Dr Brian Keighley, chairman of the British Medical Association (BMA) in Scotland, also said much of the detail about plans to transform care "remains undetermined".
He was speaking as the BMA published a new paper making a number of recommendations on how health and social care could be better integrated.
It is calling for an "honest debate about what resources are required and available to provide services in hospitals and the community".
New legislation which should see the two sectors work together more closely was approved last month.
Health Secretary Alex Neil said then that the changes in the Public Bodies (Joint Working) (Scotland) Bill should ensure "joined up seamless health and social care provision that will improve people's lives".
But the BMA paper said that a number of workforce issues must be addressed, with GPs' workload already at "saturation point" and hospital doctors also under increasing pressure.
The BMA said: "Additional medical posts must be developed and properly resourced to meet changing demand and to deliver more care in the community."
Dr Keighley said a lack of community support often created barriers that prevented frail and elderly people from returning home after a hospital stay.
He added: "While the plans to integrate services are welcomed by doctors, they are likely to require additional resources in order to increase capacity in the community and in primary care."