Health chiefs in north Wales have responded to union concerns that workers will be forced to retire at 65.
The Unison union says pensionable staff are being sent letters, giving them six months notice, from the Betsi Cadwaladr University (BCU) Health Board.
A board spokesman said it had a duty to write to staff before their normal retirement date, giving them the right to ask "not to be retired".
The union said "a lot of experienced staff" were being lost.
It is unclear how many people might be coming up to retirement age, but the health board website says it employs around 18,000 staff and has a budget of about £1.1bn.
'Judged on merit'
Dave Griffiths, branch manager for Unison at BCU, said staff had always had the opportunity to work past 65, although each application to do so was judged on merit.
He said people who have carried on working past 65 had now been sent letters giving them six months notice of the end of their contracts.
A small number of people had appealed, but none has so far been successful, with more appeals in the pipeline.
"We are losing a lot of experienced people here," he said.
"They're very loyal to the new health board and the areas they work, and particularly loyal to the patients they serve, and to giving them the best possible care, even backroom staff.
"They are upset at what's happening," he added.
A spokesman for the board said it was writing to some people who have continued to work beyond 65, to clarify their position.
He said that if they did so they should get a fixed extension on their contract, generally of one year, to be renewed at the end of the extension, when a further extension could be granted.
He added: "We haven't always been on the ball as people approach 65, and some people have slipped through the scheme and are now being written to."
When asked whether the move was financially motivated he said: "It's about efficiency and good practice, but the financial context will always inform our decisions.
"In the current climate, financial considerations are at the back of our mind in every decision we take," he added.