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CBD is not a seizure rescue. If your dog is seizing for more than 5 minutes, or has two or more seizures in 24 hours, go to an emergency vet. Never stop or reduce your dog's anti-seizure medication to try CBD — abrupt withdrawal can trigger severe seizures. Every trial described below added CBD on top of dogs' existing medication.
The short answer: Three placebo-controlled trials have tested CBD added to seizure medication in dogs with drug-resistant epilepsy. All three found fewer seizures on average with CBD — a 33% median reduction at 2.5 mg/kg twice daily (Colorado State, 2019), a fall from 8.0 to 5.0 seizures with a CBD/CBDA hemp extract at 2 mg/kg twice daily (2022), and a 24% drop in seizure days at 9 mg/kg/day versus a 6% rise on placebo (51 dogs, 2023). But in two of the three, the number of dogs that improved by half or more was no different from placebo, a 5 mg/kg/day arm was stopped for futility, and liver enzymes rose in every trial. A 2025 systematic review judged the trials at moderate-to-high risk of bias and said no firm conclusion is possible yet. So: promising, unproven, and a conversation for your vet with bloodwork.
By Marc Brannigan and Natalie Mondine, co-founders of HempMy Pet · Published November 6, 2026 · Last reviewed November 6, 2026. We have grown and bottled full-spectrum hemp for pets on our own Colorado farm since 2016. We are not veterinarians — everything below comes from the published veterinary studies, consensus guidelines and drug labels listed at the end.
We sell hemp oil, so it is fair to ask why we would write a page this cautious. The answer is that owners of epileptic dogs are some of the most vulnerable customers in pet wellness, and this topic is full of exaggeration. Below is every controlled trial, what it found, what it did not find, and the questions worth taking to your vet. Our own product has not been studied for seizures, and we make no claim that it treats them.
The Three Placebo-Controlled Trials
| Trial | Dogs | CBD dose | Main result | Dogs with ≥50% fewer seizures | Side effects |
|---|---|---|---|---|---|
| McGrath et al., Colorado State, JAVMA 2019 | 26 enrolled, 16 analysed (9 CBD, 7 placebo), 12 weeks, parallel groups | 2.5 mg/kg twice daily, CBD-infused oil | Median 33% reduction in seizure frequency vs placebo | Similar in both groups | 2 dogs withdrawn for wobbliness; ALP rose significantly; no behavioural side effects reported |
| Garcia et al., Front Vet Sci 2022 | 14 dogs, 24-week crossover (12 weeks each arm) | 2 mg/kg twice daily, CBD/CBDA-rich hemp extract | Mean 8.0 seizures on placebo vs 5.0 on extract (P = .02); seizure days 5.8 vs 4.1 | 6 of 14 on extract vs 0 of 14 on placebo | Mild ALP rise; sleepiness 3/14, transient wobbliness 4/14 — not different from placebo |
| Rozental et al., Colorado State, JVIM 2023 | 51 dogs, double-blind crossover, 3 months each arm | 5 mg/kg/day (stopped after 12 dogs for futility), then 9 mg/kg/day in 39 dogs | At 9 mg/kg/day: seizure days −24.1% on CBD vs +5.8% on placebo; total seizures significantly lower | No significant difference | Liver enzymes rose at both doses; reduced appetite and vomiting more common on CBD |
Full citations below. All dogs stayed on their existing anti-seizure drugs.
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What Those Numbers Do and Don't Mean
The encouraging part: three independent placebo-controlled studies, from two research groups, using different products, all moved in the same direction. In the first Colorado State trial, dogs' blood CBD levels correlated with how much their seizures fell — the higher the level, the bigger the reduction — which is the kind of dose-response signal researchers look for. In the 2022 crossover, nearly half the dogs on the extract (6 of 14) cut their seizures by half or more, versus none on placebo.
The sobering part:
- "Responder" rates mostly didn't separate from placebo. In epilepsy research, the proportion of patients whose seizures fall by at least half is the standard benchmark. Two of the three trials failed it.
- Lower doses may not work. In the 51-dog trial, the 5 mg/kg/day dose — twice the per-dose amount in the first trial — met futility criteria after 12 dogs and was abandoned.
- The trials are small. 16, 14 and 39 dogs at the effective dose. A 2025 systematic review of these three randomised trials rated them at moderate-to-high risk of bias and concluded that "it is not possible to draw conclusions" on efficacy or the optimal dose. A 2022 review by European veterinary neurologists said much the same: clear-cut recommendations aren't possible yet.
- Funding. Colorado State's own announcement of the 2019 trial disclosed it was funded by the company that made the CBD oil, in which the lead investigator held a small stake. That does not invalidate the result, but it is the kind of detail you deserve to know.
