Hiding more than usual
Acting withdrawn or less social
Sudden aggression or irritability
Hissing, growling, or swatting when touched
Limping or avoiding use of a limb
Reluctance to jump, climb, or use stairs
Stiff or hunched posture
Restlessness or inability to get comfortable
Excessive grooming of one area
Not grooming at all
Loss of appetite
Drinking less or more than usual
Changes in litter box use
Crying, yowling, or unusual vocalizing
Rapid breathing or panting
Dilated pupils
Ears held back or flattened
Tail tucked or held differently
Trembling or shaking
Sleeping more than usual
Sensitivity to being picked up or handled
Facial tension or squinting
Weight loss
Vomiting or diarrhea
Seeking warmth or isolation unusually
Any sudden change in normal behavior