For most people, COVID-19 symptoms will clear up in a couple of weeks. But researchers are learning more about long COVID-19, also known as post-COVID condition or long-haul COVID-19. Long COVID-19 involves lingering symptoms that can last for weeks or months after the initial diagnosis.

There is no single test to diagnose long COVID-19. People with long COVID-19 have reported a wide variety of symptoms, many of which could also be due to other conditions or underlying health issues. To determine if someone has long COVID-19, a doctor may perform several tests to rule out other diseases.

Long COVID-19 can affect nearly every system in the body, including the lungs, brain, heart, skin, hormones, gastrointestinal tract, and kidneys. It can also cause fatigue and mental health issues. With so many possible symptoms, diagnosing long COVID-19 can be difficult. Health care providers are still learning about people with long-term symptoms of COVID-19 and how to properly diagnose this condition.

Defining Long COVID-19

Most people with acute (short-term) COVID-19 will have symptoms for up to four weeks. Symptoms of acute COVID-19 include difficulty breathing, fever, fatigue, muscle aches, loss of taste, and loss of smell. In severe cases, people with COVID-19 can develop pneumonia and require hospital care.

Long COVID-19 can last for weeks to months. These long-term symptoms can appear in people who had severe symptoms, mild symptoms, or no symptoms during their acute coronavirus infection.

Both the U.S. Centers for Disease Control and Prevention and the U.K. National Institute for Health and Care Excellence define long COVID-19 as symptoms that last for more than four weeks after the initial COVID-19 diagnosis. If symptoms last four to 12 weeks, it is considered ongoing symptomatic COVID-19. When COVID-19-related symptoms continue after 12 weeks with no other detectable cause, it is called post-COVID-19 syndrome (PCS).

According to the World Health Organization, long COVID-19 symptoms occur 12 weeks or more after the initial infection and last for at least two months. The symptoms may be the same or different as those experienced during acute COVID-19, and they may come and go over time.

Do You Have Long COVID-19?

If you are experiencing symptoms 12 weeks after testing positive for COVID-19, or you have developed new symptoms since recovering from COVID-19, you may be experiencing long COVID-19.

For a doctor to diagnose long COVID-19, they first need to determine whether you are currently infected or were previously infected with the virus that causes COVID-19. It is possible to have acute COVID-19, recover, and then contract acute COVID-19 again. This is why COVID-19 vaccines and safety measures are important, even if you have already had COVID-19 once.

Your doctor will also check whether there are any other diseases or conditions that can explain your symptoms. Keeping track of your symptoms using a timeline from when you were infected can help your doctor figure out if you have long COVID-19. It can be helpful to note down all of your symptoms before you visit your doctor.

Testing for past or current COVID-19 infection is usually the first step toward a long COVID-19 diagnosis.

Testing for Current COVID-19 Infection

The virus that causes COVID-19 is called SARS-CoV-2. Researchers can test for active infection with laboratory techniques that detect the genetic material of the virus (ribonucleic acid) from nasal swabs or saliva. Other tests can detect proteins made by the virus called antigens.

Tests may be sent to a lab and take a day or two to process. There are also rapid at-home tests which can tell you if you have COVID-19.

Many people with long COVID-19 will not test positive because they do not have an active infection. Instead, they are still experiencing symptoms due to their body’s response to the coronavirus. Testing for the virus can help rule out a reinfection of acute COVID-19 and point toward the possibility of long COVID-19 instead.

Testing for Previous COVID-19 Infection

Many people did not have access to viral testing in the early days of the COVID-19 pandemic, so they might not know for sure if they had COVID-19 or not. Health care professionals can test if someone has previously been infected by measuring their antibodies.

Antibodies are specialised proteins made by the immune system to attack and fight off pathogens, like bacteria or viruses. When someone has COVID-19, their immune system makes antibodies specific to the virus that stay in the body for a long time after infection. In the case of COVID-19, different antibodies are generated in response to vaccines.

Your doctor can test your blood to see if you have antibodies that target the coronavirus. Having antibodies means you previously had COVID-19, or you received a COVID-19 vaccine.

While antibody tests can be helpful, they have some shortcomings. Antibody levels can decrease over time, and some people do not have strong antibody responses to the virus in the first place. For people who had symptoms of COVID-19, health care providers may assume that they were infected with the virus and perform other tests to diagnose long COVID-19.

Testing To Rule Out Other Health Conditions

Apart from testing for the coronavirus itself, exams are performed to rule out other conditions that may be causing your symptoms.

Physical Exam

To get an idea of your general health and understand your symptoms, doctors can perform a general physical exam. This involves getting your full medical history, including any previous conditions that can cause similar symptoms to long COVID-19.

Your doctor can then also check your blood pressure, heart rate, respiratory rate, oxygen levels, and body temperature. Your doctor may ask you to rate your mental health and physical ability before and after your initial COVID-19 symptoms to understand how your symptoms may be impacting your life. These measurements can help your doctor understand why you are experiencing certain symptoms.

Blood Tests

Different kinds of blood tests can provide information about the health of your heart, kidneys, hormones, muscles, joints, and digestive system. These tests can help a doctor rule out other diseases and identify which parts of the body might be affected by long COVID-19.

Breathing and Exercise Tests

Exercise tests involve measuring your vital signs before and during mild exercise, such as a six-minute walk test or a one-minute sit-to-stand test. Doctors can use a device called a spirometer to measure how much air you’re able to breathe in and out. They can also measure the amount of oxygen in your blood (oxygen saturation) to understand how well your lungs are working.

The Centers for Disease Control and Prevention notes that not everyone should take exercise tests. Some people with long COVID-19 experience post-exertional malaise, or the worsening of symptoms following even mild physical or mental activity. Be sure to communicate all of your physical symptoms — including fatigue — to your doctor so they can prescribe the best tests for you.

Imaging Scans

Several types of imaging scans can help your doctor determine if your symptoms are linked to any abnormalities or organ damage. Whether imaging tests will be useful for you may depend on the results of other tests performed by your doctor.

A doctor may want to look at your chest and lungs, heart, or brain. Imaging technology includes X-ray, ultrasound, magnetic resonance imaging (MRI), or computer tomography (CT) scans. The type of imaging test used depends on what kind of information the doctor hopes to learn.

Ultrasound can be used to look at the chest, or at the joints or abdominal area in people experiencing joint pain or gastrointestinal issues. An echocardiogram creates an image of your heart to help your doctor detect potential heart disease.

Diagnosis for Long COVID-19

If your doctor does not see evidence that you have another disease causing your symptoms, and your symptoms have continued for 12 weeks or more after your initial COVID-19 infection, then your doctor may confirm a long COVID-19 diagnosis.

COVID-19 is still a relatively new condition, and researchers are learning more about the long-term effects. As they do, the pathway to diagnosing long COVID-19 may change. Keeping close track of your symptoms and communicating clearly with your doctor can help you get the care you need.

Talk With Others Who Understand

On myCOVIDteam, the social support network for those recovering from the effects of COVID-19, you can connect with others. Members come together to ask questions, give advice, and share their stories with others who understand.

Are you living with long COVID-19? How did your doctor diagnose your condition? Share your insights in the comments below, or start a conversation by posting on myCOVIDteam.