The Hoops captain suffered a head knock during Saturday's 3-0 defeat to Rangers at Ibrox.
A statement on the club website said: "Doctors were happy with the results of the tests carried out on Stephen.
"His progress will be closely monitored by the Celtic medical team over the next few days."
McManus left the pitch on a stretcher wearing an oxygen mask after losing consciousness.
However he will now join the rest of Gordon Strachan's squad ahead of Wednesday's match in the Estadio da Luz.