The England right-back was a late withdrawal from the team to face Arsenal at the Emirates on Saturday due to illness.
The 29-year-old was admitted to hospital after complaining of severe pain on the right side of his face and jaw, and was replaced by youngster John Flanagan for the 2-0 defeat to the Gunners.
Johnson underwent scans in hospital which showed signs of a localised infection, according to Liverpool's official website.
However he was later discharged from hospital and allowed to return home on Saturday evening.
He is expected to return to training in the next few days and the club's medical staff expect him to be available to face the Cottagers at Anfield.