COVID-19 and Gastrointestinal Symptoms

Written by Stephanie Watson, Alexandra Benisek
Medically Reviewed by Melinda Ratini, MS, DO on October 30, 2024
7 min read

COVID-19 may be best known for causing respiratory symptoms, such as fever, dry cough, sore throat, and shortness of breath. But stomach upset can also occur with the latest COVID-19 variants.
 

During the pandemic, an estimated 50% of people with COVID have gastrointestinal (GI) symptoms such as nausea, diarrhea, vomiting, or belly pain. These may be the first symptoms of the infection. For some people, they’re the only symptoms.

Once a virus infects your body, it can destroy healthy cells and make multiple copies of itself. The virus causing COVID mainly attacks the cells lining your airways. This makes it hard for you to breathe and can lead to pneumonia. But researchers think the illness also may harm your digestive tract and liver.

In your lungs, the virus attaches to receptors the way a key fits into a lock. The same receptors are also in your intestines. When COVID attaches to the receptors in your gut, it makes your body release chemicals that promote inflammation. The inflammatory chemicals attack the protective barrier around your stomach, esophagus, and small intestine, causing damage that leads to symptoms like nausea, vomiting, and diarrhea.

Those with digestive symptoms are more likely to have a positive stool test for the coronavirus, which means they have SARS-CoV-2 RNA in their poop. It also takes them longer to clear the virus from their bodies, compared to those without gastrointestinal symptoms.

The following are some of the most commonly noticed COVID gastrointestinal symptoms and their possible causes.

Belly pain is a less common GI symptom of COVID than diarrhea and nausea, but it can happen. The most likely cause is inflammation in the intestine from the infection. Sometimes, belly pain happens in people with a severe COVID infection. 

This symptom also can be from liver damage caused by the virus. Because liver damage could be serious, get checked by your doctor if you have belly pain and symptoms such as:

  • Yellow skin and eyes
  • Dark-colored pee
  • Fever
  • Tiredness
  • Weight loss
  • Nausea and vomiting
  • Diarrhea

Up to half of people with COVID have loose, watery poop. Diarrhea also affects about 30% of people with long COVID. This symptom could predict that you’ll have a longer infection. People who have diarrhea with long COVID are more likely to still have COVID symptoms two years later.

Researchers think diarrhea happens for a couple of reasons. First, the virus directly infects intestinal cells. Second, inflammation from COVID irritates the intestine.

Some of the medicines that treat COVID cause diarrhea as a side effect, including antibiotics and antiviral drugs. Antibiotics aren’t the main treatment for COVID because they kill bacteria, not viruses. But COVID can sometimes lead to a bacterial infection that needs treatment. Antibiotics cause diarrhea by changing the balance of good and bad bacteria in your gut.

Usually, COVID-related diarrhea is mild and goes away within two to six days. But sometimes, it can be severe. If diarrhea causes dehydration, you may need treatment with IV fluids in a hospital.

About 1 in 5 people with COVID have nausea and vomiting. Scientists think that when the virus attacks the digestive tract, it causes inflammation and releases hormones that stimulate the vagus nerve. This nerve sends information to your brain that triggers nausea. Nausea usually goes away in a few days.

It’s common to lose your appetite when you’re sick with COVID. Being sick on its own doesn't make you feel like eating much. But a common symptom of COVID is loss of taste and smell, which can also lower your appetite. If you can’t smell or taste food, you may not want to eat as much. Appetite loss could lead to weight loss and malnutrition, so it's important to eat even if you don't feel like it.

Other digestive system symptoms that may be linked to COVID are:

  • Weight loss
  • Bleeding from the rectum
  • Heartburn
  • Acid reflux

Your intestines are home to trillions of tiny organisms such as bacteria, viruses, and fungi. Scientists call this microscopic city the gut microbiome, and it helps keep your immune system healthy.

Changes in your microbiome can contribute to disease. Research shows that COVID may alter the number and types of organisms in the microbiome. People with COVID have more harmful germs and fewer helpful ones in their microbiome. This imbalance could lead to more inflammation and more severe COVID symptoms. Studies are looking at whether probiotics — live bacteria and yeasts that are good for your body — might help treat COVID.

Having long COVID means that you still have symptoms three months or longer after you first got the infection. The most common symptoms are tiredness, trouble breathing, changes in heart rhythm, brain fog, and muscle pain. But some people with long COVID have chronic diarrhea and belly pain.

