Balotelli did not feature for the Reds in the quarter-final replay at Ewood Park on Wednesday evening and attracted criticism for not playing.
However, the Italian striker posted an Instagram photo of himself holding a thermometer which read 38.7 degrees – a temperature over 38 degrees is usually considered reason for concern.
Balotelli also posted a message which read: “Nothing stop me to watch my team winning (at least this time you know the real reason why I am out). Miss the pitch so much #unluckyseason #YNWA #illbeback.”
The message came just days after Balotelli attracted some criticism for announcing himself unavailable to play in the 4-1 defeat at Arsenal due to a “slight knock” he suffered at training.
Liverpool manager Brendan Rodgers confirmed Balotelli’s latest sickness, saying the 24-year-old had travelled with the team, trained, and stayed at the team hotel, but fallen ill overnight before being sent home on doctor’s advice.
Balotelli, 24, has had a muted season at Anfield since joining the club for £16m from AC Milan in August.