Er, do the Cullens use the restroom?

No
They dont the blood they drink get used up as energy

Because I dont like twilight 你 caused me to burst out laughing- Thanks. To answer the 问题 I dont know 或者 care.

I remember 阅读 SMeyer's answer to this one somewhere in her site: no, they don't. She didn't explain where the blood goes, but neither did Bram Stoker 或者 Anne Rice, for instance *shrugs*

perhaps it just dissolves and then when its all gone thats when they thirst for more?

Um, random! random! idk

No, but they get periods XD

Lol, another plot hole SMeyer overlooked...

Um I really don't know but in the 图书 the never use the restroom. But 你 never know if they wear diapers 或者 pampers 或者 if they wet their couches 或者 carpets(since they have no beds) 或者 if they do their business on the floor 或者 in a plant pot........but I really don't know.

To be honest, most fictional characters never use the toilet, whether they're human, vampire, werewolf, elf, hobbit, whatever...I think writers get a little too squeamish about it. Even in Harry Potter, the toilets were only used for brewing Polyjuice potion and taunting Myrtle ^_^

no they don't need to go to the bathroom

Meyer's 吸血鬼 are clearly just straight up magic (like with the psychic powers and elemental abilites) so that's the easy answer; but that's boring. I like scifi and thought experiments so let's work through it. I think Meyer herself has explicitly 说 her 吸血鬼 don't poop. For the 问题 of "where does it go?", it actually could be exhaled. The "C" in the CO2 we exhale actually comes from the 食物 we've eaten. As it gets broken down to smaller and smaller parts some of it eventually reaches individual CO2 molecules. It's plausible that the vampire digestive systems are so efficient they can break down their blood meals to gases that can be exhaled. In fact, that could explain why they may have horrible breath that smells of rotting flesh; they need to exhale gaseous sulfur and phosporous compunds. But, this doesn't apply to Twilight 吸血鬼 specifically; Bella certainly never mentions it. Twilight 吸血鬼 can clearly still breathe as they do to smell and I'm pretty sure it is mentioned most of them still breathe out of habit, but they can hold their breaths indefinitely. This explanation would require them to breathe at least sometimes but no where does it say Twilight 吸血鬼 NEVER breathe. This could actually even apply to iron. Iron can bond to soluble organic compounds (afterall, that's how it exists in our blood without getting chunks of iron in our bloodstreams). So, iron and other difficult to vaporize elements 或者 compounds could be sweated out 或者 otherwise excreted as a liquid. Again, Meyer has mentioned her 吸血鬼 don't sweat 或者 pee but there is another way. 吸血鬼 could cough 或者 sneeze. The dissolved iron could be expelled in tiny droplets just like how liquids are expelled as aerosols when we cough (like bacteria being scattered when we're sick). I'm really into scifi so I 爱情 these kinds of 问题 :).