Can Dogs Have Bad Reactions to CBD?

Yes, it is possible for dogs to have side effects to CBD like for example, vomiting, diarrhea, and lethargy. The risk of unwanted side effects is greater if using high CBD doses. On the other hand, if sticking to the veterinarian’s instructions, high-quality CBD oil made for dogs is safe. 

According to the World Health Organization, “CBD is generally well-tolerated, with a good safety profile.” Recent studies agree with this statement. In a 2018 study from the Colorado State University called “A Report of Adverse Effects Associated With the Administration of Cannabidiol in Healthy Dogs,” it is said that “CBD is a well-tolerated supplement.” Later on, the same findings were concluded in a 2019 study, “Single-Dose Pharmacokinetics and Preliminary Safety Assessment with Use of CBD-Rich Hemp Nutraceutical in Healthy Dogs and Cats.”

Can Dogs Have Bad Reactions to CBD

However, the bad news is that every dog is different, and some are more sensitive than others. Namely, not all dogs are expected to develop severe side effects, but there are those that might.  

To understand the possible side effects, dog owners need to be familiar with how CBD affects dogs along with what it is and how CBD works. CBD (cannabidiol) is a natural compound extracted from the cannabis plant. More importantly it’s made from the hemp plant and not marijuana plants. 

In veterinary medicine, the CBD pet wellness trend is relatively new, and there is not a lot of research and definitive scientific data about its medicinal use. Therefore, most conclusions about possible benefits and negative effects are drawn from human studies. 

So far, clinical trials from researchers and anecdotal evidence from pet parents support the claims that the potential benefits of CBD can be helpful for various conditions. CBD can help in dog arthritis, like joint pain, chronic pain, and neuropathic pain, allergies, cancer, and seizures (alone or combined with seizure medications). It also has anti-inflammatory properties and anti-nausea effects. Plus, CBD oil can help with insomnia and arthritis in senior dogs and has a positive impact on appetite stimulation.

What are the Side Effects of CBD Oil in Dogs?

What are the Side Effects of CBD Oil in Dogs

The top three side effects of CBD oil in dogs are dry mouth, lethargy, and drowsiness. Although there are some safety concerns, there are two important things to remember. First, CBD is a dietary supplement with a good safety profile, and second, the health benefits of CBD oil outweigh the risk of adverse reactions. 

Before we take a closer look into the different side effects of CBD oil in dogs, here is a short list of what to expect after you start your dog on CBD oil:

  • Dry mouth
  • Lowered blood pressure 
  • Lethargy
  • Dizziness
  • Diarrhea
  • Vomiting
  • Inhibited liver enzymes 
  • Dog upset stomach

Dry mouth

Dry mouth is one of the potential side effects of CBD oil in dogs. CBD reduces saliva production, which results in unusual dryness of the mouth. If persisting over a longer course, dry mouth can cause pain while swallowing, bad breath, and even teeth issues, even if proper dental hygiene is maintained. To combat such adverse effects, you need to ensure your dog has constant and easy access to fresh drinking water. 

Lowered Blood Pressure

CBD triggers a temporary drop in the dog’s blood pressure, especially if given in high doses. The blood pressure drop results in light-headedness and dizziness. The good news is that this side effect is dose-dependent, meaning you can easily solve it by using lower doses of CBD. 


Lethargy in dogs is a common side effect of CBD. If your dog is sluggish, sleepy, and lazy after its daily dose of CBD, it means you are giving it too much CBD oil. In such a case, you should decrease the dose and see if lethargy is avoided. In most cases, the dosage modification will prevent similar issues in the future.   


Another potential side effect of CBD oil in dogs is dizziness. Signs indicating your dog is feeling dizzy include trouble standing up, losing balance, and falling over. Dizziness is likely to occur if using a CBD product made for humans (which contains THC). While the psychoactive effects are pleasing for some people, for dogs, THC is toxic. In severe cases, THC ingestion can be lethal. To minimize the risk of such a scenario, you must use THC-free CBD products made for pets.   


