Frontline NHS, social care, hospice and special school staff will be asked to take a lateral flow test (LFT)every day by the Welsh government.
The stepping up of guidance on routine testing comes in response to the expected Omicron wave.
Tests should be taken “in good time” before the start of a shift, Health Minister Eluned Morgan said.
It comes as the UK records its highest Covid case figures for a third successive day.
Mark Drakeford has announced new restrictions on businesses from 27 December, including the closure of nightclubs.
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In a statement, Ms Morgan said staff eligible for routine asymptomatic testing will be “strongly encouraged to take a LFT every day before they attend work”.
She added: “They should take the test at home, using the LFTs provided by their employer, in good time before the start of their shift, to allow that shift to be covered by alternative staff member, if the test is positive.”
She said daily testing was more likely to identify those who were more infectious.
“We are engaging with our partners across the relevant sectors to support the implementation of this change in guidance so operational changes can be made as soon as possible,” she added.
Frontline health and social care staff were previously asked to take two weekly tests.
It later emerged that some hospitals did not implement the policy, unveiled in December 2020, until March this year.
Deputy chief medical officer Chris Jones later said he did not think twice-weekly testing was “particularly important in the whole scheme of things“.
He said they were a “small part” of a “huge range” of infection control measures.
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