The Republic of Ireland international has resumed training with the Championship club after taking three months compassionate leave in Ireland
The former St Patrick's Athletic midfielder was granted leave by the Championship club due to personal reasons but has since returned to training and manager Lee Clark has welcomed the return of the Republic of Ireland international.
"It is great that Keith has now returned to the club," he said. "He underwent a full fitness assessment last week and I'm delighted to say that he is in great shape so, within a few weeks of being back in full training and some reserve team action, he should be ready to push his way back into consideration for first-team selection."
During his leave, Fahey, 30, continued to train with Airtricity Premier Division side Shamrock Rovers, in order to maintain his fitness levels and he spoke of his appreciation of the support shown by both Birmingham and Rovers.
He said: "I want to thank the club for giving me the necessary time and support to deal with what was a genuinely personal family matter, I appreciate it greatly.
"Over the last few weeks I have been doing the equivalent of pre-season training with my local club Shamrock Rovers and I would like to thank that club’s manager, Trevor Croly, for allowing me to do so.
"While I need to achieve match fitness I believe I am close to being ready to return to Championship football. I now want to contribute fully to Blues' campaign for the remainder of the season," added Fahey.