Diagnosing seizures in dogs involves a layered process: your vet will start with blood work and a neurological exam to rule out metabolic causes, then move to brain imaging if needed. There’s no single test that confirms a seizure disorder. Instead, diagnosis works by elimination, ruling out other conditions until the most likely cause becomes clear.
Recognizing What a Seizure Looks Like
Before diagnosis can begin, you need to know what you’re looking at. Not all seizures involve full-body convulsions, and some are easy to miss entirely.
Generalized seizures are the most recognizable type. A dog suddenly falls over with violent jerking of all four limbs, paddling motions, frothing at the mouth, and possible loss of bladder or bowel control. The dog is unconscious during these events. Some generalized seizures look different: the dog may go stiff with rigid, extended limbs (tonic), or simply stand and stare without responding to anything (atonic).
Focal seizures are subtler and happen when abnormal electrical activity is limited to one area of the brain. These can look like repeated twitching of an eyelid, lip, or ear. One classic presentation is “fly-biting,” where the dog appears to see and snap at invisible flies. Another is the “chewing gum fit,” where the jaw repeatedly clacks. Dogs may remain fully conscious during focal seizures, which is why owners sometimes don’t realize what they’re witnessing.
What Your Vet Does First
The diagnostic workup starts with two things: a thorough physical and neurological examination, and baseline blood work. The neurological exam checks reflexes, coordination, gait, vision, and mental alertness. Any abnormalities between seizure episodes can point toward a structural brain problem rather than epilepsy.
Blood work is essential in every seizure case. A complete blood count and chemistry panel checks blood sugar, liver enzymes, kidney values, electrolytes, and protein levels. The goal is to identify metabolic problems that can trigger seizures without any brain disease being present. Low blood sugar, for instance, is a recognized seizure cause, especially if tied to an underlying condition like a tumor. Elevated ammonia levels can indicate liver dysfunction causing a condition called hepatic encephalopathy. High creatinine and urea point toward kidney disease. A urinalysis and thyroid level check round out the initial screening.
If the vet suspects a liver problem, they may add fasting and post-meal bile acid tests. If toxin exposure is a possibility, cholinesterase activity (a marker of certain poisonings) can be measured.
What You Should Record at Home
Your observations are a critical diagnostic tool because vets rarely witness the seizure themselves. Keep a seizure diary that includes the date, how long the episode lasted, what the dog’s body did during it, and whether anything seemed to trigger it. Note whether your dog lost consciousness, urinated, salivated heavily, or had muscle jerking on one side versus both.
Pay attention to what happens afterward, too. The post-ictal period, the recovery window after a seizure, can involve disorientation, confusion, pacing, temporary blindness, or excessive thirst. This phase typically lasts less than 24 hours, and the details help your vet classify the seizure type and severity. Video from your phone is extremely useful if you can safely capture it.
When Advanced Imaging Is Needed
If blood work comes back normal and seizures continue, the next step is brain imaging with an MRI and possibly a cerebrospinal fluid (CSF) analysis. These tests look for structural causes like brain tumors, inflammation, or infection.
Not every dog needs an MRI after a first seizure. But it becomes more important when the neurological exam reveals abnormalities between episodes, when the dog is younger than six months or older than six years at first seizure onset, or when seizures are worsening in frequency or severity. Dogs with abnormal neurological exams are nine times more likely to have CSF results that change their treatment plan, so the test carries more weight in those cases.
When the MRI and CSF come back normal in a dog with recurrent seizures, that actually supports a diagnosis of idiopathic epilepsy, the most common seizure disorder in dogs. The absence of findings is itself informative.
How Idiopathic Epilepsy Is Diagnosed
Idiopathic epilepsy, meaning epilepsy with no identifiable structural or metabolic cause, is the most common diagnosis in dogs with recurring seizures. It’s diagnosed through a tiered confidence system developed by the International Veterinary Epilepsy Task Force.
The first tier requires a history of two or more unprovoked seizures occurring at least 24 hours apart, seizure onset between six months and six years of age, a normal neurological exam between episodes, and normal baseline blood work and urinalysis. Many dogs are diagnosed and treated at this level.
The second tier adds normal bile acid tests, a clean brain MRI, and unremarkable CSF analysis on top of the first-tier criteria. This gives a higher level of diagnostic confidence. A third tier exists that involves electroencephalography (EEG), measuring the brain’s electrical activity directly, though this is rarely performed outside of specialty or research settings.
Seizures vs. Fainting
One important distinction your vet will consider is whether your dog actually had a seizure or fainted. Fainting episodes (syncope) can look similar at first glance, but the differences matter because the causes and treatments are completely different. Dogs that faint typically go limp and recover within seconds, returning to normal almost immediately. Dogs that seize are more likely to have rigid or jerking muscles, may lose bladder control, and usually go through a prolonged recovery period of confusion or disorientation. Fainting often has a cardiac cause, so your vet may recommend a heart workup if the episode doesn’t fit the seizure pattern.
Emergency Situations
Two scenarios require immediate veterinary attention rather than a scheduled workup. Status epilepticus is a seizure lasting more than five minutes, or two or more seizures without the dog fully regaining consciousness between them. Cluster seizures are two or more seizures within a 24-hour period where the dog does regain consciousness in between. Both situations can cause brain damage and need urgent intervention. If your dog’s seizure passes the five-minute mark, that’s the threshold for an emergency visit.