Toxic Thread poisons the target and lowers its Speed stat by one stage. Both effects are independent from each other; the target's Speed is still lowered even if it cannot be poisoned (such as if it is a Steel-type or it already has a status condition), and the target is still poisoned even if its Speed cannot be lowered (due to Clear Body or if the stat is already at -6 stages).
If powered up by a Poisonium Z into Z-Toxic Thread, the user's Speed stat is raised by one stage.
Bold indicates a Pokémon gains STAB from this move. Italics indicates a Pokémon whose Evolution or alternate form receives STAB from this move. A dash (−) indicates a Pokémon cannot learn the move by the designated method. An empty cell indicates a Pokémon that is unavailable in that game/generation.
This article is part of Project Moves and Abilities, a Bulbapedia project that aims to write comprehensive articles on two related aspects of the Pokémon games.