If by dying you mean regenerating, he's regenerated in nine episodes:
- First Doctor - "The Tenth Planet"
- Second Doctor - "The War Games"
- Third Doctor - "Planet of the Spiders"
- Fourth Doctor - "Logopolis"
- Fifth Doctor - "The Caves of Androzani"
- Sixth Doctor - Time and the Rani
- Seventh Doctor - Doctor Who - the movie
- Ninth Doctor - Parting of the Ways
- Tenth Doctor - "The End of Time"
The Eighth Doctor's regeneration hasn't been shown on screen. The Tenth Doctor was shot by a Dalek in "The Stolen Earth" and attempted to regenerate but aborted it.
If by dying you meant death, this hasn't happened and we can't predict the future.