Just because your kitty occasionally trembles doesn't mean he's a "scaredy-cat." Like humans, cats may shiver or shake for any number of reasons -- from fear, to a fever. A temporary case of the jitters is probably nothing to worry about, but if your cat continues to quake and you don't know why, give the veterinarian a call. An examination might be in order.
Your cat may not like winter anymore than you do. If he's prone to shivers when the temperature plummets, chances are he's just cold. Like humans, cats will tremble in frigid temperatures to help their body generate heat. Bring your outdoor cat inside when it's cold. If you notice neighborhood strays roughing out the winter, be kind and put a cardboard box with an old blanket on your back porch or in your garage. Provide your indoor kitty with a warm bed by the radiator or a lengthy snuggle on the sofa with his favorite person.
Your cat may shake when she gets the jitters. Nervous excitement, anxiety or fear can trigger a release of adrenaline in your cat's body, making her tremble. Soothe her upset by speaking to her in a calm, quiet tone or distracting her from whatever has her riled up. Never attempt to pick up or pet a cat who appears visibly frightened or angry. She may misdirect her fearful aggression and scratch or bite you. Cat scratches -- even mild ones -- can lead to serious bacterial infections that may require IV antibiotics or long-term treatment. If you can't take your kitty's mind off her troubles, it's best to leave her alone, and let her work it out.
Age or Infirmity
Older cats may develop muscle weakness or arthritis, making them tremble when they move. If your cat has had an accident or mishap, he may be sore, and his muscles may quiver due to pain or weakness. Nerve damage, neurological impairment, bacterial or viral infections, thyroid disease, an electrolyte imbalance and dehydration due to illness may all cause trembling in a cat. Take your kitty to the vet if his trembling continues.
Allergies, Poison, Bites
If your cat is taking medication or has been vaccinated recently and begins to tremble, it could be a sign of an allergic reaction -- a potential emergency that calls for a vet visit right away. Likewise, if you suspect your trembling cat may have eaten something poisonous or been bitten by a spider or insect, speak to your vet. Most insects and spiders are not poisonous, but your cat could be allergic to the venom or saliva in a bite.
Fever or Shock
A cat that has been injured may suffer from shock, causing her to shake. Because shock can be a life-threatening condition, take your cat to the vet anytime you suspect she may have suffered a serious injury. Though usually not life-threatening, a high fever may give your cat the shivers as her body tries to regulate her temperature. Your cat's normal temperature can range anywhere from 100.2 degrees Fahrenheit to 102.5. A fever higher than 106 degrees Fahrenheit can cause organ damage. Seek immediate veterinary care.