The changes, brought about by financial and staffing strains, have resulted in residents who fall ill from between 10pm and 8am having to either call 111 or use an after-hours telephone triage service.
Cromwell GP Greg White has warned that system could put patients at risk.
SDHB strategy, primary and community executive director Lisa Gestro said there had been no reduction in service.
''You can absolutely get a doctor at any time, day or night, in that area. We perhaps needed to be a bit careful about our comms.''
Some people regarded the changes as a downgrade, whereas it was intended to be ''transitional'', Mrs Gestro said.
''If you need care during the day, you ring your GP as you always did, and if need help after hours, you call a nationally recognised telehealth service.''
SDHB chief executive Chris Fleming noted the number of after-hours medical emergencies in Central Otago were extremely small.
Mrs Gestro said there had been some calls, and the SDHB was closely monitoring the way the system was progressing.
