A positive COVID-19 test can be jarring, but what to do after receiving one is clear: Isolate—specifically for five days, whether you are showing symptoms or vaccinated. Wear a well-fitted mask if you absolutely have to be around other people (say, if you share a home with others who test negative for COVID-19).
The guidance for when you can test yourself again after receiving a positive result is a bit less straightforward.
In short, retesting is optional and only necessary if you have a severe illness or weak immune system. Wait until the end of your five-day isolation period and until you are fever-free for 24 hours without a fever reducer to take an at-home antigen test.
Some people, either hoping to cut corners or out of curiosity about their condition, have tracked their COVID-19 status by testing daily with at-home antigen tests. Experts warn against testing yourself for COVID-19 daily—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) says regarding when to retest after a positive COVID-19 result and what experts in the field most commonly suggest.
The CDC advises that you isolate at home for five days—regardless of whether you are vaccinated—if you test positive for COVID-19 and have symptoms. Day 0 marks the start of your symptoms, no matter when you test positive. Then, day 1 is the first full day after your symptoms begin.
COVID-19 symptoms may include:
- Difficulty breathing
- Gastrointestinal symptoms (i.e., diarrhea, nausea, or vomiting)
- Muscle aches and pains
- New loss of sense of smell or taste
- Runny or stuffy nose
- Sore throat
Restart your five-day isolation if you do not have symptoms at your test and later develop symptoms within 10 days. Consult a healthcare provider if you develop severe symptoms.
Of note: Wear a mask if you must be around others, stay as separate from others as possible, and avoid sharing personal items during those five days.
According to the CDC, you may end your isolation after five days if your symptoms improve and you are fever-free for 24 hours without using a fever reducer. Symptoms like a new loss of sense of smell or taste may last for as long as several months after infection. You can end isolation if your senses have not returned to normal.
Retesting after your five-day isolation period is not required if your symptoms subside.
“If you have access to antigen tests, you should consider using them,” according to the CDC guidelines, updated as of May 2023. “With two sequential negative tests 48 hours apart, you may remove your mask sooner than day 10.”
Continue to wear a mask through day 10 if your symptoms subside but do not have access to an antigen test or do not retest.
That guidance differs a bit if you were severely ill from COVID-19 or have a weak immune system. In those cases, the CDC says you might require additional testing to know if being around others is safe. Talk with a healthcare provider to figure out a testing plan.
If you are confused about the CDC isolation and retesting guidelines, you are not alone.
“A negative test should be required for ending isolation after one tests positive for COVID-19,” Gerald E. Harmon, MD, then president of the American Medical Association (AMA), shared in a statement on January 5, 2022. “Reemerging without knowing one’s status unnecessarily risks further transmission of the virus.”
According to the AMA, about 31% of people who test positive for COVID-19 remain infectious after their five-day isolation periods. As a result, “potentially hundreds of thousands of people” return to work or school while they’re still contagious, noted Dr. Harmon.
The CDC guidelines may be confusing or conflict with experts’ opinions. Still, there may be a couple of reasons to retest after a positive COVID-19 test, including if you develop new symptoms or your employer asks.
One definite reason to retest after a positive COVID-19 test is if you were on the mend and later developed new symptoms.
COVID-19 reinfection can occur within 90 days of your initial infection. Consult a healthcare provider if it has been less than three months since that date. Retesting might be a good idea if they cannot determine another reason for your symptoms or suspect reinfection.
The CDC does not advise employers to mandate negative COVID-19 tests after employees complete their five-day isolation.
In contrast, the CDC recommends that employers expand the number of free testing sites to make retesting, if necessary, widely available. Access to free testing sites helps limit the spread of COVID-19.
Even an additional antigen test after isolation may only be so helpful. Antigen tests, more than PCR tests, are prone to false negative results.
“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, an infectious disease specialist, epidemiologist, and associate professor of medicine at the Johns Hopkins University School of Medicine, 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,” added Dr. Rock.
To make things even more confusing: Let’s say you get a positive test result even after 10 days. That result 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.
Research has found that PCR tests can detect dead fragments of SARS-CoV-2, the virus that causes COVID-19, in your upper airway, even after you are no longer infectious.
The bottom line: Retest to confirm a negative COVID-19 test and previously had close contact with an infected person, frequently interact with others at school or work, or currently have COVID-19 symptoms.
Though the CDC guidelines can be hard to interpret, they’re the best course of action.
“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 one is available, you can use an antigen test at the end of your five-day isolation period. You do not need to retest more frequently than every three days after your initial five-day isolation, said Dr. Rock. Avoiding retesting too often helps avoid false test results.
No test (or CDC guideline) is reliable enough to tell you with 100% accuracy if you are still contagious, which is what retesting is all about.
“Being cleared for normal activities by your health care provider is the best course,” added Dr. Healton. The same goes for wearing a mask out in public. The most protective masks, N95 respirators, help shield you and others from SARS-CoV-2.
After testing positive for COVID-19, you may end your five-day isolation early if your symptoms subside and you are fever-free for 24 hours without using a fever reducer. Then, exercise caution by wearing a mask around others until 10 days after your first positive test or symptom.
You do not need to retest more than every three days after your initial five-day isolation. Retesting at the end of your isolation is an option, but the CDC does not require that you do so. In contrast, you may need to rest after 10 days if you had severe symptoms or have a weak immune system. Consult a healthcare provider to determine the best course of action.
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.