Career
His personal best in the men"s shot put currently stands at 20.78 m, which he put on August 4, 2001 in the World Championships in Edmonton, Canada. He was coached by Robert Malmberg. Karlsson was the 18th member to be inducted into the 20 meter club after he successfully putted the shot 20.45 m in a competition on May 31, 2001 in Espoo, Finland.
He had to end his career early 2007 due to colitis ulcerosa.