptoms: How to Recognize Them and When It's an Emergency

A sharp, steady ache settles into the lower left side of your belly, you feel a little feverish, and your stomach is tender to the touch. If you're searching for what's going on, you may be wondering whether this is diverticulitis. It's a common and treatable condition, but some symptoms do need prompt medical attention, so it helps to know what to watch for.

Here's a plain-language guide to the symptoms of diverticulitis: what they feel like, how fast they come on, and the warning signs that mean you should call your doctor or head to the emergency room.

What is diverticulitis?

Many people develop small pouches that bulge outward through weak spots in the wall of the colon (the large intestine). Having these pouches is called diverticulosis, and it's extremely common with age. Diverticulitis is what happens when one or more of those pouches becomes inflamed or infected.

The two terms sound alike but mean different things. Diverticulosis on its own usually causes no symptoms at all. Diverticulitis is the painful, inflamed version, and it's far less common. According to the NIH, fewer than 5% of people with diverticulosis ever go on to develop diverticulitis.

What are the symptoms of diverticulitis?

The hallmark symptom is pain in the lower left side of the abdomen. It's usually significant, persistent, and severe enough that many people seek care for it. In fact, left lower quadrant pain is the most common presenting symptom, occurring in about 70% of patients.

Pain rarely travels alone. Diverticulitis often brings a cluster of other digestive and whole-body symptoms.

• Persistent pain, most often in the lower left abdomen
• Fever and chills
• Nausea and vomiting
• Tenderness when the belly is pressed
• A change in bowel habits, usually constipation but sometimes diarrhea
• Bloating and gas

How quickly do diverticulitis symptoms come on?

Diverticulitis tends to announce itself fairly suddenly. According to the Mayo Clinic, symptoms usually develop quickly, often within several hours. That's different from the slow, vague discomfort some people expect from a digestive problem.

So if you go from feeling fine to having steady, worsening left-sided belly pain plus a fever over the course of a day, that pattern fits diverticulitis. A rapid onset of severe pain is one of the reasons people end up in urgent care or the emergency room.

Diverticulitis vs. diverticulosis: what's the difference?

This distinction matters because it changes what you should do next. Diverticulosis is simply the presence of the pouches. It's common, becomes more likely as you age, and most people who have it never know it because it causes no symptoms.

Diverticulitis is the complication: inflammation or infection of those pouches, with real symptoms like pain and fever. The risk of crossing from one to the other over a lifetime is low. StatPearls estimates that only about 4% of people with diverticulosis develop diverticulitis. Age is a major factor in how common the pouches are in the first place. Diverticulosis is found in under 20% of people at age 40, around 60% by age 60, and up to roughly 70% after age 80.

When to see a doctor or seek emergency care

Because diverticulitis can occasionally lead to complications such as an abscess, a perforation that spreads infection into the abdomen (peritonitis), or an abnormal connection between organs (a fistula), some symptoms are red flags. Don't wait these out.

Per the Cleveland Clinic, seek urgent care if you notice any of the following:

• Fresh blood in your stool
• Weakness, paleness, or feeling faint
• Painful or unusually frequent urination
• A rigid abdomen that is very sensitive to touch
• Severe or rapidly worsening pain with a high fever

How is diverticulitis treated?

This article is general education, not a treatment plan, but here's the broad picture. Milder cases are often managed with rest, dietary changes, and sometimes antibiotics, while more serious or complicated cases may need hospital care. Diverticulitis is a meaningful health burden in the US, accounting for nearly 200,000 hospital admissions each year and about $2.2 billion in annual health care costs.

Only a clinician can confirm diverticulitis, usually with an exam and imaging such as a CT scan, and rule out other causes of abdominal pain. If your symptoms match what's described here, especially the rapid onset of left-sided pain with fever, reach out to a healthcare provider promptly so you can get the right diagnosis and care.