Lillard is now on blood-thinning medication and will undergo regular testing.
"Damian's health is our number one priority," said Bucks General Manager Jon Horst. "We will support him as he moves through this weekly process of strict criteria to ensure that it is safe for him to return to play. Doctors have indicated that his situation is very unlikely to occur again. We are thankful that this was identified and medicated quickly."
The news comes not long after San Antonio Spurs young star Victor Wembanyama was ruled out for the season with a blood clot in his shoulder.
Former NBA champion Chris Bosh retired from the league after being diagnosed with a blood clot as well.
The Milwaukee Bucks are currently 41-33 and just above the Detroit Pistons in the Eastern Conference standings, sitting at fifth place.