Dog diarrhea is a common issue in dogs and can be caused by many different things. If the diarrhea is triggered by CBD oil use, you have two options, reduce the dosage or stop giving your dog CBD. Alternatively, you can also try using another CBD brand. This is because diarrhea can be triggered by the carrier oil and not the CBD itself. 


Vomiting is another potential side-effect of CBD use in dogs. The dog vomiting can be triggered by the CBD compound itself, the essential oils used as carriers, or the supplement’s overall bitter taste. If the taste is too upsetting for your dog, you should try a dog-friendly flavored CBD oil like chicken, bacon, or beef. 

Inhibited Liver Enzymes

CBD impacts the production of liver enzymes. Scientific data on the topic is conflicting as some research shows it causes increased levels of alkaline phosphatase while others demonstrate it inhibits the liver enzymes. If the liver enzymes are inhibited, the dog cannot properly metabolize drugs which put it at risk of accidental overdoses. To avoid such side effects of CBD usage, you need to consult with a vet whether your dog’s current medications are compatible with this holistic treatment. 

Upset Stomach

Basically, any new food or new medication can trigger a stomach upset in dogs. Sadly, CBD is not an exception. To minimize the risk of stomach upset, it is advisable to start with small amounts and gradually increase the dose of CBD as your dog’s body gets used to the new supplement. Giving your dog too much CBD all of a sudden will result in several potentially serious side effects, including stomach upset. 

CBD Dog Treats Side Effects

The side effects associated with CBD dog treats like soft chews, bites, and other edibles are the same as with CBD oil. Depending on the other compounds and ingredients used in the treats, they can also trigger allergic reactions (something oils are unlikely to do). 

The good news is that treats come with the same potential benefits of CBD as the oil versions. Plus, there is a better chance of dosing picky eaters with treats than it is with oils. 

Can CBD Treats Make Dogs Sick?

Yes, CBD treats can make dogs sick, causing vomiting, diarrhea, lack of appetite, or lethargy. Luckily, the side effects of CBD dog treats are transient and tend to resolve once the dog gets used to the new addition of CBD. 

Risks of Using CBD Oil for Dogs

According to Dr. Jerry Klein, Chief Veterinary officer at the American Kennel Club, “when it comes to CBD oil for dogs, there’s a lot of information floating around the internet.” This sums up why you need to talk with your trusted vet before using CBD products on your pets.  Namely, it is hard for pet owners to differentiate between accurate information and exaggerations. 

Also, do not forget that CBD hemp oil is not a prescription drug, and it is not approved for use in pets by the Food and Drug Administration (FDA). Therefore, state laws on a federal level prohibit vets from recommending CBD. In such a case, it is a good idea to find a licensed holistic veterinarian experienced in the use of hemp products for pets and capable of answering all of your CBD-related questions.  

So, first, you need to tell the vet about the medications and supplements your dog is using at the moment to check if they are compatible with CBD oil. Then you need to discuss dosage. You should always opt for the lowest possible dose that can achieve the desired effect. That way, your dog will enjoy the potential benefits without risking side effects. 

Last but not least, you must always use CBD oil made for pets. Human CBD products contain high levels of THC, which is toxic to dogs. THC toxicity manifests with decreased heart rate, respiratory depression, urinary incontinence, and neurological signs (loss of coordination, vocalization, tremors, seizures). Worst-case scenario, THC ingestion in dogs can have a fatal outcome. 

How Long do Side Effects of CBD Oil Last in Dogs?

How Long do Side Effects of CBD Oil Last in Dogs

Usually, the side effects of CBD oil persists for a couple of days. Generally speaking, you should call your veterinarian if the adverse reactions and negative effects are present after three to four days of using CBD. Most side effects are dose-dependent, and dogs are likely to experience a significant decrease in the frequency and intensity after a simple dosage modification.

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