"I feel fine," Reno, 63, said as she left Strong Memorial Hospital. "Rochester takes very good care of its people. I feel good."
Reno, who has Parkinson's disease, said she didn't think the fainting spell would hurt her campaign for Florida governor.
She said it had happened before, and besides, "George Bush fainted," she said referring to the president's recent fainting spell after a pretzel became stuck in his throat.
"I got hot about when I started speaking because it was hot up on that corner of the stage," Reno said. "I just got progressively hotter, and I then said I had to sit down and I exited gracefully or ungracefully. I don't know how."
Reno had been speaking for about 45 minutes at the University of Rochester on Wednesday night when she fainted. She told the audience, "You're going to have to excuse me for a minute. I'm going to have to sit down." She then collapsed.
Before the speech, she attended a fund-raiser and a press conference.
Reno said Thursday that doctors told her "it seems to be a simple thing."
She asked her doctors not to discuss her health with the media, and the hospital planned to release only a statement later Thursday. Reno planned to return to Florida later in the day.
Reno, a Miami native, was diagnosed with Parkinson's disease in 1995 but has said it would not prevent her from serving as governor.
Joe Geller, former chairman of the Miami-Dade Democratic Party, suspected the former prosecutor's hectic schedule played a part in the fainting.
"Just from personal knowledge, I wouldn't be surprised if it was just exhaustion. Janet keeps a very busy schedule," he said.
Reno was the first female attorney general in U.S. history, serving during the Clinton administration. She is one of five Democrats attempting to unseat Gov. Jeb Bush.
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