What are the signs of a seizure in dogs?

Seizures have three phases. Pre-ictal (aura): anxiety, restlessness, hiding, or attention-seeking minutes before. Ictal (the seizure itself): muscle rigidity, paddling, jaw chomping, salivation, loss of consciousness, loss of bladder/bowel control — typically 1–3 minutes. Post-ictal (recovery): confusion, disorientation, temporary blindness, excessive thirst or hunger, profound tiredness — can last minutes to hours.

What is phenobarbital and how does it work in dogs?

Phenobarbital is the most commonly used anti-seizure medication for dogs. It works by enhancing GABA (an inhibitory neurotransmitter), reducing the frequency and intensity of seizures. It's given twice daily. The therapeutic serum level is 20–40 μg/mL. It takes 2 weeks to reach steady state, so a level check 2 weeks after starting or after a dose change is standard.

Can epilepsy be cured in dogs?

Idiopathic epilepsy cannot be cured — it's managed with lifelong medication. The goal is to reduce seizure frequency and severity to an acceptable level, not necessarily complete elimination. Many dogs achieve good seizure control and a normal quality of life on phenobarbital alone or in combination with other drugs. Secondary epilepsy caused by a treatable underlying condition may improve with that condition's treatment.

What is the life expectancy of a dog with epilepsy?

Dogs with well-controlled idiopathic epilepsy often live a normal lifespan. Dogs with poorly controlled epilepsy, status epilepticus, or seizures caused by brain tumors have a more guarded prognosis. Early diagnosis, consistent medication, and regular bloodwork monitoring all improve outcomes significantly.

Epilepsy in Dogs: Seizures, Diagnosis & Phenobarbital Monitoring

Q: When is a dog seizure an emergency?

Go to emergency immediately if: a single seizure lasts more than 5 minutes (status epilepticus), your dog has 2 or more seizures within 24 hours (cluster seizures), your dog doesn't return to normal within 30 minutes post-seizure, or this is the very first seizure. Status epilepticus is life-threatening and requires IV diazepam urgently.

Q: What bloodwork is needed for a dog with seizures?

Before starting treatment, your vet will run a full chemistry panel (glucose, BUN, creatinine, liver enzymes, electrolytes), CBC, bile acids, and urinalysis to rule out metabolic causes of seizures. Once on phenobarbital, liver enzymes (ALP, ALT, GGT) and serum phenobarbital levels are checked every 6 months for life.

Q: Does phenobarbital damage a dog's liver?

Phenobarbital commonly causes elevated liver enzymes (especially ALP and ALT) — this is an expected effect and doesn't always mean liver damage. However, a small percentage of dogs develop true hepatotoxicity over years of use. This is why liver panels must be checked every 6 months. If liver values climb significantly, dose adjustment or switching to a different drug may be needed.

Q: What is the normal phenobarbital level in dogs?

The therapeutic range for phenobarbital in dogs is 20–40 μg/mL (some labs report 15–45 μg/mL). Below 20 μg/mL is often subtherapeutic and seizures may break through. Above 40 μg/mL increases risk of sedation and liver toxicity. Blood for phenobarbital levels should be drawn just before a dose (trough level).

Q: What breeds are prone to epilepsy?

Breeds with higher genetic epilepsy risk include Border Collies, Australian Shepherds, Labrador Retrievers, Golden Retrievers, German Shepherds, Beagles, Belgian Tervurens, and Dachshunds. Idiopathic epilepsy typically first appears between 1 and 5 years of age. Seizures starting before 1 year or after 5 years are more likely secondary (structural or metabolic).

Quick Answer: Epilepsy in Dogs

Epilepsy is the most common neurological condition in dogs. Idiopathic epilepsy (genetic, no identifiable cause) affects dogs aged 1–5 years and is managed — not cured — with lifelong medication. Dogs on phenobarbital require liver panel and drug level checks every 6 months for life, making bloodwork monitoring a permanent part of their care.

