COVID-19 can cause abdominal discomfort, nausea, and vomiting. As this can make it difficult to tell whether a person has COVID-19 or a stomach bug, the only way to know for sure is to take a COVID-19 test.

The SARS-CoV-2 virus can cause a wide range of symptoms that can vary among individuals. Some of these can mimic the stomach flu or other gastrointestinal (GI) conditions, making it hard to identify the source.

Looking at other symptoms, recent potential exposures, and risk factors can help a person determine what is causing their abdominal discomfort. However, an individual should take a SARS-CoV-2 test if they think that they may have the virus.

Read more to learn about when a stomachache is a sign of COVID-19, why the coronavirus causes GI symptoms, and more.

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COVID-19 is a respiratory condition that is primarily a vascular disease. This means that it affects the blood vessels that circulate blood throughout the body.

The disease usually manifests as a cough, fever, congestion, wheezing, or shortness of breath. In more severe cases, it can cause symptoms such as chest pain.

However, several studies have shown that a significant number of people with COVID-19 develop GI symptoms. These can include a stomachache, diarrhea, nausea, and vomiting.

A large 2020 systematic review looked at the symptoms of people with COVID-19. Of more than 18,000 participants, 11.5% experienced diarrhea, 6.3% experienced nausea and vomiting, and 2.3% experienced abdominal pain.

This means that although GI symptoms are less common in many people with COVID-19, they can occur.

Additionally, these symptoms may be more prevalent in people who are severely ill with COVID-19. A small 2020 study found that two-thirds of individuals had at least one digestive issue upon admission. Diarrhea was the most common, affecting 29.8%, followed by nausea and vomiting (22%) and abdominal pain (14.9%).

One reason why people consider COVID-19 to be a respiratory disease may be because respiratory symptoms appear earlier.

In a 2020 study, researchers analyzed 55,924 confirmed COVID-19 cases and found that respiratory symptoms are more likely to appear earlier in the disease. Nausea and diarrhea usually come later.

However, each person’s symptoms can progress differently. While some people may have GI symptoms, others may have none at all.

Symptoms alone are only suggestive, and they cannot prove that a person does or does not have COVID-19.

The most effective way to distinguish food poisoning from COVID-19 is to take a test for SARS-CoV-2. However, even these tests are not perfect. To get the most reliable results, a person should consider retesting a few days after a negative test.

A person can also determine whether they have COVID-19 by considering several factors, including:

  • If everyone in the household recently ate the same food and feels sick, food poisoning might be the culprit.
  • If several recent contacts develop symptoms, they and the person may have COVID-19.
  • If a person only has GI symptoms, COVID-19 is less likely, though still possible.

A person can also evaluate the symptoms:

  • Fever: Although food poisoning can also cause it, a fever is often the first symptom of COVID-19.
  • Cough and respiratory issues: Food poisoning does not cause breathing problems or coughing. However, it can cause fatigue and chills.
  • Neurological symptoms: COVID-19 can cause the loss of smell and taste. Food poisoning can cause headaches, but it does not cause changes in smell and taste.
  • Course of illness: GI symptoms that appear after other symptoms, such as a cough or fever, are more consistent with COVID-19 than with food poisoning.

Although it has affected nearly all aspects of life, SARS-CoV-2 is a relatively new and changing virus, and there is still a lot researchers do not understand about it. This includes why people get the symptoms they do and what causes some people to get very ill while others develop few or no symptoms.

Experts are still not entirely sure why the virus causes GI symptoms in some people, but research is beginning to investigate the link.

According to a 2021 paper, SARS-CoV-2 may attack the GI tract, triggering digestive issues in some people.

The virus uses the body’s angiotensin converting enzyme 2 (ACE2) to penetrate cells. There are large amounts of this enzyme in the GI tract, potentially providing a pathway for SARS-CoV-2 into the digestive system.

Some people also experience persistent digestive symptoms after recovering from COVID-19.

A 2021 meta-analysis found that after having COVID-19, 3.19% of people experienced persistent vomiting while 4.12% had prolonged diarrhea. Although the cause is unclear, it is possible that these lasting symptoms could be due to the virus damaging cells in the digestive system.

During the COVID-19 pandemic, stretched medical services worldwide have made it more difficult to receive medical care.

Some doctors will not see people with a fever or other, mild COVID-19 symptoms. They may treat people virtually and admit them to the hospital if the symptoms worsen.

If a person’s symptoms are due to food poisoning, they likely will not require medical care. Most bouts of food poisoning resolve on their own with supportive, at-home measures.

Likewise, mild cases of COVID-19 usually do not require medical treatment. People can manage their symptoms with rest, fluids, and pain relief medications at home.

People who think they have COVID-19 or food poisoning should consider contacting a doctor if their symptoms do not improve. In many cases, a doctor may be able to help diagnose the issue via a telehealth visit.

An individual should contact a doctor for any GI issues that cause:

  • bloody diarrhea
  • dehydration
  • inability to keep food or fluids down
  • diarrhea lasting longer than 3 days
  • a fever, measured orally, higher than 102ºF

They should go to the emergency room if they develop:

  • trouble breathing or persistent chest pain
  • pale or blue-colored lips or hands
  • new confusion or an inability to wake or stay awake

In addition to a fever and cough, COVID-19 can cause gastrointestinal symptoms in some people. As a stomachache, diarrhea, and vomiting are also symptoms of a stomach bug, it can be difficult to tell the two diseases apart.

The only way to know for sure is to take a SARS-CoV-2 test.

People with symptoms of COVID-19 or food poisoning should isolate from others, drink plenty of fluids, rest, and contact a doctor if their symptoms worsen.