Should You Retest After Testing Positive for COVID-19—And if So, When?

The CDC says you can retest yourself after your five-day isolation period, but it's not necessary. Here's what infectious disease experts think of that guidance.

A positive COVID-19 test can be jarring, but what to do after receiving one is clear: Isolate—specifically for five days, whether you're showing symptoms or vaccinated. And if you absolutely have to be around other people (say, if you share a home with others who are COVID-negative), you should wear a well-fitted mask.

The guidance for when you can (or whether you should) test yourself again after receiving a positive result, however, is a bit less straightforward.

In short, retesting is optional and only necessary if you have severe illness or are immunocompromised. If you retest, wait until the end of your five-day isolation period and until you're fever-free for 24 hours without a fever reducer to take an at-home antigen test.

Some people, either in hopes of cutting quarantine corners or out of curiosity about their condition, have taken to tracking their COVID-19 status by testing daily with at-home antigen tests. But doctors warn against testing yourself for the virus every day—not necessarily because it's harmful, but because it's likely unhelpful.

Here, Health digs into what the official guidance from the Centers for Disease Control and Prevention (CDC) said regarding when to retest after a positive COVID-19 result and what experts in the field most commonly suggested.

When Should You Retest After Testing Positive for COVID? Medical worker wearing personal protective equipment doing corona virus swab on female patient - Covid19 test and health care concept
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What Happens if I Test Positive for COVID-19?

If you receive a positive result after testing for COVID-19 and have symptoms—including fever, cough, fatigue, headache, sore throat, or new loss of taste or smell, among others—the CDC recommended you isolate yourself at home for five days regardless of whether you are vaccinated against the virus.

If you are asymptomatic at the time of your test and later develop symptoms within 10 days, you should restart your five-day isolation.

You should wear a mask if you have to be around others, stay as separate from others as possible, and avoid sharing personal items during those five days. And if you develop severe symptoms, you should see a healthcare provider.

The CDC advised that you may end your isolation after day five if your symptoms improve and you are fever-free for 24 hours without the use of a fever reducer. But some people may wonder whether retesting after a positive COVID-19 test is necessary.

CDC Guidelines for Retesting After a Positive COVID-19 Test

After a five-day isolation period, if your symptoms subside, the CDC said retesting yourself is an option, not a requirement.

"If you have access to antigen tests, you should consider using them," the CDC guidelines read. "With two sequential negative tests 48 hours apart, you may remove your mask sooner than day 10."

But if you do not have access to an antigen test or do not retest after ending your isolation—and your symptoms subside—you should continue to wear a mask through day 10.

That guidance differs a bit if you were severely ill from COVID-19 or if you have a weakened immune system. In that case, the CDC said you might require additional viral testing—molecular or antigen tests—to determine if and when it's safe to be around others. But in that case, the best course of action is to talk with your doctor to determine a testing plan.

Experts on Retesting After a Positive COVID-19 Test

If you find yourself feeling confused over the CDC guidelines for self-quarantine and isolation, you're not alone. The president of the American Medical Association (AMA), Gerald E. Harmon, MD, discussed the matter on January 5, 2022.

"A negative test should be required for ending isolation after one tests positive for COVID-19," Dr. Harmon shared in a statement. "Reemerging without knowing one's status unnecessarily risks further transmission of the virus."

According to the AMA, approximately 31% of people remain infectious after the recommended five-day isolation period following a positive COVID-19 test. And Dr. Harmon said that could result in "potentially hundreds of thousands of people" returning to work or school while they're still contagious.

However, although the CDC guidelines may be confusing or conflict with experts' opinions, there may be a couple of reasons to retest after a positive COVID-19 test—including if you develop new symptoms or if your employer asks.

Should I Restest After a Positive COVID-19 Test if New Symptoms Develop?

One definite reason that you should retest after a positive COVID-19 test is if you were on the mend and later developed new symptoms.

According to the CDC, you should receive a new antigen or PCR test if you experience new symptoms if it has been longer than three months after your initial infection date. If it has been less than three months since that date, you should consult your healthcare provider. If they cannot determine another reason for your symptoms or suspect reinfection, it might be a good idea to retest.

Should I Retest After a Positive COVID-19 Test if My Employer Asks?

The CDC does not advise employers to mandate negative COVID-19 tests after employees complete their recommended five-day isolation. However, per the CDC, employers should expand the number of free testing sites to make retesting, if necessary, widely available and limit the spread of the virus.

Retesting To Confirm a Negative or Positive COVID-19 Test

That said, even an additional antigen test after isolation may only be so helpful. That's because antigen tests, more so than PCR tests, are prone to false negatives.

"A negative antigen test at five days [after testing positive] tells you that the amount of virus present in your nose, saliva, or wherever you sampled from is low enough not to cause a positive test," Clare Rock MD, infectious disease physician, epidemiologist, and associate professor of medicine at the Johns Hopkins University School of Medicine in Baltimore, told Health.

"It does not necessarily mean you are not still infectious to others, which is why it's very important to wear a mask," noted Dr. Rock.

To make things even more confusing: Let's say you still get a positive COVID-19 test result, even after 10 days of isolation, which may not tell you everything you need to know.

"Some people persist in getting a positive result many days after infection when in theory they are considered noninfectious," Cheryl G. Healton, DrPH, dean of the School of Global Public Health at New York University, told Health.

Both antigen and PCR tests can detect dead virus fragments that may remain in the upper airway, even after you're no longer infectious, Dr. Healton explained.

The bottom line: You should retest to confirm a negative COVID-19 test and previously had close contact with someone who tested positive, frequently interact with other individuals at work or at school, or currently have symptoms of COVID-19—per the Alameda County Health Care Services Agency Public Health Department.

So, What Should You Do With This Information?

Though the CDC guidelines are admittedly hard to interpret, they're the best course of action. If you've tested positive for COVID-19 (or if you have symptoms), isolate for at least five days or until you do not have a fever for 24 hours and your symptoms subside. Then, continue to exercise caution by wearing a mask around others until 10 days have passed since your first positive test or symptom.

"The CDC guidance aligns with clinical experience that shows the bulk of people who are post-symptomatic five days after symptom onset are not actively infectious," said Dr. Healton. "The fact that tests can remain positive post-infection may be one reason why [the CDC] emphasized time [over testing to end isolation]."

If you would like to use an antigen test at the end of your five-day isolation period (and you have one available to you), you can go ahead and do that, but no more frequently than every three days after your initial five-day isolation, said Dr. Rock, to avoid any false negative or positive tests.

At the end of the day, no test (or CDC guideline) is reliable enough to tell you with 100% accuracy whether you're still contagious, which is what retesting is really all about.

"Being cleared for normal activities by your health care provider is the best course," Dr. Healton said. And the same goes for wearing a mask out in public. The most protective ones—N95 respirators—help to best shield you and others from viral particles.

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.

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