Thompson tested positive for two banned substances, according to Tuesday's statement from the league.
Ibutamoren is used to promote the secretion of human growth hormone and is prohibited by the league due to its ability to increase lean body mass. SARM LGD-4033 (ligandrol) is a selective androgen receptor modulator, another anabolic compound.
It's unclear how long Thompson was utilizing the drugs. The 32-year-old is averaging 3.8 points and 3.9 rebounds in 36 games for Cleveland this season. This is his first suspension, and he will lose $726,465, according to Spotrac.
The NBA agreed to stop testing players for marijuana in April 2023. It was a continuation of the league's decision to stop testing in March 2020 due to the pandemic. Random drug tests for human growth hormone and performance-enhancers resumed in the "NBA bubble" and have since continued.
Additionally, the league reserves the right to screen for what it calls “drugs of abuse," such as methamphetamine, opiates and cocaine.
This is Thompson's second stint with Cleveland after he signed with the team during the offseason. He won a championship with LeBron James and the Cavaliers in 2016.
Thompson won't have an immediate opportunity to speak to reporters, as his suspension begins with Wednesday's game against the Milwaukee Bucks.