The most common reason dogs have repeated seizures is idiopathic epilepsy, a condition where the brain produces abnormal electrical activity without any identifiable underlying disease. The majority of dogs with epilepsy have their first seizure between ages 1 and 5, and dogs in that age range are the most likely to receive an idiopathic epilepsy diagnosis. But about one-third of dogs in that same age group turn out to have a structural or metabolic cause instead, so repeated seizures always warrant a veterinary workup.
What a Seizure Looks Like in Three Stages
A seizure isn’t just the dramatic convulsing part. It unfolds in three distinct phases, and recognizing all of them helps you track what’s happening and report useful details to your vet.
The first stage is the pre-ictal phase, sometimes called the “aura.” Your dog may act restless, clingy, or unusually anxious in the minutes before a seizure begins. Not every dog shows obvious warning signs, but if yours does, you’ll likely start recognizing the pattern over time.
The seizure itself is the ictal phase. A dog in a full (generalized) seizure suddenly falls over with violent jerking spasms in all four limbs, paddling motions, frothing at the mouth, and sometimes loss of bladder or bowel control. They’re typically unconscious during this, even if their eyes are open. Most seizures resolve on their own within one to two minutes.
Afterward comes the post-ictal phase, which can last minutes to hours. Your dog may seem disoriented, confused, temporarily blind, or even aggressive. This recovery period is normal, and the confusion will pass. Give your dog a quiet, safe space and avoid putting your hands near their mouth.
Idiopathic Epilepsy: The Most Common Cause
Idiopathic means “no known cause.” In these dogs, blood work, imaging, and other tests come back normal. The brain simply has a lower threshold for seizure activity, likely due to genetics. This is the single most frequent diagnosis in dogs who start seizing between ages 1 and 5.
Certain breeds carry a higher genetic risk. A large study of 35 breeds using Swedish veterinary records found that Boxers had the highest epilepsy incidence and mortality rate among the breeds analyzed. Other breeds commonly associated with idiopathic epilepsy include Labrador Retrievers, Golden Retrievers, German Shepherds, Beagles, and Belgian Tervurens, though the condition can appear in any breed or mixed-breed dog.
Idiopathic epilepsy is a lifelong condition. It’s managed rather than cured, but many dogs live full, normal lives with proper treatment.
Metabolic and Toxic Causes
When something outside the brain disrupts blood chemistry, seizures can follow. These are called reactive seizures because the brain itself is healthy but reacting to an abnormal internal environment.
Low blood sugar (hypoglycemia) is a common trigger, especially in puppies and toy breeds. In adult dogs, hypoglycemia typically results from insulin overdoses in diabetic dogs, liver shunts (where blood bypasses the liver and toxins build up), Addison’s disease, sepsis, or ingestion of xylitol, the sugar substitute found in many sugar-free gums and peanut butters. Liver disease on its own can also cause seizures because the liver is responsible for filtering toxins from the bloodstream. When it fails, those toxins reach the brain.
Kidney failure, severe electrolyte imbalances, and thyroid disorders can all produce recurring seizures as well. The good news is that metabolic causes are often identifiable through routine blood work, and treating the underlying condition can stop the seizures entirely.
Structural Brain Problems
If your dog’s seizures are caused by a physical abnormality in the brain, this is called structural epilepsy. Brain tumors, encephalitis (inflammation of the brain), strokes, and head trauma are the main culprits.
Brain tumors are a leading concern in dogs over 5 years old who begin seizing for the first time. Seizures, blindness, behavior changes, mental dullness, and circling are all signs of disease in the front part of the brain, which is where many tumors develop. Some brain tumors cause enough surrounding inflammation that they can mimic encephalitis on initial testing, so advanced imaging like an MRI is often needed to tell them apart.
Encephalitis can be caused by infections (viral, bacterial, fungal, or parasitic) or by the immune system attacking the brain’s own tissue. One form, necrotizing meningoencephalitis, is seen primarily in small breeds like Pugs, Maltese, and Chihuahuas, and seizures are a common feature. Encephalitis tends to progress if left untreated, so early diagnosis matters.
How Age Shapes the Diagnosis
Your dog’s age at the first seizure gives your vet a strong starting point for narrowing down the cause.
- Under 1 year: Congenital brain malformations, infections (like canine distemper), liver shunts, toxin exposure, and hypoglycemia are the most likely causes. Idiopathic epilepsy is less common in this group.
- 1 to 5 years: Idiopathic epilepsy is the leading diagnosis, though roughly one-third of dogs in this range have a structural or metabolic explanation instead.
- Over 5 years: Brain tumors become a primary concern, along with metabolic diseases that develop with age, such as liver or kidney failure. A dog who starts seizing after age 5 with no prior history is unlikely to have simple idiopathic epilepsy.
How Recurring Seizures Are Managed
If your dog has had a single, isolated seizure, your vet may recommend monitoring rather than immediate medication. But when seizures recur, especially more than once every few months, long-term anti-seizure medication is typically started. Phenobarbital and levetiracetam are the two most commonly prescribed options. Both require periodic blood tests to monitor levels and check for side effects on the liver.
Medication doesn’t eliminate seizures in every dog. The goal is to reduce how often they happen and how severe they are. Most dogs on medication still have an occasional breakthrough seizure, particularly during dose adjustments or periods of stress. Finding the right drug and dose can take weeks to months, and your vet may need to combine medications or switch approaches if the first option isn’t effective enough.
For dogs with metabolic or structural causes, treating the root problem is the priority. A dog seizing from low blood sugar needs blood sugar management. A dog with a brain tumor may benefit from surgery, radiation, or palliative medications depending on the tumor type and location.
When Seizures Become an Emergency
Most individual seizures, while frightening to watch, resolve on their own and aren’t immediately life-threatening. Two situations change that.
The first is status epilepticus: a seizure that lasts longer than five minutes without stopping on its own. This is a medical emergency because prolonged seizure activity can cause brain damage, dangerously high body temperature, and organ failure. If your dog is seizing and the five-minute mark passes, get to an emergency vet immediately.
The second is cluster seizures: multiple seizures within a 24-hour period, even if your dog seems to recover between them. Cluster seizures tend to escalate, and dogs who experience them once are likely to have them again. Your vet may prescribe an at-home rescue medication you can administer rectally or nasally to break a cluster before it becomes status epilepticus.
What to Track Between Vet Visits
Keeping a seizure log is one of the most useful things you can do. Record the date, time of day, duration, and what the seizure looked like (full body vs. one-sided, paddling vs. stiffening). Note anything unusual that happened beforehand: a missed meal, a new treat, exposure to chemicals, or an unusually stressful event. This information helps your vet identify patterns, adjust medications, and decide whether further diagnostics are needed.
Video is even better than a written description. If you can safely grab your phone during a seizure, a short recording gives your vet far more detail than words alone. Just make sure your dog is in a safe position on the floor, away from stairs or furniture edges, before you start filming.