The actress played Bev Unwin from 2003 until her departure from the Street in December 2006. Blake will play Sheila Barlett in an episode of the BBC drama due to air later this year.
Dr Kevin's (Simon Rivers) suspicions are raised when he sees that Sheila has bruises on his body. His assumption that she is a domestic violence victim leads to the discovery that her husband is responsible for the injuries, however, it is not in the way Kevin believes.
Blake's guest appearance at Mill Health Centre will be broadcast in the autumn.
The 61-year-old actress, who went on to appear in West End musical Wicked after leaving Coronation Street, featured on the BBC's Let's Dance For Sport Relief earlier this year.
Doctors returns to BBC One on Monday at 1.45pm.
> Read our exclusive interview with Doctors series producer Peter Lloyd
> More Doctors news and spoilers