Seizures in cats stem from three broad categories of causes: problems inside the brain (tumors, infections, inflammation), problems elsewhere in the body that affect the brain (liver disease, low blood sugar, toxin exposure), and idiopathic epilepsy, where no underlying cause can be found. Unlike dogs, where epilepsy with no known cause is the most common diagnosis, cats with seizures are more likely to have an identifiable underlying condition driving the episodes.
What a Cat Seizure Looks Like
Cat seizures don’t always look like the dramatic, full-body convulsions most people picture. In fact, cats frequently have focal seizures, meaning only part of the brain is misfiring. During a focal seizure, a cat may freeze in place, twitch one side of the face, drool, or display odd repetitive movements. Some cats become unusually restless or pace without purpose. These episodes can be subtle enough that owners mistake them for quirky behavior.
Focal seizures can also spread to become generalized seizures, where the cat loses consciousness, falls on its side, and experiences stiffening or rhythmic jerking of the whole body. Because the focal phase at the start is often brief, many of these look like they began as full-body events from the outset. Without specialized brain monitoring, the initial focal component frequently goes unrecognized.
After a seizure ends, cats enter a recovery period called the post-ictal phase. During this time your cat may seem disoriented, excessively sleepy, restless, or unusually clingy or withdrawn. This phase can last anywhere from a few hours to a full 24 to 48 hours, which can be alarming if you’re not expecting it.
Toxins and Household Chemicals
Poisoning is one of the most common and most preventable causes of seizures in cats. Cats have unusual liver metabolism that makes them far less efficient at breaking down certain chemicals compared to dogs or humans. Substances that might cause only mild symptoms in a dog can be life-threatening in a cat.
Pyrethrin and pyrethroid insecticides are a major culprit. These chemicals, derived from chrysanthemum flowers (or their synthetic versions), are found in flea shampoos, topical flea-and-tick spot-on treatments, yard sprays, indoor foggers, and granular garden products. Dog-specific flea treatments containing pyrethrins or pyrethroids are especially dangerous. A well-meaning owner applying a dog flea product to a cat, or even letting a cat cuddle with a recently treated dog, can trigger serious toxicity including seizures.
Other common toxins that can cause feline seizures include certain essential oils (especially tea tree oil), rodent poisons, antifreeze (ethylene glycol), and some human medications like antidepressants or ADHD drugs that a cat might accidentally ingest.
Metabolic and Organ-Related Causes
When organs outside the brain aren’t functioning properly, the chemical imbalances they create can trigger seizures. The liver is a frequent offender. Cats born with a portosystemic shunt, an abnormal blood vessel that routes blood around the liver instead of through it, can develop a condition called hepatic encephalopathy. Toxins that the liver would normally filter, especially ammonia from digested food, build up in the bloodstream and poison the brain. These shunts also cause low blood sugar and low protein levels because the liver plays a central role in maintaining both.
Low blood sugar (hypoglycemia) from other causes can also trigger seizures. This sometimes occurs in cats with insulin-producing tumors of the pancreas or in diabetic cats receiving too much insulin. Electrolyte imbalances, particularly low potassium or low sodium, are additional metabolic triggers. Kidney disease, which is common in older cats, can contribute to seizure activity when waste products accumulate in the blood.
Brain Tumors
Meningioma is the most common primary brain tumor in cats. It grows from the membranes surrounding the brain and tends to appear in middle-aged to older cats. New-onset seizures are the single most common reason these tumors get discovered. A cat that has never had a seizure before and suddenly starts having them after age 7 warrants serious investigation for a structural brain problem.
Research shows that structural causes like tumors are more likely than idiopathic epilepsy when seizures first appear in older cats, when a cat shows neurological abnormalities between seizure episodes, or when seizures escalate to prolonged or repeated events. The location of the tumor in the brain determines the specific symptoms. Forebrain tumors, the ones most associated with seizures, may also cause behavioral changes, circling, or vision problems.
Infections and Brain Inflammation
Several infectious diseases can invade a cat’s brain and trigger seizures. Feline infectious peritonitis (FIP) is one of the most serious. The virus infects certain white blood cells that then travel throughout the body, including into the brain and the membranes surrounding it. Once there, it causes intense inflammation and granuloma-like lesions. Neurological signs of FIP can include seizures, tremors, difficulty walking, behavioral changes, and involuntary eye movements.
Toxoplasmosis, caused by a parasite most cats pick up from hunting or eating raw meat, can also affect the brain and cause seizures, particularly in cats with weakened immune systems. Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) don’t always cause seizures directly, but they suppress the immune system and make cats vulnerable to secondary brain infections that do.
Idiopathic Epilepsy
When every test comes back normal and no structural, metabolic, or toxic cause can be found, the diagnosis is idiopathic epilepsy. This means the brain is producing seizures on its own without an identifiable trigger. Studies estimate that 22% to 59% of adult cats with seizures fall into this category, a wide range that reflects how thoroughly each cat was tested.
Idiopathic epilepsy is far less common in cats than in dogs. In dogs, it’s the leading cause of seizures and frequently has a genetic basis across many breeds. In cats, a genetic predisposition has rarely been documented. This is actually important context: if your cat is having seizures, the odds are higher that something specific is causing them, which makes thorough diagnostic testing especially worthwhile.
How Veterinarians Find the Cause
The diagnostic process typically starts with blood work and a urinalysis to screen for metabolic problems like liver disease, kidney failure, low blood sugar, or electrolyte imbalances. A bile acid test, which measures how well the liver is processing blood, helps identify portosystemic shunts. Cats are also commonly tested for FeLV, FIV, FIP, and toxoplasmosis through blood tests.
If blood work doesn’t reveal a cause, the next step is brain imaging, usually an MRI. This is the best tool for detecting tumors, areas of inflammation, or structural abnormalities in the brain. After the MRI, veterinarians often collect a sample of cerebrospinal fluid (the liquid surrounding the brain and spinal cord) to check for signs of infection or inflammation that imaging alone might not reveal.
Your cat’s age and the pattern of seizures help guide where vets look first. A young cat with seizures might be evaluated for a liver shunt or infection. An older cat with new seizures and neurological signs between episodes points strongly toward a structural problem like a tumor. Cats with normal neurological exams between seizures and normal blood work are more likely to receive an idiopathic epilepsy diagnosis, though MRI is still recommended to rule out subtle brain lesions.
When Seizures Become an Emergency
A single, brief seizure that resolves on its own is frightening but not necessarily an emergency in the immediate moment. Two situations, however, require urgent veterinary care. Cluster seizures, defined as two or more seizures within a 24-hour period, signal that the brain’s seizure threshold has dropped dangerously low. Status epilepticus is even more critical: continuous seizure activity lasting longer than 5 minutes, or multiple seizures back to back without the cat fully regaining consciousness over a span of 30 minutes or more.
Cats in status epilepticus showed abnormal neurological findings 100% of the time in one study, compared to about 38% of cats with single generalized seizures. Blood test abnormalities were also more frequent. Status epilepticus is more commonly linked to structural brain disease than to idiopathic epilepsy, and it carries significant risks of permanent brain damage or death without immediate treatment.