Former Olympic 1500m champion Asbel Kiprop has received a four-year ban for doping.
The Kenyan, a three-time world champion, tested positive for erythropoietin (EPO) in an out-of-competition test in November 2017.
The 29-year-old had maintained his innocence and claimed his sample may have been tampered with.
But an anti-doping panel said "the case against the athlete is convincingly made out".
The Athletics Integrity Unit (AIU), an independent body which manages all doping-related matters for athletics, also ruled his results and any winnings from November 2017 to February 2018 should go.
"The panel is aware that its order will interrupt and may even terminate the athlete's sporting career and cast a shadow over his impressive competitive record," said an AIU statement.
The panel noted his clean record and "antipathy to doping" - he missed out on being presented with his Olympic gold medal at the Beijing Games in 2008 because the initial winner, Bahrain's Rashid Ramzi, was later found to have been a drugs cheat.
Kiprop had been tipped off about the test by doping control officials whom he later made a payment too, but the panel said it could find no way in which this would have impacted on him giving a positive reading at the test.