Watching your dog have a seizure is terrifying. This guide covers what's actually happening, when to go to emergency, what your vet is looking for in bloodwork, and what long-term treatment and monitoring looks like.

Has your dog just been diagnosed or started phenobarbital?

Upload the pre-treatment bloodwork or most recent monitoring panel to track ALP, ALT, and GGT over time — the three values that matter most on long-term phenobarbital.

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Types of Seizures in Dogs

Not all seizures look the same, and the type matters for diagnosis:

Generalized (Grand Mal)

Affects the whole body. Loss of consciousness, muscle rigidity, paddling, jaw chomping, salivation, loss of bladder/bowel control. The classic image most people have of a seizure.

Focal (Partial)

Affects one body part or one side. Facial twitching, rhythmic blinking, one limb paddling, or "fly-biting" behavior. Dog may remain conscious. Can progress to generalized.

Cluster Seizures

Two or more seizures within 24 hours. Serious — the brain doesn't fully recover between events. Requires emergency care and often IV medication.

Status Epilepticus

A single seizure lasting more than 5 minutes, or seizures without recovery between them. Life-threatening emergency. Brain damage and death can occur without immediate IV treatment.

Warning

Emergency Thresholds — Go Now

• Seizure lasting more than 5 minutes
• 2 or more seizures in 24 hours (cluster)
• Dog not recovering to normal within 30–60 minutes post-seizure
• First seizure ever — always warrants same-day evaluation

What a Seizure Looks Like: The Three Phases

1. Pre-ictal (Aura) — minutes before the seizure
Anxiety, restlessness, hiding, clinginess, or staring blankly. Some owners learn to recognize this phase and can move their dog somewhere safe.
2. Ictal (The Seizure) — typically 1–3 minutes
Muscle rigidity, paddling, jaw chomping, hypersalivation, loss of consciousness, urination or defecation. Time the seizure if you can — this information is critical for your vet.
3. Post-ictal (Recovery) — minutes to hours
Confusion, disorientation, temporary blindness or deafness, profound fatigue, increased thirst or hunger. The dog is not in danger during this phase — keep them calm and prevent them from walking into walls or falling down stairs.

Causes of Seizures in Dogs

The first job is figuring out why the seizure happened. There are three broad categories:

Idiopathic (Primary) Epilepsy

No identifiable cause — presumed genetic. Most common. Typically first appears at 1–5 years of age. Diagnosed by ruling out structural and metabolic causes. Bloodwork, MRI, and CSF are normal.

Structural (Secondary) Epilepsy

Caused by a brain abnormality — tumor, encephalitis, head trauma, vascular event, or malformation. More likely if seizures start before age 1 or after age 5, if neurological deficits are present between seizures, or if seizures are focal. Requires MRI and CSF analysis.

Reactive (Metabolic) Seizures

The brain reacts to a systemic problem — hypoglycemia, liver disease (hepatic encephalopathy), severe electrolyte abnormalities, toxin ingestion, or kidney failure. Bloodwork finds the cause. Treat the underlying condition and seizures typically resolve.

Note

Age at First Seizure Is a Key Clue

Idiopathic epilepsy: 1–5 years old, normal exam, normal bloodwork.
Before 1 year: congenital abnormality or portosystemic shunt.
After 5 years: brain tumor, encephalitis, or metabolic disease until proven otherwise.

