Covid test: When to take your lateral flow test - and do lateral flow tests expire?

As Omicron continues to spread in the UK, here’s when you should take a rapid Covid test – and why taking a lateral flow test before socialising matters.

Here's when you should aim to take your lateral flow test - and why it matters. (Inkdrop/Getty images via Canva Pro)
Here's when you should aim to take your lateral flow test - and why it matters. (Inkdrop/Getty images via Canva Pro)

With Scotland reporting 6,734 new positive coronavirus cases on Monday December 20 and Christmas fast approaching, people across the UK are being urged to get regularly tested for Covid-19.

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Lateral flow tests, designed for those not displaying Covid symptoms, are readily available from local collection sites, pharmacies and online at GOV.UK.

Expiry dates for certain brands of lateral flow home testing kits can be found on the test kit packaging, as shown.

But as experts and government officials warn that lateral flow tests may not register an accurate result due to the incredibly fast spread of the new Omicron variant, timing your lateral flow test properly is key.

So, when should you take your lateral flow test?

Here’s what you need to know.

When should I take a lateral flow test?

Due to the fast spreading nature of the Omicron variant, which has a doubling rate of anywhere between one to three days, health experts and government officials have urged people to take lateral flow tests just before socialising with others outside of their household.

In a Covid briefing on December 17, First Minister Nicola Sturgeon asked Scots to “stay at home much more than you normally would, and stay at home as much as you can” in the run up to Christmas.

But Ms Sturgeon also said: “I’m asking everyone to stay at home as much as possible, but if you are mixing with other people, please test yourself before you go - just before you go.

“If you are going out at night, don’t rely on a test from the morning – make sure you test yourself just before you go.”

The First Minister’s plea to Scots to test just before heading out to socialise was reinforced by minutes of the latest Scientific Advisory Group for Emergencies (SAGE) meeting released on Friday.

Stressing the increased risk posed by Omicron to all, with an almost three-fold risk of transmission in households with Omicron infections, SAGE scientists added:

“The negative predictive value of a negative test declines in a matter of hours, so a test should be conducted as close to a meeting or event as possible.

"Testing after attending a gathering or event is also important, with isolation of positive cases and contact tracing following.”

How long do lateral flow tests take?

Lateral flow tests, also known as rapid antigen tests, are often relied on for providing speedy results to confirm whether you have caught Covid-19.

With the tests themselves taking anywhere between two to 10 minutes to self-administer at home, results then take an extra 30 minutes to display.

A single line next to the ‘C’, which stands for ‘Control’, means your test is negative.

But if this line is joined by another, even a faint line, next to ‘T’ for ‘Test’, you have received a positive result.

Whether you test positive or negative for coronavirus, you should register your lateral flow test result online at:

Do lateral flow home testing kits expire?

With Omicron described as posing a “significant threat” to the UK’s recovery from the pandemic, it’s important to ensure that the lateral flow tests you are using have not expired as this could lead to an invalid result.

Instead, be sure to check your lateral flow home testing kit of seven tests for an expiry date.

Depending on the brand of tests delivered to your home for free from GOV.UK, this could be on the side or underside of the box.

Expiry dates for lateral flow home test kits range from months to years ahead.

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