Check out this list of some symptoms that require your cat to see a veterinarian. Remember that when in doubt, day or night, don't wait: Call a veterinarian!

• Seizure, fainting, or collapse.
• Eye injury, no matter how mild.
• Vomiting or diarrhea — anything more than two or three times within an hour or so.
• Allergic reactions, such as swelling around the face, or hives, most easily seen on the belly.
• Any suspected poisoning, including antifreeze, rodent or snail bait, or human medication. Cats are also especially sensitive to insecticides (such as flea-control medication for dogs) or any petroleum-based product.
• Snake or venomous spider bite.
• Thermal stress — from being either too cold or too hot — even if the cat seems to have recovered. (The internal story could be quite different.)
• Any wound or laceration that's open and bleeding or any animal bite.
• Trauma, such as being hit by a car, even if the cat seems fine.
• Any respiratory problem: chronic coughing, trouble breathing, or near-drowning.
• Straining to urinate or defecate.