A character cannot spend so much XP on anitem that he or she loses a level. However, upon gaining enough XPto attain a new level, he or she can immediately expend XP oncreating an item rather than keeping the XP to advance a level.
Quote from: PHBA character cannot spend so much XP on anitem that he or she loses a level. However, upon gaining enough XPto attain a new level, he or she can immediately expend XP oncreating an item rather than keeping the XP to advance a level.So you definitely can't level drain yourself, and "saving" the xp isn't RAW, though having to stop mid-combat to craft your item because you dinged on monster 3 of 7 seems unreasonable.