Steve Bruce's side are labouring in the Premiership, having won just three games so far, but the skipper points out that two fellow strugglers provided genuine tests for the team in our last two home outings.
"We won't take anything for granted," said Ledley. "Sunderland and Portsmouth both gave us a tough game and Birmingham will do the same.
"We know they have got good players, Heskey is always a handful up front and they are looking to turn things around. It will make it a tough game from our point of view."
Ledley added that it has been a surprise to him seeing Birmingham at the wrong end of the table and insists he does not want them to turn their season around with the help of any reward at the Lane.
I am surprised because they have got a good manager and good players
They have had some injuries, but they have got a good enough side to suggest they shouldn't be where they are.
"It takes a lot of hard work, they say the league table doesn't lie so they obviously haven't been doing as well as they should.
"We have to treat it like we have every home game this season and go for the three points again. We want to keep our form going and, after a draw, we want to come back with another win as quickly as possible and Birmingham will be the right time.
"Christmas is important because the games come so close together. You can move up quickly or move down the table just as quickly depending on how you do. You've got to keep your focus, the lads have got to look after themselves over Christmas and we have to be ready for the games."
Ledley King is expecting nothing other than a real Boxing Day battle when Birmingham come to town for the 1pm kick-off at the Lane.