Why Diarrhea Symptoms Happen With COVID-19

Although COVID-19 is largely regarded as a respiratory illness, diarrhea is a common gastrointestinal (GI) symptom that can occur during the early stages of the infection.

Some studies suggest that up to half of all people with COVID will experience loose, watery stools, generally mild and self-limiting (clearing up on their own). In some people, diarrhea may be the only symptom. Others may experience persistent diarrhea as a feature of long COVID (a condition in which COVID symptoms persist for more than 12 weeks after the infection has cleared).

The infection itself can trigger diarrhea. Emotional distress and certain medications used to treat COVID can also cause watery poop.

This article explains the various causes of diarrhea in people with COVID-19 and whether diarrhea is a sign of a milder or more severe infection. It also offers tips on how to treat COVID-related diarrhea and when it is time to see a healthcare provider.

Cause of Diarrhea in COVID-19

GI symptoms are a common feature of early COVID infection, affecting 1 in 5 people overall. Of these, nearly 70% will experience diarrhea either on its own or with other GI symptoms.

Diarrhea is by far the most common COVID-related GI symptom and often the most debilitating. It has several possible causes, some of which overlap.

COVID Infection

COVID-19 is caused by a strain of coronavirus called severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2), The virus causes infection by latching onto a protein on the surface of cells called angiotensin-converting enzyme 2 (ACE2) and using it to "unlock" and enter the cell.

Though the highest density of ACE2 is in the lungs and airways, the lining of the stomach and intestines is also rich in ACE2.

When COVID affects the digestive tract, it can set off a chain of events that leads to diarrhea by:

• Triggering inflammation that speeds up gut motility (the rhythmic, involuntary contractions that move stool through the intestines)
• Causing tissue damage that increases gut permeability (the release of water from the intestines)
• Disrupting the normal balance of microorganisms in the gut (intestinal flora) that aid with digestion (referred to as gut dysbiosis)

This trio of events can create the "perfect storm" for diarrhea and other COVID-related GI symptoms such as:

• Nausea and vomiting
• Abdominal pain
• Loss of appetite
• Belching
• Acid reflux
• Heartburn
• GI bleeding

Psychological Distress

Stress and anxiety are independently linked to diarrhea in people with COVID-19. This is evidenced by studies in which nearly 30% of people who tested negative for COVID during the height of the pandemic experienced diarrhea as a result of COVID-related stress.

While many of those fears have since eased, they are still known to trigger diarrhea in people with long COVID.

A 2022 study published in the journal Gastroenterology found that mental health issues like anxiety and sadness independently increased the odds of diarrhea and other GI symptoms by sixfold in people with long COVID compared to counterparts with no mental health issues.

Medications

Some of the medications authorized for the treatment of COVID-19 can also cause diarrhea, potentially making symptoms worse for people with COVID-related diarrhea.

Diarrhea is a common side effect of the following COVID-19 medications:

• Actemra (tocilizumab)
• Olumiant (baricitinib)
  
• Paxlovid (nirmatrelvir and ritonavir)

If prescribed treatment for COVID-19, advise your healthcare provider if you have diarrhea or any other GI symptoms. Another Food and Drug Administration (FDA)–approved COVID drug called Veklury (remdesivir) is not associated with diarrhea.

Effect of COVID-19 on Diarrhea 

It is debated as to whether diarrhea significantly impacts the risk of morbidity (illness) or mortality (death) in people with COVID. While some studies suggest that GI symptoms are a sign of a milder COVID infection, others have found that GI symptoms can lead to worse outcomes by delaying essential treatment.

A single-center study from New York Presbyterian Hospital reported that among 1,059 people diagnosed with COVID, GI symptoms were associated with a higher risk of hospitalizations but a 27% lower risk of intensive care unit (ICU) admissions and a 50% lower risk of death.

The same was not seen with another single-center study from Rush University Medical Center in Chicago. Among the 1,002 people included in this study, GI symptoms were associated with a fivefold increased risk of hospitalization, a 2.5-fold increased risk of ICU admission, a twofold increased risk of intubation, and a 2.5-fold increased risk of acute respiratory distress syndrome (ARDS).

Although the differences in findings may be hard to explain—particularly given that both studies evaluated patient data from March 2020 to April 2020—the Rush University investigators suggested that a more severe COVID variant may have been involved.

Timing and Duration of COVID-Related Diarrhea

The GI symptoms of COVID often precede the respiratory symptoms of the illness by several days. The study from Rush University Medical Center reported that 22.4% of people diagnosed with COVID had diarrhea or other GI issues as their first symptom.

The severity and duration of COVID-related diarrhea can vary. While most cases are mild and self-limiting, there may, in rare instances, be severe cramping, rectal bleeding, and bloody stools.

On average, a person with COVID-related diarrhea will have watery stools three to four times daily for between three and five days. Severe cases can last as long as 14 days and typically require hospitalization.

Diarrhea can become persistent in people with long COVID. According to a 2021 study in Lancet Gastroenterology and Hepatology, 1 in 6 people with long COVID experience diarrhea along with a host of other GI symptoms like nausea, acid reflux, belching, and vomiting.

While it is unclear how long these symptoms can last, a 2023 report in the National Review of Microbiology suggests the GI symptoms tend to resolve fully (and faster) than many other long COVID symptoms. Even so, imbalances in the intestinal flora can persist for 14 months or longer, further contributing to chronic or recurrent diarrhea.

Treatments to Manage COVID-Related Diarrhea 

There are no specific guidelines for the treatment of COVID-related diarrhea. Mild infections are typically treated at home with a combination of diet, lifestyle changes, and home remedies.

There are things that may help if you have COVID-related diarrhea:

• Drink plenty of fluids to avoid dehydration.
• Eat bland foods, steering clear of spicy, salty, or fatty foods.
• Take a probiotic supplement (especially Lactobacillus probiotics).

In the event of severe dehydration, intravenous (IV) fluids may need to be administered in a hospital to replace lost fluids and electrolytes.

Antidiarrheal medications might delay clearing the virus from the gut. Therefore, before taking these drugs, ask a healthcare provider about the risks and benefits of taking them.

When to Call a Healthcare Provider

Whatever the cause, diarrhea should never be ignored if it is persistent or severe. Left untreated, diarrhea can lead to severe dehydration and complications like seizures, kidney failure, shock, or death,

Children, older adults, and people with compromised immune systems are especially vulnerable.

Seek immediate medical care if you have any of the following symptoms:

• Signs of severe dehydration (including extreme thirst, fatigue, dizziness or fainting, rapid pulse, rapid breathing, not passing urine for eight hours)
• Diarrhea that persists for more than two days in adults or more than 24 hours in children
• Severe pain in the abdomen or rectum
• A fever of 102 degrees F or higher
• Stools containing blood or pus
• Black or tarry stools

Diarrhea can be especially dangerous in newborns and infants.

Summary

Vomiting and other gastrointestinal symptoms (like nausea, diarrhea, and abdominal pain) may be early signs of COVID-19 and may even precede the respiratory symptoms of COVID by one or more days. Though the symptoms tend to last from a few days to a week in people with mild COVID-19, they can sometimes persist for months in people with long COVID.

COVID-19 can cause diarrhea by attacking the lining of the digestive tract in the same way that it attacks the lining of the respiratory tract. Psychological distress and certain medications used to treat COVID can also cause digestive symptoms.