An uncontrolled 2025 pilot in 13 dogs on two to six seizure drugs reported a significant drop in seizures (median 11 to 5) and in clusters, with 61.5% of dogs reaching a 50% reduction — but with no placebo group, that study can only suggest, not show.
The Liver-Enzyme Catch
Every trial found the same thing: CBD raises alkaline phosphatase (ALP), and sometimes ALT.
Context matters here. In a separate six-month placebo-controlled study at 4 mg/kg, ALP rose transiently in just over half the dogs on CBD, with no rise in other liver values, and the increase tracked bone-derived ALP — suggesting it was at least partly not from the liver. The AKC Canine Health Foundation, which funded the larger Colorado State trial, flagged ALT increases as a possible sign of liver stress when CBD is combined with other medications. And the human prescription CBD drug carries a similar warning: in Epidiolex's controlled trials, ALT rose above three times normal in 13% of patients versus 1% on placebo, mostly in people also taking valproate.
For a dog on phenobarbital — which also raises ALP — that means two drugs pushing the same blood test up. It does not make CBD off-limits, but it makes baseline bloodwork and rechecks non-negotiable. In the 2022 crossover, bloodwork was repeated at 2, 6 and 12 weeks.
Does CBD Interact With Phenobarbital, Bromide or Keppra?
Most interaction warnings online extrapolate from human liver enzymes. The canine data are more reassuring than those warnings suggest:
- Phenobarbital: in healthy Beagles given both, there was no significant change in the pharmacokinetics of either drug, and the authors advised against adjusting doses on that basis (Doran 2021).
- Phenobarbital, bromide, zonisamide: serum levels did not change when the CBD/CBDA extract was added (Garcia 2022). The 51-dog trial likewise found no change in anti-seizure drug levels.
- Liver enzymes in dogs: laboratory work found CBD is cleared mainly by canine CYP1A2 and CYP2C21, inhibits CYP2B11 and CYP2D15, but does not inhibit CYP3A12 — the dog enzyme most human-based warnings assume.
See our phenobarbital guide, Keppra guide and the full hemp and dog medications guide.
How Much CBD Was Used in the Seizure Trials?
We will report what the studies used; the decision about your dog belongs with your vet.
- 2 mg/kg twice daily (CBD/CBDA-rich extract; 4 mg/kg/day) — Garcia 2022.
- 2.5 mg/kg twice daily (5 mg/kg/day) — McGrath 2019.
- 5 mg/kg/day — stopped for futility; 9 mg/kg/day — significant effect on seizure days — Rozental 2023.
- For comparison, the human drug Epidiolex starts at 2.5 mg/kg twice daily and goes up to 10 mg/kg twice daily.
Two things owners rarely hear. First, these doses are far higher than the everyday wellness servings on most pet hemp labels, including ours — which matters for both cost and liver monitoring. Second, how CBD is given matters: dogs absorb it poorly by mouth, and the 2022 neurologists' review notes that oil-based formulations and giving it with food improve absorption. Holding oil in the cheek pouch did not increase absorption compared with swallowing in one study.
Do Vets Recommend CBD for Dogs With Seizures?
Some do, as an add-on in drug-resistant dogs, and many will discuss it — but the published neurology consensus is cautious, and no veterinary body has endorsed a CBD dose for epilepsy. The AKC Canine Health Foundation's advice to owners is sensible: talk to your vet before starting, watch for appetite or behaviour changes, and ask about liver testing if your dog takes multiple medications. A follow-up study it funded is refining dosing and formulation. Bring this page and its citations to the conversation.
What Is the Best CBD Oil for Dog Seizures?
No CBD product has been proven better than another for seizures, and no product — ours included — is approved to treat epilepsy in dogs. If you and your vet decide to try one, the trials and reviews point to what to check:
- A certificate of analysis (COA) for every batch showing the real CBD content per mL, the THC level (under 0.3% for hemp), and screening for pesticides, solvents and heavy metals. The 2022 review stresses that product quality varies widely.
- A known concentration so your vet can calculate mg/kg precisely.
- An oil base, given with food, for better absorption.
- No xylitol or other ingredients toxic to dogs.
- Not a marijuana product. THC can cause wobbliness, tremors and dribbling urine in dogs, and marijuana edibles are a common poisoning.
Full-spectrum extract in cold-pressed hemp seed oil, grown and bottled on our own Colorado farm, third-party tested every batch with published COAs. It is the oil used in our 90-day joint study — it has not been studied for seizures, and we do not claim it treats them. If you are considering CBD alongside seizure medication, start with your vet and bloodwork. $99
Shop 1,000mg Hemp Seed Oil → See the StudyIf You and Your Vet Decide to Try It
- Keep every seizure medication exactly as prescribed. CBD was always an add-on in the trials.
