US TV
ABC/'Grey's Anatomy'
The 29-year-old, who scored two box office hits with Knocked Up and 27 Dresses, is reportedly disillusioned with the long working hours on the ABC medical drama.
An insider said: "She's working really long hours and is ready to move on. She's a smart one.
"She saw what can happen with someone like Jennifer Aniston, who was crazy successful on TV, but can't seem to carry a film, and she tested the waters early."
The insider added that Heigl's Grey's Anatomy contract could mean she is locked into her role as Dr. Isobel Stevens for the foreseeable future.
Heigl previously denied reports that she would walk out on the show.
More: Katherine Heigl, US TV
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