Dillashaw posted on social media that he would give up the belt after he was informed by the New York State Athletic Commission and the United States Anti-Doping Agency of the results of his test leading up to his last fight in January. Dillashaw suffered first-round loss to Henry Cejudo and failed to become a two-division champion.
"While words can't even begin to express how disappointed I am at this time, please know that I'm working with my team to understand what has occurred and how to resolve this situation as quickly as possible," Dillashaw said. "Out of fairness and respect to the rest of the division, I've informed the UFC that I'll be voluntarily relinquishing my title while I deal with this matter."
A spokesman with the New York commission said Wednesday that Dillashaw was fined $10,000 and suspended for one year for drug use, but declined to give further details.
The 33-year-old Dillashaw (16-4) had cut 10 pounds of weight to fight Cejudo. Dillashaw used a program devised by a triathlete math professor and performance specialist to cut some serious weight in his attempt to hold championships in two weight classes.
He's a two-time bantamweight champion and won the title for a second time when he defeated Cody Garbrandt at UFC 217 in November 2017.
More AP sports: https://apnews.com/apf-sports and https://twitter.com/AP_Sports
Copyright 2019 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.