- Get baseline bloodwork — liver values, and your dog's anti-seizure drug levels.
- Keep a seizure diary for at least a month beforehand, so you have a real baseline to compare against.
- Change one thing at a time. Don't start CBD the same month as a dose change.
- Recheck bloodwork — the 2022 trial checked at 2, 6 and 12 weeks.
- Watch for wobbliness, sleepiness, vomiting and appetite loss, which were the most common side effects.
- Give it at least 12 weeks before judging — the trial length — unless side effects appear.
Questions to Ask Your Vet
- Is my dog drug-resistant, and have we optimised the standard drugs first?
- Given the trial results, is CBD a reasonable add-on for my dog?
- What dose would you want to use, and how will we monitor liver values alongside phenobarbital?
- What would count as success, and when do we decide it isn't working?
- Is the product I'm considering acceptable to you, based on its COA?
Frequently Asked Questions
Does CBD actually help dogs with seizures?
Possibly, as an add-on to seizure medication. Three placebo-controlled trials in dogs with drug-resistant epilepsy found fewer seizures on average with CBD than placebo: a 33% median reduction, a drop from 8.0 to 5.0 seizures, and a 24% reduction in seizure days. But in two of the three, the share of dogs whose seizures fell by half or more was no different from placebo, and a 2025 systematic review said firm conclusions are not yet possible. CBD has not been shown to replace seizure medication.
How much CBD should I give my dog for seizures?
That is a decision for your veterinarian. For reference, the controlled trials used 2 mg/kg twice daily of a CBD/CBDA extract, 2.5 mg/kg twice daily of CBD, and 9 mg/kg per day of CBD; a 5 mg/kg per day dose was stopped for futility. These amounts are much higher than typical wellness servings on pet hemp labels, and liver enzymes rose in every trial, so bloodwork before and during use is important.
Do vets recommend CBD for dogs with seizures?
Some vets will discuss or recommend CBD as an add-on for dogs whose seizures are not controlled by standard medication, but veterinary neurology reviews say the evidence is not yet strong enough for clear recommendations, and no veterinary body has endorsed a dose. The AKC Canine Health Foundation advises talking to your vet first and asking about liver testing.
What is the best CBD oil for dog seizures?
No product has been shown to be better than another for seizures, and none is approved to treat canine epilepsy. If your vet agrees to a trial, choose a product with a batch-specific certificate of analysis showing CBD content, THC under 0.3% and contaminant testing, a known concentration, an oil base, and no xylitol. Avoid marijuana products.
Can CBD replace phenobarbital in dogs?
No. Every controlled trial gave CBD in addition to the dogs' existing anti-seizure drugs. There is no evidence that CBD can replace phenobarbital, and stopping phenobarbital suddenly can cause severe seizures or status epilepticus.
Is CBD safe for dogs on seizure medication?
In the trials, CBD did not change blood levels of phenobarbital, bromide or zonisamide, and side effects were mostly mild: wobbliness, sleepiness, vomiting and reduced appetite. However, CBD raised the liver enzyme ALP in every trial, sometimes substantially, and phenobarbital raises it too. Baseline and follow-up bloodwork with your vet is essential.
How long does CBD take to work for seizures in dogs?
The controlled trials ran each treatment phase for about 12 weeks before measuring results. A fair trial in an individual dog, with your vet, usually means at least that long with a seizure diary kept before and during use.
Can CBD stop a seizure in progress?
No. CBD is not a rescue medication and should never be given to a dog that is seizing. Rescue medications such as intranasal midazolam or rectal levetiracetam must be prescribed by your vet. A seizure lasting more than 5 minutes is an emergency.
The Short Version
CBD added to seizure medication lowered seizure frequency on average in three small placebo-controlled dog trials, but the proportion of dogs that improved by half or more mostly matched placebo, lower doses may not work, and liver enzymes rose every time. It does not appear to change phenobarbital or bromide levels, but it complicates liver monitoring. It is not a rescue and not a replacement for medication. If you want to try it, do it with your vet, a seizure diary, a quality-tested oil and bloodwork.
Third-party tested full-spectrum hemp — not studied for seizures, not a replacement for anti-seizure medication
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Dog Seizures · Epilepsy in Dogs · Phenobarbital for Dogs · Keppra for Dogs · Seizures & End-of-Life Decisions · Cat Seizures · Hemp & Dog Medications
Marc co-founded HempMy Pet in 2016 with his business partner Natalie Mondine, the company's COO. HempMy Pet breeds its own hemp genetics, grows them on its own Colorado farm, and formulates every batch in-house under human-grade standards — seed to sale, nothing sourced overseas. Every batch is third-party tested and the certificates of analysis are published. More about us.
