Since 1998 she attended Sing"ore Girls High School near Iten, famous for producing Kenyan women athletes. She attended the Kenyan trials for 1999 World Youth Championships, but as 400 m hurdles was not competed at the trials, she opted to take part in 800 m. She finished second and was selected for the Kenyan team, but failed to reach the final of 800 m competition in World Youth Championships held in Bydgoszcz, Poland.
Janeth, nicknamed "Eldoret Express" is from Kabirirsang, near Kapsabet. Famous athletes Wilson Kipketer and Wilfred Bungei are also from the same village. She started athletics while at Kapsumbeiywo Primary School and took several events.
Her record from that event still stood in 2012.
Her speciality at the time was actually 400 m hurdles. She joined International Olympic Committee-sponsored High Performance Training Centre in Eldoret in 2001.
She was then coached by 1988 olympic gold medalist Paul Ereng. The same year, she took 800 m silver medal at the African Junior Championships, and the next year she took 800 m gold medal at the World Junior Championships in Kingston, Jamaica.
Janeth Jepkosgei took part at the 2003 All-Africa Games, but failed to reach the 800 m final.
She did beat the "B"-qualifying time, but Athletics Kenya did not sent her or any other Kenyan 800 m female runner to represent Kenya at the world championships. Her breakthrough year was 2006. She managed to beat veteran runner Maria de Lurdes Mutola of Mozambique.
She also beat Kenyan 800 m women"s record twice.
She retained the Kenyan Sportswoman of the Year award. On 24 May 2008 the 19-year-old Pamela Jelimo set a new Kenyan record of 1:55.76, beating the one previously held by Jepkosgei.
She collided with Caster Semenya of South Africa such that Jepkosgei fell and finished last in her heat at the 2009 World Championships. Jepkosgei is now coached by Claudio Berardelli.
Her manager is Federico Rosa.
800 metres – 1:56.04 (2007)
1000 metres – 2:37.98 (2002)
1500 metres – 4:02.32 (2011)
One Mile – 4:28.72 (2008).
She won national secondary school championship in heptahlon, while still at form one. In 2000 Jepkosgei won two gold medals at national secondary school championships, the events were 400 m hurdles and 800 m. At the East Africa Youth Championships held in the same year she won 400 m hurdles, while at 800 m she finished second. In 2004 she won Kenyan Olympic trials at 800 m, but was not selected since she failed to beat qualifying time. The history repeated itself in 2005, when she won 800 m at national trials, but did not secure an "A"-qualifying time. On 24 March 2006 she won the women"s 800 m event at the 2006 Commonwealth Games with a time of 1 minute, 57.88 seconds. Later same year she won African Championships in Athletics at the 800 m event. Jepkosgei was awarded the 2006 Kenyan Sportswoman of the Year award. Jepkosgei made Kenyan History on 28 August 2007, where she won gold in the World Championship 800 m final in Osaka, becoming the first female Kenyan middle distance runner to achieve gold over 800 m. She led from start to finish to win in a time of 1 minute, 56.04 seconds, beating the Kenyan record and world leading time (156,18) she had set at the heats two days earlier. Jelimo"s dominance throughout the season prevented Jepkosgei from major victories, but won Olympic silver medal over 800 m. However, after a successful protest, she was allowed to run in the semi-finals and eventually achieved silver medal, well behind the winner Semenya. Jepkosgei started her 2010 season by a win at the Diamond League meeting in Shanghai, China.
