Former light-welterweight world champion Khan announced his retirement in May after his sixth-round stoppage defeat to fellow Briton Kell Brook (36) on February 19 but would be unable to return to the ring until April 2024.
The UKAD website states that ostarine is a drug designed to have similar effects to testosterone. It is present on the World Anti-Doping Agency's prohibited list as an anabolic agent and is prohibited in sport at all times.
Khan, who had expressed concerns over a lack of drug testing before his fight against Brook, accepted that he broke anti-doping rules but said it was not intentional.
"I've never cheated in my life," Khan told Sky Sports. "You can see by my performance against Kell Brook... If I went in there and knocked Kell Brook out it's different
"I was the one who wanted testing on the fight. The amount that was in my system could have been by shaking people's hands... I don't even know what drug was in my system."
An independent tribunal accepted Khan's argument and ruled out "deliberate or reckless conduct" in a written decision dated Feb. 21, 2022 and imposed a two-year ban from all sport due to "strict liability".
"Strict liability means athletes are ultimately responsible for what they ingest and for the presence of any prohibited substances in a sample," UKAD chief executive Jane Rumble said.
Khan's ban began on April 6, 2022 and will expire on April 5 next year.
"I'm a retired fighter, it's funny they've given me a two-year ban now," Khan added.
Khan won a silver medal at the 2004 Athens Olympics as a teenager and turned professional a year later.
He won the WBA light-welterweight title with victory over Ukraine's Andreas Kotelnik in 2009 and added the IBF title in 2011 when he beat American Zab Judah.
Khan retired with a record of 34 wins and six losses, although his defeat to Brook was disqualified by the panel.