Carter was on a flight Tuesday from Atlanta to Cleveland when he became ill. Rescue crews rushed him to the hospital after the plane landed.
In a statement released by the hospital Wednesday night, "President Carter thanks all those who have expressed concern and sent greetings to him."
Police cars, television crews, ambulances and SUVs were lined up outside the hospital Thursday morning to watch Carter leave.
He waved to the cameras as he walked out of the emergency room and again from a vehicle as the motorcade passed the media.
His brief illness interrupted his tour to promote his new book, "White House Diary."
Planned book-signings in Ohio and North Carolina were called off Tuesday. His publisher also canceled scheduled events in Washington on Wednesday, including one at the Smithsonian Institution.
Carter, who was a former peanut farmer, was elected to the White House in 1976. He has spent in his recent years pursuing peace and human rights, efforts that won him the Nobel Peace Prize in 2002.
In his new book, he talks about how he pursued an overly aggressive agenda as president that may have confused voters and alienated lawmakers.
The Associated Press contributed to this report.
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