K iodide (KI) is not completely shelf stable, it oxidizes slowly in air (into elemental iodine, which is unsuitable to be ingested as a iodine source for humans).
K iodate (KIO3) is completely shelf stable, but it can be unpleasant when taken in very large doses.
K iodate (KIO3) is completely shelf stable, but it can be unpleasant when taken in very large doses.