[5] Her high school games teacher Philip Ng'eno remarked that she used to compete with the boys in sprint events as the girls did not provide the competition she needed.

[3] The family was poor and struggled to pay the fees to send Jelimo to secondary school – her two older siblings had already dropped out as they were unable to meet the costs.

By 2004, Jelimo had reached the local provincial championships in the 400 m.[4] Maru continued his generosity, allowing the young athlete to graduate while she still owed one year's worth of fees.

[6] She kept improving throughout the season, winning the 400 metres gold medal at the African Junior Championships with a finish of 54.93 s and setting a Kenyan national junior record in the 200 m with 24.68 s. Jelimo was pleased with her accomplishments but her new coach Zaid Kipkemboi Aziz suggested that she change to 800 m, stating that she would perform best over the longer distance.

[4] Jelimo ran her first 800 metres race on 19 April 2008 at the Kenyan trials for the African championships, clocking 2:01.02 minutes.

[11] On 1 June 2008 she ran an impressive 800 m race in Berlin and won the ISTAF Golden League in 1:54.99, a new African record.

It was also her fourth consecutive win in ÅF Golden League, where she was one of only two remaining jackpot contenders, the other being high jumper Blanka Vlašić.

[13] She continued her unbeaten streak by winning the Weltklasse Golden League meeting in Zurich on 29 August 2008 improving her personal best to 1:54.01.

At the Memorial van Damme competition in Brussels, the ÅF Golden League final, Jelimo won the 800 metres with a time of 1:55.16.

[19][20] [21] Instead, she started her season in April at the Athletics Kenya meeting in Kakamega, running 200 and 1500 metres races for training purposes.

[27] Jelimo returned to competition in April 2010, winning the 800 metres race at the Athletic Kenya meeting in Nakuru.

[33] She was beaten by Fantu Magiso at the Golden Gala, but was victorious at the Kenyan trials and then set a world-leading time of 1:56.76 at the KBC Night of Athletics.

In November 2015, the World Anti-Doping Agency recommended two Russian women who finished in first and third be given lifetime bans for their doping violations at the Olympics.