CBD for Dogs With Seizures: What the Research Actually Shows

Every controlled trial published on CBD for dogs with seizures has found the same direction of result. Dogs given CBD alongside their existing anti-seizure medication had fewer seizures than on placebo. An independent 2025 systematic review by Jensen and colleagues confirmed that consistency across every randomized controlled trial it assessed. What the same body of research also shows is that the size of that effect varies enormously between individual dogs, and that liver enzymes rose in every study.

Across all four published veterinary trials, dogs given CBD alongside conventional anti-seizure medication had fewer seizures than on placebo, though how much any individual dog improves varies widely and liver enzyme activity rose consistently.

Let's be real for a second. If you are reading this, you have probably already watched your dog seize. You know the sound. You know the sixty seconds afterward where you do not know what to do with your hands.

You have also almost certainly read a page that opened with "89% of dogs had fewer seizures" and closed with a buy button. I want to give you the whole picture instead. The good news is real. So are the things you need to watch.

What does the research on CBD for dogs with seizures actually show?

Idiopathic epilepsy, meaning seizures with no identifiable underlying cause, affects up to 5.7% of dogs worldwide and is the most common canine neurological condition. Roughly 30% of those dogs keep seizing despite being on anti-seizure medication. That gap is why this research exists at all.

Four trials have now been published. Every one of them gave CBD in addition to the dog's existing anti-seizure medication, never instead of it. And every one of them found seizure frequency went down.

The strongest single result in that table is the Florida trial from 2022. Fourteen dogs with hard-to-control epilepsy, crossover design, so every dog acted as its own control. Seizure frequency fell from an average of eight events to five. Seizure days fell from around six to four. Both results were statistically significant. And six of the fourteen dogs halved their seizure activity on the extract, while none of them managed that on placebo. Adverse effects were mild and no more common than on placebo.

That is the clearest positive finding we have, and it is worth knowing that the product tested was a CBD and CBDA-rich hemp extract rather than CBD alone.

What does "89% of dogs improved" actually mean?

The famous number comes from a 2019 Colorado State University trial led by Dr. Stephanie McGrath, published in the Journal of the American Veterinary Medical Association. Twenty-six dogs with hard-to-control idiopathic epilepsy were randomly assigned to CBD-infused oil or plain oil for 12 weeks, on top of their existing medication.

The CBD group's seizure frequency fell by a median of 33% compared with placebo, and that result was statistically significant. The more CBD measured in a dog's blood, the bigger that dog's reduction. That dose-response relationship is one of the most encouraging things in the whole literature, because it suggests the effect is real rather than coincidental.

Here is the piece that gets left off, and it is not a reason to dismiss the finding. It is a reason to read it correctly. In the same paper, the proportion of dogs who counted as responders, meaning a 50% or greater drop, was similar between the CBD group and the placebo group. What that tells you is that the average came down, but it came down because some dogs improved a lot rather than because most dogs improved a little.

So "89% of dogs improved" and "my dog will improve" are different statements. Some dogs respond well. Predicting which dogs is exactly what the research has not cracked yet.

The 2023 follow-up is the largest trial we have and it points the same way. Fifty-one dogs, double-blinded, crossover. The first dose tested, 5 mg per kg per day, did so little it was abandoned after twelve dogs. At 9 mg per kg per day, seizure days fell 24.1% on CBD while rising 5.8% on placebo. Liver enzymes rose at both doses, and reduced appetite and vomiting were more common on CBD.

Here's what the research tells us overall. Jensen and colleagues, in their 2025 systematic review, looked at all three randomized controlled trials and found every one of them showed seizure frequency falling on CBD. It also rated all three at moderate to high risk of bias, noted that the published literature tends to emphasize the benefits and underplay the side effects, and called for larger, better-designed studies. Both halves of that are worth carrying with you.

Where is this research heading?

Forward, and faster than most supplement categories ever do.

