Laboratory scientists who carry out Covid-19 testing have served notice of industrial action later this month in a row over pay.
Strike action is set to take place between 8am and 8pm on May 18, and further work stoppages are planned on May 24 and 25.
Three further days of action are planned for the following week on May 31, June 1 and June 2.
The Medical Laboratory Scientists Association said routine laboratory services will be withdrawn, which will affect hospital and GP services.
The medical scientists carry out critical testing of patient samples, including for coronavirus in public hospitals.
The MLSA said notice of industrial action on May 18 has been served in the long-running dispute over pay and career development issues.
It said talks convened by a public service agreement group broke down.
The union claims 20pc of posts are unfilled.
MLSA chairperson Kevin O’Boyle said medical scientists are highly frustrated and want their long-standing issues properly resolved by the HSE, Department of Health and Department of Public Expenditure and Reform.
“The latest failure by the HSE and Department of Health to put forward any proposal has added insult to injury,” he said.
He said the MLSA had withdrawn notice of strike action on March 30 in good faith, but the employer side offered nothing to address members’ issues.
“We regret the difficulties it will cause to an already over-burdened health service and to patients awaiting treatment, but there is huge frustration and burn-out among our members because the severe recruitment and retention problems in the sector have been ignored for years,” he said.
“Up to 20pc of approved medical scientist posts are unfilled in hospitals across the country. We have tried to avoid this action but have been left with no alternative.”
MLSA general secretary Terry Casey said the union’s door will remain open to any meaningful approach or solution from the employer.
Mr Casey said there is a significant national shortage of medical scientists across the public health service.
“This is in no small part due to inferior pay and conditions, poor career structure and limited promotional opportunities,” he said. “This must be addressed so that the Irish health service can have the clinical diagnostic laboratory service it requires.”
The disputes dates to 2022 and involves a claim for pay parity with scientists in biochemistry laboratories.
“Medical scientists carry out identical work, with the same responsibilities, and yet are paid on average 8pc less, with fewer promotional and career development opportunities and less support for training and education,” said Mr Casey.
“Public sector health workers from nurses, consultants to lab aides have secured significant pay increases in recent years.
"For medical scientists this, combined with the advancing role of laboratory diagnostics, increased responsibility, increased workloads and the long-standing challenges in recruitment and retention mean these employment issues need to be addressed.”