Police said the man was struck by a small, dark car in the town's Moor Road just after 19:00 on Wednesday.
He is being treated for head injuries at the Queen Elizabeth University hospital in Glasgow. His condition has been described as serious but stable.
Police want to trace the driver of the car and have appealed for anyone who witnessed the crash to contact them.
A 26-year-old man has been seriously injured in a hit-and-run incident in Milngavie, East Dunbartonshire.