The disciplinary board of European soccer’s ruling body found the Frenchman “guilty of using a prohibited method in accordance with the WADA (World Anti-Doping Agency) prohibited list”.
The former France international was playing for Sevilla on loan from Manchester City at the time.
UEFA gave details of the case last month when it said it turned down a request for Nasri in February last year to be retroactively granted a therapeutic use exemption (TUE).
Nasri took his case to the Court of Arbitration for Sport (CAS) which dismissed the appeal in December, allowing UEFA to proceed with a disciplinary case against him.
The 30-year-old, who won the last of his 41 international caps in 2013, rejoined Manchester City at the end of his loan last July and was sold to Turkish club Antalyaspor in August.
He left my mutual agreement at the end of January and is now a free agent. Nasri’s lawyer could not immediately be reached for comment.