The 26-year-old France international failed a dope test following his side's Europa League round of 16, second leg tie against Manchester United last month, a statement said.
"(Sakho) did not request the analysis of the B sample. UEFA has now suspended the player provisionally for 30 days until a final decision is taken by the UEFA Control, Ethics and Disciplinary Body," UEFA said.
France's RMC radio reported this week that Sakho's failed test followed the use of a fat-burning drug.
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He was withdrawn from Liverpool's squad for last weekend's Premier League match against Newcastle United after the club said it had received a formal communication from UEFA.
(Reporting by Martyn Herman, editing by Pritha Sarkar)
