Another 50 were wounded in the attack in which gunmen disguised as doctors stormed the hospital and exchanged fire with security forces for several hours.
All four attackers were also killed during the six-hour gun battle, officials said.
The assault on the Sardar Mohammad Daud Khan Hospital began when a suicide bomber blew himself up at the rear entrance to the building.
The other three attackers, carrying automatic weapons and grenades, then entered the complex. LINK