Most of the time, a cat that shivers or twitches during sleep is simply dreaming. Cats cycle through REM sleep just like humans do, and their brains become highly active during this phase, producing small involuntary movements that can look a lot like shivering. That said, there are a handful of medical reasons a cat might tremble during rest, and knowing the difference can save you unnecessary worry or help you catch a real problem early.
Dreaming Is the Most Common Cause
Cats spend a significant portion of their day asleep, and a good chunk of that time is spent in REM sleep, the phase associated with dreaming. During REM, the brain fires rapidly while the body stays mostly still, but some of that neural activity leaks through as physical movement. You might see paw twitches (as if your cat is running or pouncing), ear flicking, whisker movements, tail flicks, or soft vocalizations like chirps and growls. These are all completely normal signs of a healthy sleep cycle.
As cats transition into deeper sleep, their muscles relax suddenly, which can also cause brief jerks or spasms. These are similar to the hypnic jerks you might experience yourself when you’re falling asleep and your leg kicks or your body jolts. They’re isolated, last a second or two, and your cat stays relaxed through them.
The key characteristics of normal sleep twitching: the movements are small, brief, and affect one area at a time (a paw, the whiskers, the tail). Your cat’s body remains loose and relaxed overall. And if you gently say their name or touch them, they wake up normally, perhaps a little groggy but otherwise fine.
How to Tell It’s Not a Seizure
This is the concern most people have when they search this question, so here’s the distinction. Normal sleep twitches are small and localized. Seizures tend to be more intense, prolonged, and involve larger muscle groups or the whole body. A cat having a seizure may become rigid, paddle its legs rhythmically, drool heavily, or lose bladder control.
Focal seizures in cats can be subtler. They often involve orofacial automatisms: repetitive lip smacking, chewing, licking, swallowing, or facial twitching. These movements are more rhythmic and sustained than the random little jerks of dreaming. A cat in a seizure also typically cannot be woken up or redirected. If you call their name or touch them during normal sleep twitching, they’ll rouse. A seizing cat won’t respond, and when the episode ends, they may seem disoriented, lethargic, or confused for minutes to hours afterward.
If you’re unsure, try recording the episode on your phone. A short video is one of the most useful things you can bring to a vet appointment, since tremors and seizures rarely happen on command in the exam room.
Shivering From Cold or Fever
Cats maintain a normal body temperature between 100.0°F and 102.5°F (37.7°C to 39.2°C). If their body temperature drops below 99°F (37.2°C), they’re hypothermic and will shiver to generate warmth, just as you would. This is more common in very young kittens, elderly cats, thin cats, or cats that have been in a cold environment. A hypothermic cat will also appear lethargic and less alert than usual.
Fever causes shivering through a different mechanism. When a cat has an infection or inflammation, the brain’s internal thermostat resets to a higher target temperature. The body then “thinks” it’s too cold relative to that new set point, so it triggers shivering, blood vessel constriction, and piloerection (fur standing on end) to generate and conserve heat. A cat with a fever above 104°F (40°C) needs veterinary attention promptly. You can’t reliably detect a fever by touching your cat’s ears or nose. A rectal thermometer is the only accurate method at home.
Pain Can Cause Trembling at Rest
Cats are famously good at hiding pain, but their bodies sometimes give them away during rest, when they’re not actively compensating. Osteoarthritis is one of the most common causes of pain-related trembling, particularly in older cats. You might notice trembling in the hind legs when your cat is resting or standing still. Other signs of chronic pain include reluctance to jump, stiffness after lying down, decreased grooming, or changes in temperament.
Dental pain, abdominal discomfort, and urinary issues can also produce trembling or tension in a resting cat. If the shivering happens consistently while your cat is awake and at rest (not just during sleep), pain is worth investigating.
Low Blood Sugar in Kittens
Kittens are especially vulnerable to hypoglycemia, or low blood sugar. Their small bodies don’t store much energy, and stress factors like poor nutrition, cold environments, intestinal parasites, or skipping meals can deplete their reserves quickly. A hypoglycemic kitten may shiver, become lethargic, feel limp, or in severe cases, lose consciousness.
Adult cats can also develop low blood sugar, though it’s less common. Cats being treated for diabetes are at the highest risk, since insulin can sometimes lower blood sugar too far. Severe liver disease and certain rare pancreatic tumors are other potential causes. If your kitten is shivering and seems weak or unresponsive, this is an urgent situation.
Toxin Exposure
Certain household chemicals and medications can cause tremors in cats. One of the most well-documented is permethrin, an insecticide commonly found in flea treatments designed for dogs. Cats are highly sensitive to it, and exposure causes muscle tremors, twitching, and shivering in 10 to 58% of affected cats, often progressing to seizures. Symptoms usually appear within a few hours of exposure but can be delayed up to 72 hours.
Other substances that can cause tremors include lead, certain rodent poisons (particularly bromethalin-based products), human cold medications containing pseudoephedrine, and tremorgenic mycotoxins found in moldy food. If your cat’s shivering started suddenly and you suspect they may have gotten into something, bring the product packaging with you to the vet if possible.
Signs That Warrant a Vet Visit
Occasional twitching during sleep, in an otherwise healthy cat that eats well, plays normally, and wakes up fine, is almost always just dreaming. But you should pay attention if the shivering is accompanied by any of these:
- Not eating for more than 24 hours
- Vomiting, especially clear foamy fluid or bile
- Straining in the litter box or producing less urine than usual (lack of urination is a life-threatening emergency)
- Changes in gum color: pale gums may indicate anemia, yellow gums suggest liver problems, and bluish gums signal oxygen deprivation
- Breathing difficulties or open-mouth breathing
- Inability to wake your cat during an episode, or prolonged confusion afterward
- Stiffness, rigidity, or rhythmic full-body movements during the episode
If your vet suspects a neurological issue, they’ll likely start with blood work to check for metabolic problems, infections, or toxin exposure. A neurologic exam evaluates your cat’s mental alertness, reflexes, gait, and response to touch. More advanced testing, like imaging or cerebrospinal fluid analysis, is reserved for cases where initial results point toward a brain or spinal cord problem. For most cats whose owners notice sleep twitching, none of this turns out to be necessary.