The monthly transformation of a werewolf is extremely painful if untreated and is usually preceded and succeeded by a few days of pallor and ill health. The werewolf may display irritation towards friends. While in his or her wolfish form, the werewolf loses entirely its human sense of right or wrong. However, it is incorrect to state (as some authorities have, notably Professor Emerett Picardy in his book Lupine Lawlessness: Why Lycanthropes Don’t Deserve to Live) that they suffer from a permanent loss of moral sense.

While human, the werewolf may be as good or kind as the next person. Alternatively, they may be dangerous even while human, as in the case of Fenrir Greyback, who attempts to bite and maim as a man and keeps his nails sharpened into claw-like points for the purpose. Though werewolves usually only infect their victims through biting, they sometimes take it too far and kill their victims.

Without any humans nearby to attack, or other animals to occupy it, the werewolf will attack itself out of frustration. This leaves many werewolves such as Remus Lupin with self-inflicted scars and premature ageing from the difficult transformations.