Sanders career peaked in 2007 when she won the 400 metres at the 2007 European Indoor Championships (breaking the British Indoor record), and ran a personal best to win the silver medal at the 2007 World Championships behind compatriot Christine Ohuruogu. In the 4×400 metres relay, she won a bronze medal at the 2008 Beijing Olympics (retroactively awarded in 2017) and a gold medal at the 2012 World Indoor Championships. She also won four World Championship relay bronzes. After two years of struggling with injury, she announced her retirement from athletics in October 2014.