Stuart Brennan, City's correspondent for the Manchester Evening News, posted the news on Twitter, stating that the 24-year-old's affliction is "not life-threatening".
He tweeted: "Scott Sinclair in hospital with a blood clot in his shoulder. Said to be 'comfortable, and not life-threatening'.
"Happened yesterday while still in Manchester, City expect to know more about his condition in next 48 hours.
The Citizens drew 0-0 with the winger's former team Swansea City this afternoon.