"Mario won't be with us at the Confed Cup," said Loew at an event in Hamburg.
"He should take the time, which he needs, to be fit and well again for pre-season training for next season."
Loew revealed Goetze is "responding well" to treatment: "one thing is certain, he will make a full recovery and will be able to play again."
Goetze scored the winning goal for Germany in the 2014 World Cup final, but has been sidelined since February after his club Dortmund revealed he has an unspecified metabolism disorder.
"It was a relief for him to get to the bottom of the matter and find an important reason for it," said Loew.
Germany have been drawn with Australia, Cameroon and Chile in Group B at the Confederation Cup, June 17-July 2.
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