Bloodwork: What Your Vet Is Looking For

A full metabolic workup is required before any epilepsy diagnosis and before starting medication. The goal is to rule out reactive causes:

Glucose

Hypoglycemia causes seizures — especially in small breeds and puppies

BUN + Creatinine

Kidney failure can cause uremic encephalopathy and seizures

ALP + ALT + GGT

Liver disease causes hepatic encephalopathy; also baseline before phenobarbital

Bile acids

Screens for portosystemic shunt — a common cause of seizures in young dogs

Electrolytes (Na, K, Ca)

Severe imbalances can trigger seizures

CBC

Infection, anemia, or abnormal cells can point to systemic disease

Urinalysis

Supports kidney and liver assessment

Test	Why It's Checked
Glucose	Hypoglycemia causes seizures — especially in small breeds and puppies
BUN + Creatinine	Kidney failure can cause uremic encephalopathy and seizures
ALP + ALT + GGT	Liver disease causes hepatic encephalopathy; also establishes baseline before phenobarbital
Bile acids (pre/post-prandial)	Screens for portosystemic shunt — a common cause of seizures in young dogs
Electrolytes (Na, K, Ca)	Severe imbalances (especially low calcium or sodium) can trigger seizures
CBC	Infection, anemia, or abnormal cells can point to systemic cause
Urinalysis	Supports kidney and liver assessment; ammonium biurate crystals suggest liver shunt

Keep your dog's pre-treatment and monitoring results in one place

Upload your dog's bloodwork to VetLens and track liver enzymes and kidney values across every monitoring appointment. See which values are trending up before they become a problem.

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Treatment: Phenobarbital and Other Options

Not every dog with a seizure needs medication. Most neurologists recommend starting treatment when a dog has had 2 or more seizures in 6 months, cluster seizures, status epilepticus, or post-ictal periods longer than 24 hours.

Phenobarbital

First-line

Most effective and most studied anti-seizure drug for dogs. Given twice daily. Therapeutic range: 20–40 μg/mL. Reaches steady state in ~2 weeks — check serum level then. Side effects: initial sedation and increased thirst/urination/appetite (usually temporary). Long-term risk: liver toxicity, requiring regular monitoring.

Potassium Bromide (KBr)

Add-on or alternative

Often added when phenobarbital alone doesn't control seizures. Takes 3–4 months to reach steady state. Serum bromide levels are monitored. Side effects: sedation, hind limb weakness (bromide toxicity at high levels). Cannot be used in cats.

Levetiracetam (Keppra)

Newer option

Fewer drug interactions, minimal liver effects, no routine bloodwork monitoring beyond standard safety checks. Downside: short half-life in dogs requires dosing three times daily (extended-release formula reduces this). Often used with phenobarbital or as a single drug in dogs with liver concerns.

Zonisamide

Newer option

Twice-daily dosing, generally well tolerated. Can be used alone or with phenobarbital. Monitoring includes kidney function and liver enzymes. Useful when KBr side effects are a concern.

Monitoring Schedule for Dogs on Phenobarbital

This is the part most owners aren't prepared for: epilepsy management means repeat bloodwork, indefinitely. Here's the standard schedule:

Before starting

Full chemistry, CBC, bile acids, urinalysis — baseline and metabolic rule-out

2 weeks after starting

Serum phenobarbital level (trough — draw just before a dose)

6 months

Serum phenobarbital level + full chemistry (ALP, ALT, GGT, BUN, creatinine)

Every 6 months ongoing

Same as above for life

After any dose change

Serum phenobarbital level at 2 weeks post-change

Timepoint	Tests
Before starting	Full chemistry, CBC, bile acids, urinalysis — baseline and metabolic rule-out
2 weeks after starting	Serum phenobarbital level (trough — draw just before a dose)
6 months	Phenobarbital level + full chemistry (ALP, ALT, GGT, BUN, creatinine)
Every 6 months ongoing	Same as above — for life
After any dose change	Serum phenobarbital level 2 weeks post-change

Warning

Phenobarbital and Liver Enzymes

Phenobarbital reliably raises ALP and ALT — this is an expected drug effect and does not automatically mean liver damage. However, if enzymes climb very high (ALT >5× normal) or GGT rises significantly, your vet may reduce the dose or switch medications.

This is why tracking trends across multiple panels matters. A single elevated ALP is ambiguous — a doubling trend over 12 months is a signal to act on.

