Ortiz was hospitalized for two days last week to undergo extensive heart testing after he complained of palpitations. He was released Thursday from Massachusetts General Hospital and wore a heart monitor over the weekend.
"I'm just happy to be out of the house," Ortiz said before batting practice Tuesday. "Everything's fine, that's the most important thing."
Ortiz was in the lineup as the designated hitter, batting third, for Tuesday night's game against the Chicago White Sox.
"The ongoing monitoring of David Ortiz has not identified any further problem," team medical director Dr. Thomas Gill said in a prepared statement.
"As a result, the team of consultants caring for David has met and decided to allow him to return to play today," Gill said. "The Red Sox medical staff will continue to monitor David on a daily basis."
Ortiz said he's no longer wearing a heart monitor or taking any medication -- just "rice and beans."
"I'm happy to be back, to be able to play. It's a little crazy watching the game on TV," he said.
Big Papi says he's not worried about being rusty after a week off. When he was pulled from the lineup last Monday before a game in Oakland, Ortiz led the majors with 47 homers.
But Philadelphia's Ryan Howard has taken the lead, hitting his 53rd homer Monday.
"I'm going to go out and do what I can do," he said, politely dismissing a question of whether he'll catch Howard. "I don't go out there thinking about hitting homers."
Information from The Associated Press was used in this report.