Cats are famous for hiding illness, so it helps to know the subtle signs instead of waiting for obvious symptoms.

• Changes in litter box habits: Straining, going more or less often, or avoiding the box altogether.
• Eating or drinking changes: Sudden increases or decreases in appetite or thirst.
• Hiding more than usual: Cats often withdraw when they don't feel well.
• Weight loss or gain: Especially if it happens without a diet change.
• Bad breath or drooling: Can point to dental issues that are easy to miss otherwise.

An annual checkup catches most of this early, even if your cat seems totally fine.