Dialysis is carried out on those who have had kidney failure, and can take up to six hours.
Mrs Marsters Kupa is among a group of dialysis patients who have complained to Auckland's district health boards about patients reportedly being delayed up to three hours, not being picked up from hospital, and drivers refusing to assist elderly and disabled people.
Mrs Marsters Kupa, who is blind, said she had been taken to the wrong house three times and had been left to "fend for myself" when dropped off at the hospital.
She has vowed never to travel by a Co-op taxi again - despite being entitled to the service - and yesterday paid her own way in a North Harbour Taxi.
That company was contracted with the patients for more than a decade.
It has been almost a month since Co-op took up the contract with healthAlliance, which looks after such services on behalf of Auckland DHBs.
A spokesman for Auckland Co-op did not want to comment to the media.
The healthAlliance chief executive, Mike Schubert, said it was investigating a number of concerns raised by patients.