Experts don’t know exactly what causes long COVID GI symptoms. One possibility is that the virus alters signals that help the brain and gut “talk to” each other. Changes in brain-gut communication might lead to diarrhea, stomach pain, and constipation. Inflammation in the gut and the emotional effects of having long COVID may also lead to GI symptoms. The more severe COVID infection you have, the more likely you are to get GI symptoms.

If you have diarrhea, nausea, or vomiting, it doesn't mean that you have COVID. But it's wise to pay extra attention to your symptoms during this pandemic, especially if you have a health condition that raises your infection risk or if you live in an area where coronavirus is widespread.

Stay home. Most people who test positive for the coronavirus get mildly sick and get better without treatment. Avoid going out unless you must, such as for urgent medical visits.

Have a “sick” bedroom and bathroom. If you can, use a separate bathroom for yourself if you live with others to prevent spreading illness through your poop.

Wash your hands often. Using soap and water for at least 20 seconds is best, especially after you use the bathroom, blow your nose, or sneeze, and before eating or cooking. The next best option is a hand sanitizer with at least 60% alcohol.

Clean and disinfect surfaces regularly. This includes the toilet seat and flush handle, bathroom doorknobs, phones, counters, and other things you touch often.

Drink lots of fluids. If you have diarrhea or are vomiting, it's important to replace the lost fluids. An oral rehydration solution from the drugstore is best because it has salt and sugar that your body loses in diarrhea. Or you can sip watered-down fruit juices or soft drinks, along with salted crackers and broths.

Eat a bland diet. Try foods such as bananas, white rice, applesauce, and toast, which can help limit your urge to poop and replenish carbohydrates that your body needs. You can also try oatmeal, boiled or baked potatoes, and baked chicken without skin.

Antiviral medicines such as nirmatrelvir/ritonavir (Paxlovid) and remdesivir (Veklury) help make the infection less severe, but they don’t treat GI symptoms specifically. Which treatment you use depends on your symptoms. These medications are only by prescription and you have to start taking them within five to seven days of your first symptoms. 

There are things you can do at home to manage your symptoms.

For nausea and vomiting:

  • Eat small meals and snacks.
  • Drink extra water and other fluids to prevent dehydration.
  • If the smell of cooking makes you sick, eat foods cold or at room temperature.

For diarrhea:

  • Drink extra water and fluids like broth and juice to stay hydrated.
  • Eat a bland diet, such as bananas, rice, and toast.
  • Take medicines such as loperamide (Imodium) or bismuth subsalicylate (Pepto Bismol)

For constipation: 

  • Add more fiber to your diet from fruits, vegetables, bran, and beans.
  • Take a fiber supplement like Metamucil or Citrucel.
  • Drink water and naturally sweetened fruit juice to make your poop softer and easier to pass.

These medicines treat COVID GI symptoms:

  • Prescription medicines metoclopramide (Reglan) and ondansetron (Zofran) help with nausea.
  • Imodium and Pepto Bismol treat diarrhea.
  • MiraLAX or Dulcolax help manage constipation.

Although probiotics aren’t proven to treat COVID GI symptoms, they may help by keeping your gut and immune system healthy overall. You can get these helpful bacteria from foods such as yogurt, kefir, kimchi, and sauerkraut. Or ask your doctor about taking a probiotic supplement.

If your stomach troubles are due to a GI bug or food poisoning, you usually should feel better within 48 hours. If you don't, call your doctor. It could be a more serious bacterial infection or an early sign of COVID. You should also reach out to them immediately if you:

  • Are dehydrated. Signs include dark urine, extreme weakness, a dry mouth and tongue, and dizziness.
  • Have diarrhea that is bloody or black, or severe belly pain.
  • Are feverish, coughing, or feeling short of breath. Call 911 if you are having chest pain or trouble breathing.

Call your doctor right away if a child has diarrhea or a fever.

 

COVID can cause GI symptoms such as nausea, vomiting, diarrhea, and belly pain. Studies show that the virus changes the balance of helpful and harmful germs in the gut. You can manage COVID-related GI symptoms by drinking more fluids, eating a bland diet, and taking over-the-counter medicine if needed.

How long do GI symptoms last with COVID?

GI symptoms usually go away after a few days. But if they’re part of long COVID, these symptoms could last more than three months.

Do gastrointestinal symptoms predict the outcomes of COVID infection?

There is evidence that people with GI symptoms like belly pain and diarrhea are more likely to have a severe COVID infection.