A poisoned Pokémon will take damage equal to 1/16 of its maximum HP every turn, after it attacks, or at the end of the turn if it did not attack. If a poisoned Pokémon causes an opponent to faint, the poisoned Pokémon will not take damage that turn. Outside of battle, all poisoned Pokémon lose one HP for every four steps taken.

A badly poisoned Pokémon takes damage equal to 1/16 of its maximum HP (rounded down, but set to 1 HP if it would be less) on the first turn, after which damage increases by 1/16 each time it takes poison damage. The damage stops increasing when it equals 15 * floor(maximum HP / 16). When a badly poisoned Pokémon is affected by Haze, switches out, or when the battle ends, its poison status becomes regular poison.

If a Pokémon badly poisoned by Toxic is also under the effect of Leech Seed, both types of recurrent damage will draw upon the same N value to calculate how many multiples of 1/16 of the Pokémon’s HP is taken as damage, and both will increase that value. If a badly poisoned Pokémon successfully uses Rest, it will be cured of poison, but N is not reset; if it then suffers burn, Leech Seed or poison damage, that damage will draw upon the N value, and the N value will still increase by 1 each time (however, if the Pokémon is poisoned with Toxic, the N value will be reset to 1).