How do I know if my cat is in pain?

My cat sometimes fails to use its litter tray properly

My cat pulls out its fur and licks itself excessively

My cat does not groom itself and its coat looks unkempt

My cat no longer jumps up to high places

My cat avoids being stroked or picked up despite being sociable

My cat has developed aggressive behaviour

My cat does not drink and/or eat like it used to

My cat stays immobile in the same position for a long time

My cat sometimes has a vacant look or half-closed eyes