The American Kennel Club Canine Health Foundation funded the 2023 Colorado State trial and has since funded a follow-up specifically to refine dosing and formulation. That is a serious, non-commercial research body putting money behind this question twice.

Colorado State has also moved on to a bigger question. They are now running a trial testing CBD as a primary therapy on its own, head-to-head against phenobarbital, in dogs not yet on any anti-seizure medication. Nobody designs that study around a compound they think does nothing.

So the honest position today is not "CBD does not work." It is "CBD does something measurable, we do not yet know the right dose, the right formulation, or which dogs it suits." Those answers are actively being worked on.

Is CBD safe alongside seizure medication?

This is the question that matters most, so let me answer it before anything else. Every trial above ran CBD alongside conventional anti-seizure medication, and none of them asked a dog to stop taking it. Nobody should. Stopping anti-seizure medication abruptly is dangerous, and that decision belongs to your vet and nobody else.

On interactions specifically, the news is reassuring. CBD is broken down in the liver and gut by cytochrome P450 enzymes, the same family that processes many anti-seizure drugs, so an interaction is plausible on paper. In practice, McGrath's team found no significant change in blood phenobarbital or bromide levels in dogs given CBD alongside them, and the 2022 Florida trial found the same for zonisamide, phenobarbital and bromide.

The liver enzyme finding is the consistent one, and it is the reason this is a vet conversation rather than a shopping decision. Alkaline phosphatase rose in every trial. The 2023 study recommends monitoring liver values in any dog given CBD, particularly one already on long-term medication. If your vet is already running routine bloodwork, you have a baseline to compare against, which puts you ahead of most.

What CBD dosage did the studies use?

I am giving you these so you can take real numbers into an appointment, not so you can dose at home. Every one of these was given under veterinary supervision with bloodwork alongside it.

1. McGrath 2019: 2.5 mg per kg of CBD oil by mouth, twice daily, for 12 weeks.
2. Garcia 2022: 2 mg per kg of a CBD and CBDA-rich hemp extract, twice daily, for 12 weeks.
3. Rozental 2023: 5 mg per kg per day was abandoned for lack of effect; 9 mg per kg per day was the dose that worked.
4. Exploratory 2025: a start-low, go-slow titration, individualized per dog rather than one fixed dose.

Notice the direction of travel. The doses that produced results are considerably higher than what most retail dosing charts suggest, and the lowest dose in the largest trial did nothing at all. If your dog has been on a small dose from a dropper chart and you concluded it does not work, that conclusion may say more about the dose than about CBD. That is a conversation for your vet, with these numbers in hand.

One more thing Dr. McGrath has said publicly, and I agree with her completely: the hemp market is loosely regulated, and product testing has repeatedly found bottles that do not contain what the label claims. Whatever you and your vet decide, ask for a current Certificate of Analysis. If a company cannot produce one, that is your answer.

What else is worth looking at, beyond the oil?

This is the part I care about most, because it is the part you control.

Look at what is already going into your dog. The FDA has issued a fact sheet on isoxazoline flea and tick products, the class that includes Bravecto, NexGard, Credelio, and Simparica. The agency considers the class safe and effective, and also states plainly that these products have been associated with neurological adverse reactions including muscle tremors, ataxia and seizures, and that seizures may occur in animals with no prior history. If your dog seizes and is on one of these, that is a conversation to have at the next appointment. We wrote more on that in flea and tick medication side effects in dogs.

Look at the liver. Long-term anti-seizure medication and CBD both lean on the same organ. Supporting it is not glamorous and it will not show up as fewer seizures next week, but it is the kind of quiet groundwork that matters over years. Our guide to natural liver support for dogs explains the difference between supporting an organ and the marketing word "detox."

Look at diet, and at ketones. There is a separate and arguably more interesting body of research on medium-chain triglycerides and canine epilepsy, and it does not have the same responder-rate problem. We covered it in detail in MCT oil for dogs with seizures. If you only read one more thing after this, read that one.

