In 2013 she became junior world champion in the team pursuit before graduating to the Great Britain Cycling Team Olympic Podium Programme in 2016.
That year also brought success for Kay as she won gold and bronze in the team pursuit and omnium at the UEC Under-23 European Track Championships in Italy before winning senior European honours at the UEC European Track Championships later that year, earning bronze and silver in the team pursuit and Madison.
European honours then earned a call-up to the Great Britain Cycling Team for the opening round of the 2016/17 UCI Track Cycling World Cup in Glasgow, with Kay winning double gold in both the omnium and the team pursuit.
She followed up on that with silver in the omnium a week later at the second round of the world cup in the Netherlands - results which saw her selected for her first UCI Track Cycling World Championships in Hong Kong in April 2017, where she was part of the British squad that finished fifth in the team pursuit.
|UCI Track Cycling World Cup, Apeldoorn (Netherlands)||Omnium||Silver|
|UCI Track Cycling World Cup, Glasgow (UK)||Omnium||Gold|
|UCI Track Cycling World Cup, Glasgow (UK)||Team pursuit||Gold|
|UEC European Track Championships, Paris (France)||Team pursuit||Bronze|
|UEC European Track Championships, Paris (France)||Madison||Silver|
|UEC Under-23 European Track Championships, Montichiari (Italy)||Team pursuit||Gold|
|UEC Under-23 European Track Championships, Montichiari (Italy)||Omnium||Bronze|
|UCI Junior Track World Championships, Glasgow (UK)||Team pursuit||Gold|
|UCI Junior Track World Championships, Glasgow (UK)||Omnium||Bronze|