The Lions had been on a magnificent 13-game unbeaten run but were swept aside at Portman Road, after two goals from DJ Campbell and one from Daryl Murphy.
The win made it 16 points from a possible 24 since McCarthy replaced Paul Jewell, but the Town boss remains realistic about the club's hopes.
He said: "I like the fact our supporters are getting excited but I'm not getting carried away. We've got Leeds away next weekend and then a really tough Christmas period.
"Everyone is starting to talk differently, rather than about staying up, but I'm just happy with the points."
McCarthy again underlined his desire to keep Campbell at the club, after the on-loan QPR striker took his tally to eight goals in 12 games.
He said: "I left (QPR boss) Harry Redknapp a message the other day but I think he's got plenty on at the moment.
"We can't do anything about it anyway. It'll run its course but other people will be interested because he's scoring goals.
"He wants to sign for a club permanently and we'd like to take him, but there will be mitigating circumstances."