A cat shaking or twitching while lying down is usually just dreaming. During REM sleep, cats experience brief, jerky muscle twitches throughout their body, driven by bursts of activity in the brainstem. This is completely normal and nothing to worry about. But if your cat is awake and visibly trembling, the cause could range from being cold to something that needs veterinary attention.
Twitching During Sleep
The most common reason a cat shakes while lying down is simply that it’s asleep. REM sleep naturally produces small, involuntary muscle twitches across the body. These movements originate deep in the brainstem, not from the parts of the brain that control voluntary movement. You might see paws paddling, whiskers fluttering, the tail flicking, or small jerks in the legs and face. The twitches are brief and random, and your cat will look relaxed between them.
The easiest way to tell if your cat is just dreaming: their eyes are closed (or half-closed with the third eyelid visible), their body is otherwise limp, and the twitching stops within seconds or when they wake up. If you say their name or make a noise and they startle awake looking normal, there’s nothing going on.
Your Cat Might Be Cold
Cats have a normal body temperature between 99.5°F and 102.5°F. If their internal temperature drops below 98.5°F, they’re hypothermic and will start shivering. This is more likely in very young kittens, elderly cats, thin or underweight cats, and cats that are wet or in a drafty space. If your cat feels cold to the touch, especially on the ears and paws, warming them up with a blanket and moving them somewhere warmer should stop the shaking. If it doesn’t, or if your cat seems lethargic and unresponsive, that’s a sign of more serious hypothermia.
Pain Can Cause Trembling
Cats in pain sometimes tremble or shake while resting, though they rarely vocalize. Since they’re good at hiding discomfort, look at the face for clues. A cat in pain typically shows a specific set of changes: ears rotated outward with the tips pulled apart, squinted or tightly closed eyes, a flattened muzzle, whiskers pushed forward and stiff (almost spiked), and the head held low, below the shoulder line or tilted with the chin toward the chest. If your cat is shaking and showing several of these facial signs, pain is a likely cause. Common sources include dental disease, urinary blockages, arthritis, and abdominal problems.
Low Blood Sugar
Hypoglycemia causes visible trembling in cats and can come on while they’re resting. It’s most common in diabetic cats receiving insulin, very young kittens who haven’t eaten, and cats who’ve been vomiting or refusing food for a day or more. Along with trembling, you may notice anxiety, pacing, vocalization, rapid breathing, or vomiting. This is urgent because blood sugar can continue dropping, potentially leading to collapse or seizures.
Toxin Exposure
One of the most dangerous causes of shaking in cats is accidental exposure to permethrin, a flea-control insecticide found in many dog flea products. Cats lack the liver enzymes to process it, and even a small amount can be toxic. In a study of 42 cats with permethrin poisoning, 86% developed tremors or muscle twitching, 41% had localized twitches, and 33% had full seizures. Most of these cases happened when a dog flea product was applied directly to a cat, or when a cat groomed a recently treated dog.
Symptoms typically appear within a few hours of exposure but can be delayed up to 72 hours. The tremors are often generalized, meaning the whole body shakes, and they don’t stop on their own. If you’ve recently applied any flea product to your cat or to a dog in the household, and your cat starts trembling, this is a veterinary emergency. Washing the cat in lukewarm (not hot) water with mild dish soap can help remove the chemical from the skin, but the cat still needs professional treatment for seizure and tremor control.
Focal Seizures
Not all seizures look like the dramatic, full-body convulsions you might picture. Focal seizures affect only one area of the brain and can produce subtle signs: twitching on one side of the face, a single limb jerking, or “fly-biting” episodes where the cat snaps at the air as if catching invisible insects. These episodes often start without warning while the cat is resting or relaxed. Unlike sleep twitching, the cat is awake during a focal seizure. In many cases, cats remain aware of their surroundings and can even be distracted out of the episode by their owner.
If you notice these episodes happening repeatedly, try to record one on your phone. Video is enormously helpful for a vet trying to distinguish focal seizures from normal behavior.
Hyperesthesia Syndrome
This condition causes extreme skin sensitivity, almost always along the back and especially near the base of the tail. A cat with hyperesthesia may have rippling skin along the spine, dilated pupils, drooling, and sudden bursts of frantic grooming or running. It can look like twitching or shaking when the cat is lying down, particularly if something touches or even lightly brushes the sensitive area. The cause isn’t fully understood, but it’s considered a neurological condition. It tends to appear in younger adult cats and can be managed with veterinary guidance.
Signs That Need Immediate Attention
Some combinations of symptoms alongside shaking point to an emergency. Rapid breathing, especially open-mouth panting, is never normal in a resting cat. Pale or white gums (instead of their usual pink) signal shock or severe blood loss. A cat that’s trembling and has suddenly dilated pupils may be experiencing a toxin reaction, a blood pressure crisis, or vision loss. Swelling around the face, hives on the skin, or sudden vomiting paired with restlessness can indicate a severe allergic reaction that progresses quickly to collapse.
If your cat is shaking and also shows any of these signs, cool extremities, a weak or rapid pulse, difficulty breathing, or an inability to stand, time matters. These warrant an immediate trip to an emergency vet rather than a wait-and-see approach.