Police are appealing for witnesses to determine the circumstances of the fall, which happened at around 10.15am on the B6113 Greetland Road, near Cut Edge Farm on Sunday.
The victim, 52, was cycling with a man when she fell.
A West Yorkshire Police spokesperson said: "It is believed she fell from her bike while the man was ahead and out of view, having possibly suffered a medical episode.
"The woman was taken to Leeds General Infirmary where she is stable with serious but none life threatening injuries.
"Officers would like to speak to anyone in the area at the time who saw the woman fall, the man and woman cycling, or who has any information about the incident."
Anyone who has assist is asked to contact PC Julian Ingham on 101 referencing log 579 of April 6.