Lasogga joined Championship club Leeds from German side Hamburg in the summer transfer window.
The 25-year-old striker made the switch on a season-long loan deal on transfer deadline day.
The former Germany Under-21 international has been on the books of Hamburg on a permanent contract since 2014 following a loan spell from Hertha Berlin.
According to The Yorkshire Evening Post, Hamburg paid Hertha a transfer fee of £8 million in order to secure the services of the striker.
Lasogga is expected to be replacement for Chris Wood, who joined Burnley from Leeds in the summer transfer window.
Wood was one of the best players in the Championship last season and scored as many as 27 goals in the league.
Leeds head coach Christiansen has spoken highly of the German striker, and told The Yorkshire Evening Post when asked if Lasogga was a direct replacement for Wood: “He’s not the only striker we have brought in.
“But he is a very good striker, experienced, and from what I have seen and from what I knew about him before is that he has a confidence when he is in front of the goal. His abilities are very good.”