Dawn Chalmers (30), who lives in Nelson, has been banned until May 16 by the Sports Tribunal after admitting she took the drug furosemide before the national champs in Rotorua in October last year.
In its decision, the tribunal said it regarded this case as more serious than others it had dealt with concerning prohibited substances being mistakenly prescribed because of Chalmers' explicit knowledge that there was an issue about furosemide and her failure to clarify her position.
She was suspended immediately after the championships, and the penalty imposed by the tribunal after its hearing last month was for another three months, meaning she is banned from boxing until the middle of May.
The tribunal accepted she had not taken the medication to improve her sporting performance.
Furosemide can be used to reduce weight and help boxers reach weight divisions.
Chalmers said she was suffering from a stomach cramp immediately before the championships and took the drug to help the condition.
Her doctor had advised her not to take it "close to" or "around competition", and Chalmers said she was wrong to take the drug.
"It was just a mix-up, really. But I've learnt my lesson the hard way. I get tested really frequently, four or five times a year, but because it was not for an injury I didn't really think properly," she said.
"My doctor was nearly in tears but it was not his fault. I should have known better."
Chalmers, who was trained in Dunedin by Eldon Clifton, said the ban would not be too much of a hindrance as she could still train.
The only bout she could have fought if she had not been banned was at the Otago Championships, but as it would have been difficult to find an opponent at the champs, a fight probably would not have eventuated.
Chalmers is busy training for the Olympic qualifying tournament in Barbados in September.
She is trying to put on weight for the middleweight category, between 69-75kg.
There are only three weight divisions when women's boxing debuts at the London Games in 2012, and only 10 boxers in each division.
