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COVID tests - PCR vs lateral flow

Dr Karen Martin
Reviewed by Dr Karen MartinReviewed on 19.10.2023 | 3 minutes read

Polymerase chain reaction (PCR) tests have been used since the start of the pandemic to test for the presence of the virus and alert scientists to any new variants. A PCR test needs to be sent off to a laboratory, and results can take one to three days to return.

Rapid lateral flow tests came in a bit later in the pandemic, and can be done at home, with the result quickly available within minutes and they resemble a pregnancy test.

Generally speaking, the lateral flow test is useful for those without symptoms and the PCR test is for those with symptoms. Anecdotally, the PCR test may show positive a few days prior to the lateral flow test.

How have rules changed?

The US government previously had a policy to test those with symptoms and legally request they isolate for a certain number of days. Testing was used to confirm infection and to release from isolation early if negative.

However, the government’s current strategy is now to learn to live with COVID-19, and has significantly scaled back testing requirements, preferring instead that the public takes responsibility to isolate themselves if they think they have caught COVID-19, but now without any legal requirement to do so.

Taking a lateral flow test with no symptoms

Lateral flow tests are a highly reliable way of testing those without symptoms. You may order free at-home tests by visiting

Rapid lateral flow tests are also available to buy from pharmacies and other retailers, and people may wish to use these for regular testing if they are mixing outside their household and want the reassurance of knowing they remain COVID free.

So if I can’t get a test, how do I know I’ve got COVID?

From the start of the pandemic, there have been three typical COVID symptoms - a new persistent cough, fever and change to your sense of taste or smell – although multiple other symptoms are linked to this infection.

With most people being fully vaccinated now, and new virus variants emerging, these symptoms are no longer typical of a COVID infection, and the medical authorities have added nine more COVID symptoms: shortness of breath, feeling tired and exhausted, an aching body, a headache, a sore throat, a blocked or runny nose, loss of appetite, diarrhea and feeling nauseous or being sick.

With these symptoms, you may feel more like curling up under the duvet than meeting friends or going to work, but without access to testing, these may be an indication that you should avoid others, especially those who are vulnerable.

What about self-isolation?

With the new rule changes, there is no longer a legal requirement to isolate if you’ve tested positive for COVID or have the symptoms and so you don’t need to prove you have a negative lateral flow test after a certain number of days in order to end your isolation.

However, the US government continues to encourage people to act responsibly to prevent spread of any infection, so if you suspect or know you have COVID, it's advised that you stay at home for at least 5 days and avoid contact with others where possible.

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This article has been written by UK-based doctors and pharmacists, so some advice may not apply to US users and some suggested treatments may not be available. For more information, please see our T&Cs.
Dr Karen Martin
Reviewed by Dr Karen Martin
Reviewed on 19.10.2023
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