Elmir, Australia's flyweight champion, had tested positive for a banned diuretic at the championships in Hobart.
Furosemide and Amiloride - prohibited in-competition and out-of-competition substances - were present in her sample, the Australian Sports Anti-Doping Agency said on Wednesday.
She was notified of her suspension shortly after arriving in China last week to compete at the women's world championships in Qinhuangdao, her manager Alex Belperio told Reuters.
"It's a provisional ban, that's all we know," Belperio said. "We appealed to have the ban lifted so she could compete in China, but the appeal was unsuccessful.
"It's been a bit of an emotional roller-coaster for her as you can imagine.
"We need to find out more information to determine what actions we can take in relation to this ban."
The 30-year-old Elmir was due to compete in the women's flyweight (48-51kg) category at the world championships, where a first-place finish among the Oceania boxers would have booked her ticket to London, where women's boxing will debut.
She was regarded as one of Australia's strongest medal hopes in the sport.
Boxing Australia had consulted ASADA before suspending Elmir on May 7, the anti-doping watchdog said.
"The athlete appealed to the Court of Arbitration for Sport against the provisional suspension; CAS heard the appeal on 9 May 2012," it said.
"The decision to uphold the provisional suspension was handed down on 10 May 2012."
The full CAS hearing was yet to take place, the ASADA added.
Boxing Australia declined to comment, but officials were distressed by the timing of the decision.
"You have to wonder whether tortoises could have handed it down any quicker," said Tony Whelan from Boxing ACT in Canberra.
"We would have hoped to have replaced her with the silver medallist, but of course there was no time to fly her over," Whelan said, referring to Kelly McGrath who was defeated by Elmir for the Australian title in Hobart.
Kristy Harris, who was hastily slotted into the draw to replace Elmir at the world championships, was beaten in the first round on Saturday.
Elmir's coach Garry Hamilton said the boxer had taken a tablet before the national titles to treat "swollen ankles" on a long-haul flight.
"She's taken the substance, that's not denied, but she wasn't aware it was going to do what it did, it wasn't done to help her with her boxing," Hamilton told local media.
"I really believe she's taken it for this medical reason, and only for this medical reason."