The 28-year-old Swedish international lost consciousness at home on Tuesday, February 20, 2024, and was taken to Aarhus University Hospital, where he was admitted and placed on a ventilator.
Tests revealed that he had experienced multiple blood clots due to a rare inflammation of the blood vessels in his brain, putting his life in serious jeopardy.
Olsson spent several weeks in the hospital battling for his life, but thanks to timely medical intervention, the 29-year-old's life was preserved.
Reflecting on the initial weeks following his collapse, he stated: "I was essentially dying. I was unreachable and have no recollections from that period."
He added, "I've overcome the worst part. I've had to think positively, and exercise patience with everything."
The Swede persevered Arsenal’s academy and made one appearance for the Gunners before opting to join FC Midtjylland after a successful loan period in 2015.
Olsson was also present in the stands when FC Midtjylland secured the Danish championship on May 26, 2024.
In March 2025, the midfielder terminated his contract with FC Midtjylland after gradually working his way back to the training field, with the intention of returning to Sweden.
He then left FC Midtjylland to sign a new contract with his childhood club IK Sleipner, competing in the third tier of Swedish football.
On Saturday, Kristoffer Olsson finally completed his long journey back to action when he started in a training match against Österåker United, where he netted an impressive goal after 14 minutes of play.
Olsson, who has earned 43 caps for the Swedish national team, has also played for Krasnodar and Anderlecht, in addition to featuring in 70 matches for FC Midtjylland in the Danish Superliga.