In 2013, at the age of 13, Kiptum finished 10th in his first
half marathon, the Family Bank
Eldoret Half Marathon in
Kenya. In 2014, he finished 12th; in 2018, he finished first, self-coached at the time. In March 2019, Kiptum participated in his first international race, the
Lisbon Half Marathon, finishing fifth with a new personal record (59:54). He participated in six other races that year, touring north and west Europe, In 2020, Kiptum started working with Rwandan
3000 metres steeplechase record holder
Gervais Hakizimana as a coach, although Kiptum supposedly had periodically trained alongside other youths with him since 2013. In April 2023, Kiptum set the course record at the London Marathon (2:01:25), only 16 seconds slower than the world record at the time and 72 seconds faster than Kipchoge's course record (2:02:37). His following race, which was his third marathon and second World Marathon Major, was the
Chicago Marathon on 8 October 2023, when he was still aged 23. Kiptum set a new world record with a time of two hours and 35 seconds, slicing 34 seconds off Kipchoge's standard set at the
2022 Berlin Marathon, and surpassing the course record by more than three minutes. Kiptum negative split again, but this time the first half was covered in 60:48, almost a minute faster than his performance in London (though still 14 seconds behind the world record pace), and he had the stamina to run his second half at 59:47—only two seconds slower than in London, where he set the quickest half in a marathon. As in Valencia and London, the Kenyan made his trademark move roughly near the 30K checkpoint. After the 29th kilometre in a fast 2:35, he clocked a record 13:35 from 32–37k at a swift 2:43 min/km pace (22.09 km/h). Thus, Kiptum averaged 2:51 min/km pace for the entire distance (20.995 km/h). He ran at the front after the 15K checkpoint, without a
pacemaker after halfway, and alone from 30th kilometre onward, beating the runner-up—his compatriot
Benson Kipruto—by almost three and a half minutes. ==Training regimen==