She has a personal best of 2:20:48 for the distance. In the 2016 Olympic Games, at age 31, she won the marathon in warm conditions with a time of 2:24:04, becoming the first female winner from Kenya since women's marathon was introduced to the Olympics in 1984. Sumgong received an 8 year ban (until 2027), after she was tested positive for the banned substance EPO, fabricated her medical records and lied about her whereabouts after the positive test.