The Blue Murder actress, who is currently promoting the return of her BBC One sitcom Life Of Riley, reaches the milestone in July.
Speaking to GMTV about her forthcoming birthday, Quentin explained: "I'm thrilled, actually. I'm happy to be here - grateful to be well and fit. I'm just delighted."
The star added that she does not see any reason to feel ashamed about reaching 50, commenting: "We've all lost people before that. I feel really, really grateful - genuinely."
Life Of Riley returns at 7.30pm tonight on BBC One.
