The incident occurred 45 seconds into the third period of Toronto's 4-2 win on Wednesday night. Lupul received a two-minute minor penalty for an illegal check when he hit Hedman in the head after the defenceman passed the puck in the neutral zone.
It was just Lupul's second game back after missing 25 contests with a broken arm. He scored three goals in those two games.
Lupul will forfeit US$45,945.94 in salary. He has no history of supplemental discipline in his nine-year career.
"I've got to see the replay, but by no means did I go after him and try and hit him in the head," Lupul said after the game.
The league ruled that Lupul "recklessly targeted" Hedman's head.
The six-foot-six Swede briefly left the game but returned and suffered no apparent injury.
Lupul has been playing on a line with Nazem Kadi and Nikola Kulemin. The trio combined for six points in the victory over Tampa.
Lupul will miss games against Buffalo on Thursday and Boston on Saturday.