How Do You Know if You're Hydrated?

Listen to your thirst reflex. If you thirsty drink water. The hyperthalamus, which picks up the changes in concentration, if things become too concentrated, it's telling you there's not enough water in your body to dilute it. And it does this with very minor changes that are so minor that they're not physiologically significant, but could be if left unchecked. So there the mechanisms you should be listening to and looking at to tell you hydration status.