Police were called at about 12.30pm on Tuesday to Lancaster Road (A683) in Caton following reports of an accident.
A 33-year-old man riding a Suzuki motorbike westbound had come off his vehicle after attempting to overtake a Volkswagen Transporter.
The Air Ambulance was called and the man, from Lancaster, was taken to Royal Preston Hospital for treatment to a punctured lung, fractured shoulder and further fractures to his collar bone and back.
The driver of the Volkswagen, a 45-year-old man from Heysham, was uninjured.
Police are appealing for information following the incident.
Sgt Rob Gomery, of Lancashire Police, said: “We are appealing for witnesses following a road traffic collision in Caton.
“A 33-year-old man fell from his motorbike on Lancaster Road and we want to establish the exact circumstances.
“If you saw either the motorbike or van prior to the collision, or witnessed the incident, call police immediately.”
Anyone with information can call police on 101 quoting log reference 481 of February 14.