Barry McHugh has been taken to hospital following a nasty fall as he attempted to mount Notnow Seamus in the parade ring before a mile-and-a-half maiden at Thirsk.
The jockey was treated at the scene before being accompanied by a racecourse doctor to hospital for precautionary checks.
"Barry has gone to the James Cook Hospital in Middlesbrough to be checked out," said clerk of the course James Sanderson.
"He had a bad fall in the parade ring as he was getting on his mount.
"He landed quite heavily and on the back of his head. Hopefully, it's nothing more serious than concussion.
"He was conscious, but certainly dazed.
"He's gone to the James Cook with one of the doctors in one of the ambulances where he will obviously be checked out thoroughly."