The 28-year-old has been named in head coach Slaven Bilic's Croatia squad for the friendly clash with Scotland at Glasgow's Hampden Park on March 26. Having not played for his country since October 2006, Klasnic is on course to fulfill his dream of playing in June's Euro 2008 tournament, but it has been a long and hard road back.
"This is a fantastic acknowledgement for me," he said on the Bremen website. "A return to football, and then to the national team, has always been my target during this difficult phase in my life."
Should he face the Scots, Klasnic will become the first footballer in the world to return to international competition after a kidney transplant. It will be an extraordinary comeback.
In January 2007 Klasnic - with 26 caps to his name and eight goals for Croatia including the 2006 World Cup campaign - suffered kidney failure. His body rejected the first kidney donated by his mother, but a second operation was successful after his father, also called Ivan, donated a second kidney in March.
But his life will never be the same again.
From the moment he wakes up, Klasnic must swallow three tablets a day, including a immunosuppressive drug for which he needs UEFA authorization as it on the banned list of drugs but stops his body rejecting the donated kidney.
"It's part of my life now and there is the same dose in the evening," Klasnic told German magazine Sport Bild.
Doctors have told him not to drink alcohol, take care of his diet and even sunbathing is off the menu as his medication carries an increased risk of skin cancer as a side effect.
He made his Bundesliga return in November and formally announced his return in December with two goals at Bayer Leverkusen on his third appearance since the operation.
Klasnic has no problems with the sacrifices he has made, "because I always wanted to return to the Bundesliga stage" and wears a fibre-glass kidney protector whenever he trains or plays.
Important goals against Nuremberg and Braga in the UEFA Cup followed in February which impressed Bilic, whose side face Germany, Poland and Austria at Euro 2008 in June.
"I have planned with Ivan in mind," Bilic told Sport Bild. "What Ivan has done is unbelievable, in Croatia, he is heralded as a public hero."
Croatia's leading newspaper Vercernji list presented Klasnic at the end of last year with the annual prize as an outstanding sportsman - the Brave Heart 2007.
The son of Croatian immigrants, Klasnic played his football in his home town of Hamburg before leaving St Pauli for Bremen in 2001. His biggest achievement was as part of the 2004 Werder team which won the German league and cup double, but his contract runs out in June 2008 and Bremen are stalling.
Werder Bremen club manager Klaus Allofs has been surprised how fast he has returned to first-team football - Klasnic was banned from training with the team in August because the team doctors thought his body would not cope.
And there are still no guarantees what effect minor injuries or illness will have and he has only made eight appearances for Bremen's first-team since his return.
Bremen's delaying tactics have not impressed Klasnic, especially with Werder's rivals Hanover showing interest. But whatever happens from now on Klasnic insists he wants to use his
profile as an international footballer to raise awareness of the need for kidney donors to give people like him another chance in life.
"I want to help others and appeal to others to donate. I hope my fame will help with that."