Liberia goalkeeper banned for doping violation
World soccer's governing body said the test, following the June 21 game against Senegal, had shown traces of a glucocorticoid.
The substance is specified by the World Anti-Doping Agency (WADA) as a form of medication which athletes can use if given prior permission in the form of a therapeutic-use exemption.
FIFA said King had not obtained the necessary exemption.
"The sanctions for such an anti-doping rule violation range from a warning to a two-year suspension," FIFA said.
"The FIFA disciplinary committee decided to impose a sanction of five months starting on October 2, 2008, the date on which the player was first provisionally suspended."
FIFA added King's ban would apply to all domestic and international competitions, including friendly matches.