If you want the foundations laid out in order, rather than piece by piece across a dozen tabs at 2am, our free guide walks through the whole thing.

How do you know if it is helping?

Epilepsy is unpredictable, which makes it very easy to credit whatever you started last month for a quiet fortnight that was going to happen anyway. Given how much the response varies between dogs, tracking properly is the only way you will know whether yours is one of the ones who benefit. Here is what a fair test looks like.

1. Get a baseline first. The trials used a 12-week baseline before starting anything. Log at least eight weeks of seizure dates before you change one variable.
2. Count seizure days, not only seizures. A dog who clusters can have six events in one day. Researchers count both, because the two numbers move differently.
3. Change one thing at a time. Start the oil and switch the food in the same week and you will never know which did what.
4. Give it three months. Every trial above ran 12 weeks. Three quiet weeks is not evidence.
5. Recheck bloodwork. Liver values are the thing to watch, and they will not announce themselves.

Questions worth taking to your vet

Write these down and take them in. You are allowed to ask what else there is.

1. Is my dog's epilepsy considered drug-resistant, or have we not exhausted the conventional options yet?
2. Would you be comfortable with me adding CBD alongside her current medication, and at what dose?
3. The published trials used doses between 2 and 9 mg per kg per day. Where would you want to start?
4. How often would you want to recheck liver values if we did?
5. Are any of the products she is on, including flea and tick products, worth reviewing given the seizures?
6. Would you refer us to a veterinary neurologist, or to an integrative vet who works with both?

You are not being difficult by asking. You are doing exactly what a good vet wants you to do.

You are not alone, so many pet parents go through this. And you are not behind for wanting the real numbers before you spend another dollar. That instinct is the right one.

Much love, Larry

Sources

1. Jensen HA, Olsen A, Arendt M, Sandøe P, Nielsen SS. Cannabidiol treatment for refractory idiopathic epilepsy in dogs: a systematic review with risk of bias assessment. Preventive Veterinary Medicine, 2025.
2. McGrath S, Bartner LR, Rao S, Packer RA, Gustafson DL. Randomized blinded controlled clinical trial to assess the effect of oral cannabidiol administration in addition to conventional antiepileptic treatment on seizure frequency in dogs with intractable idiopathic epilepsy. Journal of the American Veterinary Medical Association, 2019.
3. Garcia GA, et al. Safety and efficacy of cannabidiol-cannabidiolic acid rich hemp extract in the treatment of refractory epileptic seizures in dogs. Frontiers in Veterinary Science, 2022.
4. Rozental AJ, Weisbeck BG, Corsato Alvarenga I, Gustafson DL, Kusick BR, Rao S, Bartner LR, McGrath S. The efficacy and safety of cannabidiol as adjunct treatment for drug-resistant idiopathic epilepsy in 51 dogs: a double-blinded crossover study. Journal of Veterinary Internal Medicine, 2023.
5. An Exploratory Study of Cannabidiol as an Adjunctive Treatment for Refractory Epilepsy in Dogs. Animals, 2025.
6. American Kennel Club Canine Health Foundation. Evidence for the Use of CBD to Treat Canine Idiopathic Epilepsy, 2024.
7. Colorado State University Veterinary Teaching Hospital. The use of cannabidiol as an alternative to standard anticonvulsant therapy in dogs with idiopathic epilepsy, clinical trial listing.
8. Colorado State University College of Veterinary Medicine and Biomedical Sciences. Results from CBD clinical trial on seizure frequency in dogs, 2019.
9. US Food and Drug Administration. Fact Sheet for Pet Owners and Veterinarians about Potential Adverse Events Associated with Isoxazoline Flea and Tick Products.
10. US Food and Drug Administration. What You Need to Know About Products Containing Cannabis or Cannabis-Derived Compounds, Including CBD.