Fire and Emergency crews worked to free the driver, who was trapped in their vehicle for over 30 minutes.
A police spokeswoman said the crash happened about 4pm. The vehicle left the road and ended up in a paddock beside State Highway 1, just north of Balclutha at Lovells flat.
The Serious Crash Unit would be investigating the cause of the crash, the spokeswoman said.
She was unable to provide the person's gender or age.
A duty manager at Dunedin Hospital said the patient's condition was still being assessed.