The Head of Starfleet Medical was a flag officer who oversaw the Medical branch of Starfleet.
In 2401, Admiral Beverly Crusher was given this post. In this role, she developed a fleet-wide transporter solution to remove the Borg DNA from Starfleet's young officers. Crusher also spearheaded technology that privately scanned for other irregularities, exposing the Changeling infiltrators in Starfleet. (PIC: "The Last Generation")