Bladder

The bladder meter decreases naturally throughout the day, and can only be increased by going to the toilet. Upgrading to a better toilet can boost Comfort whilst the Sim is relieving him or herself. If a Sim's bladder starts to get full, they become extremely cranky; when it gets to the red, they make a wild dash for the toilet with urgency, and if they can't get there in time, the poor Sim has an embarrassing accident on the floor, which will severely affect the Sim's Hygiene bar. In The Sims and The Sims 2, drinking a cup of coffee can make the bladder meter decrease. If Sims do not flush the toilet, it can eventually become clogged, resulting in a mess that someone will have to clean up.

In The Sims 2 and The Sims 3, Sims have to train toddlers in order to let them use the potty by themselves. They will wet themselves if not potty trained. An older Sim can click on the potty chair and potty train the toddler.

As a rule, community lots will have public toilets of some sort. In The Sims 2, Knowledge Sims and/or neat Sims may occasionally have a minor fear of using a public toilet. "Having an accident" is a fear in The Sims 2, though it takes away more influence than aspiration.

In The Sims 2, outgoing and sloppy Sims are also able to "use" shrubs and the AquaGreen Hydroponic Gardento relieve their bladder needs. Sloppy Sims will also pee while taking a shower if their bladder need is low enough. In The Sims 2: Pets Werewolves can use the Howl interaction to lower non-werewolves' bladder needs,

In The Sims 3, the Steel Bladder lifetime reward makes it so that Sim who purchased it no longer has to use the bathroom again. Also, Sims gain an "Embarrassed" moodlet for wetting themselves, which gives -20 mood for 3 hours; and their hygiene drops to 0.

Bladder and other Life States

 * For SimBots, the equivalent of bladder is Waste Buildup. Servos and Plumbots do not have a bladder motive.
 * PlantSims do not have a bladder motive.
 * Mummies do not have a bladder motive.

Trivia

 * The Sims Medieval does not feature the bladder meter. Instead, a Sim using a chamberpot gains a temporary buff.
 * In the real world, humans also have bladders and pee.