The school did not provide additional details. Calhoun had prostate cancer in 2003 and skin cancer twice, most recently in 2008.
Peter Schulman, the coach's primary-care physician, said in a statement that he advised Calhoun to take time off "to address some temporary medical issues, none of which involve any previous medical conditions that he has dealt with."
Associate head coach George Blaney will run the Huskies in Calhoun's absence. UConn is 11-6 and fell out of the top 25 this week after losing three straight. The Huskies host St. John's tonight and top-ranked Texas on Saturday.
"Our primary concern is coach Calhoun's health and his complete recovery," UConn athletic director Jeff Hathaway said. "We will do everything possible to support Coach during this time."
Calhoun usually meets with the media the day before a game. He was not available yesterday - a day earlier, the school said he had prior commitments and a late practice.
Calhoun has won two national championships at Connecticut. He guided the Huskies to the Final Four last season, but missed the Huskies' first NCAA Tournament game in March after being hospitalized for dehydration.
Last June, he was hospitalized after breaking several ribs during a charity bike ride.
"Obviously, I'm concerned," he said. "I hope he's OK. I hope it's nothing too serious, that he's able to come back and that he doesn't end his career this way."