The competitive future of Olympic champion Caster Semenya is in doubt after she said she would not take medication to lower her testosterone levels to comply with new rules for the 800 metres.

Semenya raised her fist at the start of her 800 metres at the opening Diamond League meeting of the season in Doha, Qatar, on Friday and flew round the track to claim a typically dominant victory.

After the race, she game an emphatic answer as to whether she would submit to new testosterone regulations in track and field and take hormone-reducing medication, as required by the International Association of Athletics Federation (IAAF) via a rule set to come into effect on May 8.

“Hell no,” the three-time World Champion said.

Semenya’s win in Doha, with a meet record of one minute, 54.98 seconds, came two days after her defeat in a landmark court case against track and field’s governing body.

It was the South African star’s fourth-fastest time ever, and her nearest challenger – Olympic silver medallist Francine Niyonsaba, who two weeks ago confirmed she had the same hyperandrogenism as her rival and would also now be forced to take medication – was nearly three seconds and about 20 meters behind her.

It was Semenya’s first 800 metre race this year and first since losing her case in the Court of Arbitration for Sport (CAS) against the IAAF’s ruling, which will require female athletes with high levels of natural testosterone to medically lower them to be eligible to compete in events ranging from 400 metres to the mile (1.61 kilometres).

“Actions speak louder than words,” Semenya told the BBC. “When you are a great champion, you always deliver.”

But Semenya’s four-year dominance over two laps – Friday’s win was her 30th straight in the 800 metres, continuing a run that started in late 2015 – may now be at an end.

To compete, she must now medically limit her testosterone level to under five nmol/L, which is double the normal female range of below two nmol/L but still lower than that naturally produced in her body.

She failed to overturn those rules in her appeal to the Court of Arbitration for Sport.

Despite the CAS ruling, Semenya was emphatic when she told reporters after Friday’s race that she wouldn’t take the medication.

The IAAF’s rules were called sexist, racist, unethical, and based on bad science, but the governing body dug its heels in.

“That’s an illegal method,” she said.

But Semenya also didn’t give a clear idea of what she would do next.

Semenya could compete in longer, or shorter, distances not affected by the rule change.

She claimed the 5000 metres title at the South African Athletics Championships last week, an event not covered by the IAAF regulations, but in a modest time of 16:05.97, well below the qualifying standard for the world championships, 15:22.00.

“I’m a crazy athlete, I switch events like hell, but yeah, 800 metres is my calling, I believe in it, and that’s what I want to do,” she said.

I will switch races when I want to – no man can tell me what to do.

“I’m here for a purpose: if I want to switch events I switch them, but if someone wants me to switch them, that’s their own problem, not mine.

“I’m a power athlete: I can run from 100 metres to five kilometres, so I can run any race I want.”

After the race in Doha, Semenya told the BBC that she still had a long career ahead of her in athletics.

“God has decided my career, God will end my career,” she said in the BBC interview.

“No man, or any other human, can stop me from running. How am I going to retire when I’m 28? I still feel young, energetic. I still have 10 years or more in athletics.

“It doesn’t matter how I’m going to do it. What matters is I’ll still be here. I am never going anywhere.”

Semenya’s comments may foreshadow an appeal against the CAS ruling, aimed first at allowing Semenya to defend her 800 title at the world championships – which will take place in Doha in September and October – while not taking the hormone-suppressing drugs.

But if she keeps her promise not to lower her testosterone, the likelihood was that Friday was the last time she would run competitively in the 800 metres.

After Semenya won in Doha, she was presented with a bunch of flowers that she then tossed into the crowd. She gave a thumbs-up to fans, flashed a brief smile, and walked off the track.

-ABC/agencies