The HSE says industrial action will have a 'very disabling impact' on hospitals throughout the country today.
Over 2,100 medical scientists, who mainly work in public hospitals, are stopping routine lab services for 12 hours. Their industrial action began at 8am and will come to an end at 8 o'clock tonight.
Their pay dispute has led to inpatient and day-case procedures being cancelled.
Liam Woods, the HSE's director of acute operations, says there'll also be significant disruption to emergency care;
"The impact is really very disabling where testing isn't available services can't be provided and we face a real challenge with that. There will be I think some delay in emergency departments and we would be asking patients to first attend GPs where that's feasible for them."
The Union representing Medical Scientists, the Medical Laboratory Scientists Association (MLSA), said it has made every effort to avoid today’s disruption to patients and fellow healthcare workers, but has been left with no alternative.