NHS Greater Glasgow and Clyde is scrapping the on-call clinical team which transfers seriously ill patients from wards to theatre, intensive care or other hospitals.
The team, which is available 24-hours a day, consists of a junior doctor and at least two highly trained nurses, who stabilise the patient and ensure they are transferred safely.
But Glasgow's medical training committee has withdrawn the accreditation for junior doctors to fulfil the role.
The health board say all patients requiring transfer will now be accompanied by a doctor and say it is planning to increase staffing levels to cope with the changes.
However, union leaders have expressed concern about the changes and fear the role with fall to inexperienced staff.
Matt McGlaughlin, of Unison Glasgow, said: "We are extremely concerned that patient care and staff safety could be put at risk by this decision."
But a spokeswoman for NHSGGC said: "We are no longer operating a separate on-call rota for the transfer of critically ill patients.
"Instead, we are now operating the system that is in use across the whole of the UK for transferring patients from one ICU to another. This involves the referring hospital supplying a suitably qualified doctor and nurse to accompany the patient to the receiving hospital.
"We have planned for this new way of working for some months.
"Actions taken include increasing critical care nurse staffing across the board in order both to minimise the need for transfers, and to provide the necessary expertise should a transfer be required."
She added: "We have also ensured that appropriately trained doctors are available to support these arrangements as well as investing in additional equipment and support for staff.
"We are committed to patient safety and can state categorically that all patients will be transferred in an appropriate and safe way."