When Does Diarrhea Require a Medical Evaluation?

Virtually everyone experiences diarrhea from time to time: Loose, watery stools are a normal immune system response to food poisoning and many common infections; they’re also a routine side effect of antibiotics and gastrointestinal system food intolerances. 

In most cases, diarrhea is acute, meaning it only lasts for a few days and resolves by itself. But when runny bowel movements persist for longer than a few days — or when they become an ongoing, chronic problem — it may be a sign of a more serious underlying concern. 

Here, board-certified gastroenterologist Dr. Sam Weissman discusses the difference between acute, persistent, and chronic diarrhea and explains when it warrants immediate medical care or an in-depth professional evaluation.

Understanding diarrhea

Diarrhea is defined as having bowel movements that are more liquid than normal, occur more often than normal, and expel a much higher volume of stool than normal. Specifically, having diarrhea means passing three or more loose or watery stools a day. 

Bowel movements are roughly 25% protein, fat, mucus, dietary fiber, and about 75% water. As solid waste travels through your upper gastrointestinal (GI) tract, it gathers the fluids and electrolytes that are secreted during digestion. Normally, your lower GI tract absorbs excess fluid before your waste reaches your colon so that your exiting stool is firm and solid.

With diarrhea, the digestive process is accelerated or intensified. It may occur when your upper GI tract secretes excessive fluids and electrolytes, when your lower GI tract doesn’t absorb excess fluid from the rush of waste quickly enough, or both.

Acute, persistent, or chronic? 

Diarrhea is classified based on its duration: 

Acute diarrhea

Acute diarrhea lasts for one or two days and resolves on its own. As the most common type of dysentery, there are about 179 million cases of acute diarrhea in the United States each year. 

Acute diarrhea is typically caused by some type of infection. It may be caused by food-borne pathogens like salmonella and E. coli or a parasitic infection like cryptosporidium or Giardia lamblia, which can be contracted through contaminated drinking water, food, or recreational water.

In many cases, acute diarrhea results from a viral infection such as rotavirus, norovirus, or viral gastroenteritis (stomach flu).

Persistent diarrhea

Persistent diarrhea continues longer than acute diarrhea but resolves before it becomes a chronic problem. Most cases of persistent diarrhea last for 2 to 4 weeks.

The same bacterial, viral, and parasitic infections that trigger acute diarrhea can lead to persistent diarrhea when they don’t resolve quickly. Persistent diarrhea is also a common side effect of certain medications, including some antibiotics.

Chronic diarrhea

Diarrhea that lasts for longer than four weeks is considered chronic. Chronic diarrhea may be continual, or it may come and go. Long-lasting diarrhea may be a sign of undiagnosed food intolerance, or it may be a symptom of a serious bowel disorder such as Chron’s disease, ulcerative colitis, or irritable bowel syndrome (IBS). 

A variety of prescription drugs can also cause chronic diarrhea, including certain acid reflux and blood pressure medications.

When to see a doctor about diarrhea

Severe diarrhea — whether acute or persistent — can quickly lead to dehydration. When your body becomes dehydrated, it doesn’t have the fluids and electrolytes it needs to work properly. Dehydration is particularly dangerous for babies, children, older adults, and people with compromised immune systems. Left untreated, dehydration can be deadly. 

Immediate care

Seek immediate medical care for a baby or child with diarrhea that doesn’t improve within 24 hours. It’s especially important to go to the doctor if their diarrhea is accompanied by:

• A high fever (at or above 102° F)
• No wet diaper for three or more hours
• Dark urine; urinating less than usual
• A dry mouth; crying without tears
• Sunken appearance to eyes or cheeks
• Unusually sleepy, lethargic, or irritable 
• Black or bloody bowel movements

Seek prompt care for an older adolescent or adult with diarrhea that lasts longer than two days without improvement. Go to the doctor as soon as possible if diarrhea is accompanied by:

• A high fever (at or above 102° F)
• Severe abdominal or rectal pain
• Bloody or black bowel movements

Urgent medical care is also critical when diarrhea is accompanied by signs of dehydration. This may include excessive thirst or a dry mouth, little to no urine (or dark yellow urine), severe weakness, dizziness, or lightheadedness.

Medical evaluation 

Diarrhea that persists or becomes chronic always requires a medical evaluation. Even if it doesn’t cause dehydration, long-lasting diarrhea can lead to malabsorption, a condition in which your small intestine doesn’t absorb nutrients from your food. 

When you don’t get nutrients from your diet, you can become malnourished. Persistent or chronic diarrhea accompanied by bloating, gas, and weight loss can indicate malabsorption.

If you have persistent or chronic diarrhea, don’t delay. Call 609-793-9375 to reach our office in the Brighton Beach neighborhood of Brooklyn, New York, or use the online booking feature to schedule a visit at Sam Weismann, MD, any time.