Born near
Mount Elgon, Chepkwemoi had her first success at national level in 2010. After placing top ten in the Kenyan junior cross country race, she won the Kenyan junior title in the 1500 m. The 16-year-old Chepkwemoi took the bronze medal at the
2010 World Junior Championships in Athletics with a personal best of 4:11.04 minutes. This made her the second fastest
youth athlete in the world that year, behind only world junior champion
Tizita Bogale. She was chosen for the junior team at the
2011 IAAF World Cross Country Championships, where she placed sixth and helped Kenya to the team silver medals. On the track, she was beaten by
Annet Negesa of Uganda over 1500 m at the
2011 African Junior Athletics Championships, finishing a close second. She also set a personal best of 4:07.63 minutes that season while winning at the
Meeting Voor Mon meeting in the Netherlands. Her
IAAF Diamond League debut came that May and she set a
3000 metres best of 8:56.52 minutes to come tenth at the
Doha Diamond League meet. She returned to the world stage at the
2012 World Junior Championships in Athletics, but despite being older finished one place lower than in her previous appearance – teammate Kipyegon won the title and Ethiopia's
Senbere Teferi edged her out of third place. She set indoor bests of 4:23.76 and 9:02.28 minutes for the 1500 m and 3000 m at the start of 2013, but missed the rest of the season and also the whole of the 2014 season. ==Personal bests==