Gundogan targets Dortmund return
The Germany international has played only once for the club in the Bundesliga this term due to a back injury.
However, he is aiming to return immediately after the winter break when Jurgen Klopp's men host Augsburg on January 25.
Gundogan has trained with his team-mates in recent weeks and plans to use the break as an opportunity to complete his recovery.
"Of course I'm glad that, for the first time in a while, I was able to train with the team after this difficult time," he told Bild.
"I hope to maintain progress while on holiday, so I can then attack fully the Bundesliga restart."
Dortmund have slipped to fourth place in the table following a poor run of form, and sporting director Michael Zorc says the club are "totally relieved" to have Gundogan back.