The rundown on diarrhea

Everyone deals with diarrhea at some time. Episodes are often minor, albeit unpleasant, experiences. Other times, they turn into recurring mad dashes to the bathroom with no relief in sight.

So, when is diarrhea "normal," and when should you get checked out?

"Diarrhea is your body saying something is wrong, and while it usually is not a cause for concern, you should still monitor when it occurs, how often, and its severity, as it could be a sign of a more serious digestive issue," says Dr. Kyle Staller, a gastroenterologist with Harvard-affiliated Massachusetts General Hospital.

Acute problems

Most episodes of typical diarrhea are acute — that is, short-term — and they resolve on their own. People usually have loose, watery stools with cramping and urgency. They also may have a temporary low-grade fever and fatigue.

One common cause is a group of viruses known as noroviruses. Another is exposure to toxins produced by bacteria like Escherichia coli (E. coli) through contaminated food or water. (Although people often refer to acute diarrhea as stomach flu, these viruses and toxins are not related to the influenza virus.)

According to Dr. Staller, most people with acute diarrhea recover by allowing the illness to run its course. "Let your system do its work and naturally eliminate the invaders," he says.

The frequency of bathroom trips should begin to decrease after a few days, and the diarrhea should be gone within five days. Be sure to drink a lot of fluids — water and low-sugar sports drinks are ideal — to replace the liquid you are losing and avoid dehydration.

Over-the-counter products that contain the active ingredients loperamide (Imodium) or bismuth subsalicylate (Pepto-Bismol, Kaopectate) can help reduce the frequency of loose, watery stools and ease cramping. "Take them as directed, but avoid them if you have a fever or bloody diarrhea," says Dr. Staller.

Once the diarrhea has receded, ease back into regular eating. For the first few days, Dr. Staller recommends following a BRAT diet — Bananas, Rice, Applesauce, and Toast. The bananas bind the stool, slowing the movement, while white rice, applesauce, and dry, white toast are low in fiber and easily digested.

When to seek help

In some situations, you should seek immediate medical care for your diarrhea. For instance, even if your symptoms just started, call your doctor if you experience bloody diarrhea, severe abdominal pain, or a high fever. These symptoms are uncommon with a viral infection.

Another such circumstance is when diarrhea persists for longer than a week or two. "Persistent diarrhea always should be examined to see if there's an obvious trigger or underlying problem," says Dr. Staller. Although persistent episodes often resolve without an answer, your doctor will begin considering causes different from the ones that trigger acute diarrhea.

For example, your doctor will want to know if you have recently taken antibiotics or been hospitalized. If yes, he or she can order a stool test to check for infection with the bacterium Clostridioides difficile (C. diff), which can be contracted during hospital stays or emerge after a course of antibiotics.

Your doctor also will ask about your recent travels to see if you might have picked up a bacterium or parasite from contaminated food or water.

Diet and medication

Your doctor will inquire about your dietary habits, as persistent diarrhea could be related to undiagnosed lactose intolerance (difficulty digesting milk sugar) or celiac disease (trouble digesting gluten in wheat products).

If one of these is suspected, your doctor may recommend tests to confirm the diagnosis and help design an elimination diet that removes possible trigger foods to see if it resolves the issue.

Also, make sure your doctor knows what medications you are taking. Diarrhea can be a side effect of several prescription drugs, including some used to treat blood pressure or heart problems, and certain over-the-counter remedies, like antacids containing magnesium.

The characteristics of your stool could provide insight as well. Is it just watery, or is there blood and mucus? Blood and mucus usually indicate inflammation of the colon, which could be from a bacterial or parasitic infection or an inflammatory bowel disease (ulcerative colitis or Crohn's disease).

Based on your answers, your doctor will decide on next steps, such as a blood test for anemia and inflammation markers, a stool culture, and an abdominal CT scan. Your doctor may also recommend a colonoscopy.

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