It depends on what you mean by “hemp oil.” Plain hemp seed oil, the kind sold as a cooking oil or nutritional supplement, contains no compounds that reduce seizures. What does show promise is CBD oil extracted from the hemp plant. Early clinical trials in dogs are encouraging, with one Colorado State University study finding that 89 percent of dogs given CBD experienced fewer seizures. But the evidence is still limited, the results are mixed across studies, and no CBD product is FDA-approved for use in animals.
Hemp Seed Oil and CBD Oil Are Not the Same
This is the single most important distinction for dog owners to understand. Hemp seed oil is pressed from hemp seeds and contains healthy fatty acids but virtually no CBD or other active cannabinoids. It will not help with seizures. CBD oil, sometimes labeled “hemp extract” or “full-spectrum hemp oil,” is extracted from the flowers, leaves, and stalks of the hemp plant and contains cannabidiol (CBD), the compound with potential anticonvulsant properties.
If you’re shopping for a product to help your dog’s seizures, look for one that lists CBD content in milligrams on the label. A product that says only “hemp oil” without specifying CBD concentration is likely hemp seed oil and won’t do anything for epilepsy.
What the Clinical Trials Show
The most widely cited study comes from Colorado State University, where neurologist Stephanie McGrath tested CBD in 16 pet dogs with epilepsy between 2016 and 2017. Nine dogs received CBD and seven received a placebo. Among the CBD group, 89 percent had a reduction in seizure frequency. Over a 12-week treatment period, dogs given CBD experienced roughly 33 percent fewer seizures than dogs on the placebo.
That sounds promising, but a larger and more recent study paints a more complicated picture. A double-blinded crossover trial of 51 dogs with drug-resistant epilepsy, published in the Journal of Veterinary Internal Medicine, found no statistically significant difference between CBD and placebo in reducing seizure days or total seizures. These were dogs already on standard anti-seizure medications that weren’t fully controlling their epilepsy, so the bar was higher. Still, the lack of a clear effect in a larger trial is worth noting.
The takeaway: CBD may help some dogs, particularly those with milder or more responsive forms of epilepsy. It is not a guaranteed fix, and it does not appear to be a reliable solution for dogs whose seizures already resist standard medications.
Full-Spectrum Extract vs. Pure CBD
Not all CBD products are created equal, and this matters for seizure management. Research published in Frontiers in Veterinary Science found that whole-plant hemp extracts containing a mix of cannabinoids (not just CBD) may work better than purified CBD alone. The idea is called the “entourage effect,” where minor cannabinoids, terpenes, and other plant compounds work together to boost the overall anticonvulsant activity.
The practical difference is striking. A meta-analysis of observational studies found that dogs given CBD-rich whole hemp extracts and dogs given purified CBD isolate both achieved similar response rates of about 35 to 40 percent (meaning a 50 percent or greater reduction in seizure frequency). But the dogs on whole hemp extract needed an average dose of just 6 mg per kilogram of body weight per day, while dogs on purified CBD isolate needed about 25 mg per kilogram to get the same result. That’s roughly four times less product with the full-spectrum version, which also means lower cost and potentially fewer side effects.
Side Effects to Watch For
CBD is generally well tolerated in dogs, but it’s not side-effect-free. The two most common effects owners report are increased appetite and sedation. Your dog may seem sleepier than usual, especially when first starting CBD or after a dose increase.
The more concerning issue involves the liver. Research from Cornell University’s College of Veterinary Medicine has shown that CBD can affect liver enzymes, specifically alkaline phosphatase and a family of enzymes involved in metabolizing medications. Elevated liver enzymes don’t always mean liver damage, but they do signal that the liver is working harder. If your dog is on CBD long-term, periodic bloodwork to monitor liver function is a reasonable precaution.
Interactions With Seizure Medications
Most dogs with epilepsy are already on prescription anti-seizure drugs, so the question of drug interactions is critical. The 51-dog trial specifically looked at whether CBD changed blood levels of four common seizure medications: phenobarbital, potassium bromide, zonisamide, and levetiracetam. Overall, no statistically significant interactions were found.
There was one flag, though. Dogs receiving CBD showed an average 11 percent increase in phenobarbital blood levels, compared to essentially no change during the placebo phase. That difference wasn’t large enough to reach statistical significance in this study, and it could reflect normal fluctuation. But phenobarbital is a drug where blood levels matter: too high and it causes excessive sedation and liver stress. Separately, earlier research found that CBD blood levels themselves increased when dogs were also taking phenobarbital, suggesting the two compounds may affect each other’s metabolism. The interaction between CBD and phenobarbital specifically has not been fully studied with long-term use, so extra monitoring makes sense if your dog takes both.
What to Expect Practically
Clinical trials have typically run for 12 weeks, so don’t expect overnight results. If CBD is going to help your dog, you’ll likely need at least a few weeks of consistent daily dosing before any change in seizure frequency becomes apparent. Even then, the realistic expectation is a reduction in seizures, not elimination. The Colorado State study showed a 33 percent decrease, which for a dog seizing multiple times per month could be meaningful.
CBD should not replace your dog’s existing seizure medications. Every clinical trial has studied it as an add-on treatment, not a replacement. Stopping prescribed anti-seizure drugs abruptly can trigger life-threatening clusters of seizures.
The Regulatory Reality
The FDA has not approved any cannabis-derived product for use in animals. No CBD product on the market has been evaluated by the FDA for safety, effectiveness, or quality in pets. There are no approved food additive petitions or official ingredient definitions for hemp-derived substances in animal food. In fact, adding THC or CBD to animal food products and selling them across state lines is technically a prohibited act under federal law.
What this means in practice: the CBD market for pets is unregulated. Product quality varies enormously. Some products contain less CBD than the label claims, others contain more THC than is safe for dogs. If you decide to try CBD, look for products that provide a certificate of analysis from an independent lab confirming the cannabinoid content and verifying that THC levels are extremely low (typically below 0.3 percent). Products specifically formulated for dogs, sold through veterinary channels or reputable pet companies, tend to be more reliable than generic hemp extracts marketed to humans.