[header] How to check a cat for fever [title] Look for behavioral changes. [step] If your cat is normally playful, active, and generally friendly, reclusiveness could be a sign that your cat is sick. If it starts hanging out under your bed, couch, table, or any other out of reach, unusual place, this could be a sign. 
Cats are instinctively cautious creatures, even if they might be playfully curious on any given day. If your cat is sick, it will want to reduce his or her vulnerability by hiding from you.