HempMy Pet ran its own 90-day study of 37 dogs with chronic joint discomfort. Of the 32 that completed it, 30 (93%) showed a benefit, and 94% of owners reported their dog's quality of life had improved. It was overseen by Dr. Robin Downing, DVM, MS of the Downing Center for Animal Pain Management, with Lori Kogan, Ph.D. and Peter W. Hellyer, DVM of Colorado State University's College of Veterinary Medicine & Biomedical Sciences, and published in the Journal of the American Holistic Veterinary Medical Association. Read the methodology.
Why Dr. Downing: in 2005 she became only the third veterinarian in the world credentialed as a Diplomate of the American Academy of Pain Management. She founded the International Veterinary Academy of Pain Management, is a Diplomate of the ACVSMR, a Certified Veterinary Pain Practitioner and a Certified Canine Rehabilitation Practitioner, and was the AVMA's 2020 Bustad Companion Animal Veterinarian of the Year. Read the published paper (PDF).
This article is general information for dog owners, not veterinary advice. It is reviewed and updated as new peer-reviewed evidence is published, and where the evidence is thin or negative we say so.
How We Sourced This Article
Every claim above traces to one of these.
- 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. J Am Vet Med Assoc. 2019;254:1301–1308. PubMed. Funding disclosed by CSU: the trial was funded by the maker of the CBD oil.
- Garcia GA, Kube S, Carrera-Justiz S, Tittle D, Wakshlag JJ. Safety and efficacy of cannabidiol-cannabidiolic acid rich hemp extract in the treatment of refractory epileptic seizures in dogs. Front Vet Sci. 2022;9:939966. PubMed.
- Rozental AJ, Weisbeck BG, Corsato Alvarenga I, et al. The efficacy and safety of cannabidiol as adjunct treatment for drug-resistant idiopathic epilepsy in 51 dogs: a double-blinded crossover study. J Vet Intern Med. 2023;37:2291–2300. PubMed.
- Jensen TM, Olsen PJ, Arendt ML, et al. Cannabidiol treatment for refractory idiopathic epilepsy in dogs: a systematic review with risk of bias assessment. Prev Vet Med. 2025. PubMed. Also Potschka H, et al. Cannabidiol in canine epilepsy. Vet J 2022, PubMed.
- Kimram A, Suwanna N, Tiraphut B, et al. An exploratory study of cannabidiol as an adjunctive treatment for refractory epilepsy in dogs. Animals. 2025. PubMed. Single-arm, no placebo.
- Doran CE, McGrath S, Bartner LR, et al. Drug-drug interaction between cannabidiol and phenobarbital in healthy dogs. Am J Vet Res. 2021;83:86–94. PubMed.
- Court MH, Mealey KL, Burke NS, et al. Cannabidiol and cannabidiolic acid: preliminary in vitro evaluation of metabolism and drug-drug interactions involving canine cytochrome P-450, UDP-glucuronosyltransferase, and P-glycoprotein. J Vet Pharmacol Ther. 2024;47:1–13. PubMed.
- Bradley S, Young S, Bakke AM, et al. Long-term daily feeding of cannabidiol is well-tolerated by healthy dogs. Front Vet Sci. 2022;9:977457. PubMed.
- Della Rocca G, Paoletti F, Conti MB, et al. Pharmacokinetics of cannabidiol following single oral and oral transmucosal administration in dogs. Front Vet Sci. 2022. PubMed.
- US Food and Drug Administration. EPIDIOLEX (cannabidiol) oral solution, prescribing information: indications, hepatocellular injury warning, dosing.
- Colorado State University and AKC Canine Health Foundation. CSU: Results from CBD clinical trial (2019, with funding disclosure) · AKC CHF: Evidence for the use of CBD in canine idiopathic epilepsy.
- Kogan L, Hellyer P, Downing R. The Use of Cannabidiol-Rich Hemp Oil Extract to Treat Canine Osteoarthritis-Related Pain: A Pilot Study. J Am Holist Vet Med Assoc. 2020;58:35–45. Our disclosure: HempMy Pet supplied the hemp extract and reimbursed clinic costs; we had no involvement in any other study cited here.
Spot something that conflicts with your veterinarian's advice? Email support@hempmypet.com and we will correct it.
These statements have not been evaluated by the Food and Drug Administration. Our products are not intended to diagnose, treat, cure, or prevent any disease. This article is general information, not veterinary advice. CBD is not a substitute for anti-seizure medication — never start, stop or change your dog's medication without your veterinarian.
