I’m a doctor and here’s how some FRUIT can give false positive lateral flow tests

LATERAL flow tests have become the norm in the UK due to the spread of coronavirus infections.

Long periods of time in isolation has meant that some people have gotten creative with their tests – including testing them with fruit juice.

Social media users were left shocked when one TikTok user cut open a kiwi fruit and swabbed it, using the juice in the pipet.

They then put the juice into the test – with two positive lines coming up.

One doctor has explained why this is actually a false positive and doesn't mean that your delicious kiwi does in fact have Covid-19.

Taking to the platform to debunk the 'my kiwi has Covid' myth, Dr Karan Rajan revealed how the lateral flow tests actually work.

He explained: "This is your daily reminder that that you're not a kiwi, unless you're from New Zealand.

"Inside your lateral flow test there is a strip known as the conjugation pad.

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"This is where antibodies are attached to gold nano particles and for the test to work properly it needs stable electrostatic interaction between the gold nano particles and antibodies.

"These biological components are very pH sensitive.

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"If you change the pH by adding something acidic like a kiwi fruit, this can completely change the charge on the antibody and corrupt the test giving you a false positive."

Other doctors have previously had to explained why water and fizzy drinks will also mean you get a positive lateral flow test.

NHS doctor and nutritionist Dr Joshua Wolrich, explained that the solution you put the swab into after it's been in your nose/throat is what's known as a buffer solution.

He explained: "It has a controlled pH that allows the test to work accurately.

"Pouring any other sort of liquid without controlled pH (tap water, coke, etc) on the test is completely and utterly pointless.

"If it comes up with two lines after that, it's not proof that the test has always been pointless or whatever nonsense the anti-vaxxers are claiming.

"It's simply a visual representation that medical tests are only valid when the instructions are followed and the pH of your solution is giving you a meaningless result."


When it comes to detecting the bug in adults, previous studies have shown that the tests are over 80 per cent effective at detecting any levels of the virus.

The paper, published in Clinical Epidemiology found that the test detected 90 per cent of infections when people were most infectious.

The UK Health Security Agency also previously found that lateral flow tests are as effective at detecting Omicron than other variants before it.

If you test positive then you must isolate in order to stop the spread of the bug, but if you haven't got symptoms you might be worried about getting a false positive.

People having been taking lateral flows now for well over a year due to the pandemic and it's important that you always read the instructions that come with tests and many are manufactured in different places, so you might have to do them differently.

One of the main instructions on most packs though is that you should wait 30 minutes after eating or drinking to take the test.

This is due to the fact that some foods and drinks, such as water and fizzy pop, can interfere with the test.

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