Breeds at Higher Risk

Higher Genetic Risk

• Border Collie
• Australian Shepherd
• Belgian Tervuren
• Labrador Retriever
• Golden Retriever
• German Shepherd
• Beagle
• Dachshund

Key Diagnostic Clues by Breed

• Yorkshire Terrier, Maltese: consider liver shunt first (especially <2 years)
• Boxer, Boston Terrier: brain tumor common (>5 years)
• Cavalier King Charles: syringomyelia and structural brain abnormalities
• Any small breed puppy: hypoglycemia until ruled out

At-Home Seizure Management

• Keep a seizure diary. Date, time, duration, type, and recovery time. This is the most useful information you can bring your vet.
• Time every seizure. It's hard to judge duration in the moment — set a timer when it starts.
• Don't put your hand near the mouth. Dogs cannot swallow their tongue. Your hand can be injured.
• Move hazards away. Protect from falls and sharp objects. Use a rolled blanket to cushion the head.
• Stay calm and quiet. Dim lights, reduce noise during recovery.
• Never stop phenobarbital abruptly. Sudden discontinuation triggers severe rebound seizures. Always taper under veterinary guidance.

Questions About Your Dog's Seizure Medication?

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Good News

Key Takeaway

Most dogs with idiopathic epilepsy live a good quality of life on medication. The difference between well-managed and poorly managed epilepsy is usually consistency — consistent medication timing, consistent monitoring, and consistent seizure logging.

Phenobarbital works well but requires liver panels every 6 months for life. Don't skip these. The goal is catching a trend before it becomes a crisis.

Track Your Dog's Phenobarbital Monitoring

Upload each monitoring panel to VetLens and see:

✓ ALP, ALT, GGT trends over every appointment
✓ Kidney values to catch early drug effects
✓ Side-by-side comparison of pre-treatment vs current values
✓ Plain-language explanation of what each change means

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Frequently Asked Questions

What is epilepsy in dogs?

Epilepsy is a neurological condition causing recurrent seizures. Idiopathic (genetic) epilepsy is the most common form, typically appearing in dogs aged 1–5 years with no identifiable structural cause. It's managed with lifelong medication, not cured.

When is a dog seizure an emergency?

Go to emergency immediately if a seizure lasts more than 5 minutes (status epilepticus), if your dog has 2+ seizures in 24 hours (cluster), if they don't recover normally within 30–60 minutes, or if it's a first seizure. Status epilepticus is life-threatening without IV treatment.

What bloodwork does a dog with epilepsy need?

Before treatment: full chemistry panel, CBC, bile acids, and urinalysis to rule out metabolic causes. Once on phenobarbital: serum drug level at 2 weeks, then liver enzymes (ALP, ALT, GGT) and phenobarbital level every 6 months for life.

What is the normal phenobarbital level in dogs?

The therapeutic range is 20–40 μg/mL. Below 20 μg/mL is often subtherapeutic and breakthrough seizures are more likely. Above 40 μg/mL increases sedation and liver toxicity risk. Blood should be drawn as a trough level — just before a scheduled dose.

Does phenobarbital damage a dog's liver?

Phenobarbital routinely raises ALP and ALT — this is an expected drug effect, not automatically liver damage. However, a small percentage of dogs develop true hepatotoxicity over years of use. Regular 6-month liver panels catch this early. If enzymes climb significantly, dose adjustment or switching drugs may be needed.

Can I stop phenobarbital if my dog hasn't had a seizure?

Never stop phenobarbital abruptly — sudden discontinuation triggers severe rebound seizures that can be life-threatening. If you want to trial stopping medication, it must be done gradually over weeks under veterinary supervision, and only after a prolonged seizure-free period.

What breeds are prone to epilepsy?

Breeds with higher genetic risk include Border Collies, Australian Shepherds, Labrador Retrievers, Golden Retrievers, German Shepherds, Belgian Tervurens, Beagles, and Dachshunds. Idiopathic epilepsy typically first appears between ages 1 and 5.