The potential outcomes for affected staff would vary, he said.
"For example, where there is merging of activities in fewer locations existing staff might not choose to move, this could lead to redundancies."
Finance is one such service that is planned to be mostly in one location, said Mr Reynolds.
It was also possible warehousing and distribution staff would move to another place, he said.
Supply chain staff were likely to stay in the same place but have a change in employer, he said.
"It is important to note that the vast majority of benefits of the programme will not stem from reducing staff costs."
The programme aims to centralise the way district health boards buy hospital supplies, saving $500 million over a decade to be reinvested into frontline health services.
HBL chief executive Nigel Wilkinson said there was no single catalogue, ordering system or distribution system of the supplies and services DHBs buy.
"Every year DHBs spend about $1.3 billion buying goods and services, ranging from cotton-wool buds through to hospital beds."
Working together will be more efficient, he said.
"For example, perishable products will be redistributed between DHBs so stock can go to another hospital rather than going to waste. DHBs will also be able to buy goods and services off a single national catalogue, which will offer competitive prices."
Consulting with staff started in October and has not gone down well with some.
There were concerns that the supply department would be shut completely, said a Wairarapa health care worker, who did not want to be named because of employment concerns.
She said it had been handled secretively and there would definitely be redundancies.
"It seems to me they are closing the hospital little by little, questions need to be asked."
The department would not close, said Jill Stringer, communications manager for Wairarapa and Hutt Valley DHBs.
Public Service Association National Secretary Richard Wagstaff said while the shared services plan made sense financially, there was no doubt the changes would be unsettling and disruptive for staff involved.
"The biggest impact will be for staff in the smaller DHBs where jobs are being disestablished or decisions will have to be made around relocating or redundancy."
The union said 300 jobs across the country would be affected, with each DHB impacted differently.
The new system will be rolled out to DHBs in waves over the next couple of years, starting next year.