Caster Semenya said "no human can stop me from running" after winning the 800m at the Doha Diamond League meet amid speculation over her future. It comes just two days after the South African, 28, lost a landmark caseagainst athletics' governing body. Semenya challenged IAAF rules designed to limit testosterone levels in female runners but the Court of Arbitration for Sport (Cas) rejected her appeal. "Actions speak louder than words," Semenya told BBC Sport. "When you are a great champion, you always deliver. "It's up to God. God has decided my life, God will end my life; God has decided my career, God will end my career. No man, or any other human, can stop me from running." The Doha meet was Semenya's final race before the IAAF's new rules come into force on 8 May. She added: "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. "I'm going to keep on doing what I do best - which is running." Under the new IAAF rules Semenya - and other athletes with differences of sexual development (DSD) - must either take medication in order to compete in track events from 400m to the mile, or change to another distance. On Thursday, Semenya posted a cryptic tweet that suggested she could quit athletics, including a quote which referred to knowing when to walk away. Asked by reporters whether she would take medication to allow her to run in the 800m, she replied: "Hell no." And she insisted she would be running in Doha again at the World Championships in September - though she did not know if that would be in the 800m or 5,000m races. "With a situation like this you can never tell the future but the only thing you know is that you will be running," she said. Victory in the opening Diamond League event of the season was her 30th in a row at 800m. The double Olympic champion showed no emotion as she crossed the finish line in the fastest time of the year and a meeting record of one minute 54.98 seconds, having dominated the race from the start. Burundi's Francine Niyonsaba finished second with the United States' Ajee Wilson third. Britain's Lynsey Sharp finished ninth. Sharp, 28, told BBC Sport she had received death threats as a result of previous comments she had made about Semenya's "advantage". "I've known Caster since 2008, it's something I've been familiar with over the past 11 years," she said. "No-one benefits from this situation - of course she doesn't benefit, but it's not me versus her, it's not us versus them. "I've had death threats. I've had threats against my family and that's not a position I want to be in. It's really unfortunate the way it's played out. "By no means am I over the moon about this, it's just been a long 11 years for everyone." Semenya can appeal against the Cas ruling to the Swiss Tribunal Courts within 30 days of the ruling.