Johnson, who was diagnosed with Type I diabetes when he was 11 years old, had been taking part in drills on an auxiliary practice field behind the main diamond. He was driven off the field by assistant trainer Brian Ebel and clubhouse manager Freddy Tyler.
Tyler drove while Ebel sat next to Johnson, who laid with his legs dangling over the edge of the cart. Five minutes later, as Johnson lay on the cart in a breezeway between the team's clubhouse and the batting cages, a team of emergency medical technicians arrived on the scene.
After sitting up, Johnson, 29, was seen swallowing something out of a white container, likely an item containing sugar. Ten minutes later, he got up off the cart under his own power and walked into the clubhouse. Johnson did not go to the hospital and later he left on his own.
The Baltimore Sun reported Thursday that Johnson has Type I diabetes, and has similar reactions to low blood sugar about once or twice a year.
Orioles team physician Dr. William Goldiner, one of two doctors who tended to Johnson at the scene, said paramedics were called in case glucose had to be administered intravenously.
Initially, the situation appeared similar to the one that took place at Fort Lauderdale Stadium on Sunday, when fellow pitcher Steve Bechler was carted off the field and rushed to the hospital. Bechler spent all Sunday night in intensive care, and he died of multisystem organ failure Monday morning.
Because of the Bechler tragedy, Johnson's incident unfolded in a much more tense atmosphere than it otherwise would have.
"Everybody's obviously a little hypersensitive right now," said Orioles Manager Mike Hargrove. "You have those things with Jason, but it still scared the hell out of everybody."
A private memorial service to honor Bechler was held late Wednesday.
After the service, team owner Peter Angelos called for a ban on ephedrine. He said last year, when he was a member of the owners' labor negotiating team, the union did not want the ban.
"The union rejected our position and would not agree to include those on the basis that if they are legal, there should be no prohibition imposed by the clubs," Angelos told the Washington Post. "And as a consequence, without that being included in the agreement, we simply cannot prohibit them. Hopefully, with this terrible tragedy, a reassessment of the union position will come."
Already at the complex for the memorial, members of Bechler's family stood in the breezeway and watched as the emergency medical personnel administered to Johnson. Bechler's brother, Mike, walked up and stood right near Johnson as the incident unfolded. The family left only minutes later without commenting.
Orioles spokesman Bill Stetka said he didn't think Johnson had eaten and that Johnson's schedule had been thrown off because the team started workouts late.
Johnson, who has been wearing an insulin pump to regulate his blood sugar since the 2001 season, has had similar on-field incidents before. No serious problems have resulted from them.
The 6-6 Johnson went 5-14 last season.
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