Today's nursing strike will mean many non-urgent or routine hospital appointments will have been postponed.
Health chiefs are asking residents to check their local health board, in Monmouthshire's case the Anueran Bevan University Health Baord, as appointments will be rescheduled.
The Royal College of Nursing announced its members will go on strike on December 15 and again on December 20, with further action confirmed this month by the GMB union.
During the industrial action, NHS services are likely to resemble those usually provided on public holidays. People in need of urgent assistance or with life-threatening conditions are advised to attend emergency departments or contact the emergency services as they would on any other day.
As part of discussions ahead of industrial action, NHS employers and trade unions mutually agree exemptions from strike action, or ‘derogations’, to ensure the continuity of urgent or life-threatening care during any strikes.
Non-urgent or routine appointments are likely to be postponed. Health boards will inform patients and aim to reschedule new appointments as soon as possible.
The Welsh Government has advised people with non-life-threatening conditions to use the NHS Wales 111 digital service in the first instance. Local health board websites will provide the latest information on the strikes’ impact on local services.
Eluned Morgan, the Minister for Health and Social Services, said: “We believe all public sector workers should be fairly rewarded for the important work they do.
“The strikes which begins today will inevitably have a significant impact on NHS services. But we recognise the strength of feeling among staff, which the difficult decision to vote for industrial action reflects.
“While we were unable to avert this week’s industrial action, all partners have agreed to keep talking and continue to work together. We will work continue to bring together trade unions, employers and government to deliver the best possible outcomes for workers within the funding we have available.”