Pet Education

Marijuana Toxicity: Don’t be afraid to tell your veterinarian if your dog may have been exposed.

Marijuana Toxicity in Dogs

Marijuana toxicity in dogs can occur through inhalation of secondhand smoke, or more commonly through ingestion of the leaves, seeds, stems and flowers of the plant, or ingestion of products made with concentrated THC butter or hash oil.

By Nicole DeNezzo, DVM
Emergency + Critical Care

Marijuana is a drug that has long been used recreationally by humans for it’s psychoactive properties, but has also become more popular for it’s medicinal use. Marijuana comes from the dried leaves and flowers of the plant, Cannabis sativa. The plant produces over 60 chemical compounds known as cannabinoids, the major one being tetrahydrocannabinol (THC). The THC concentration of marijuana can vary greatly depending on cultivation techniques and formulations.

The incidence of marijuana toxicity in dogs has increased in states that have legalized marijuana for medical use or have passed laws decriminalizing possession of small amounts for personal use.[1]

Clinical Signs

Dogs can start to show symptoms of marijuana toxicity about an hour after ingestion. The most common signs include disorientation, depression, a drunken gait, dribbling urine, dilated pupils, hypersensitivity to motion or sound, and tremors. Even though marijuana possesses anti-nausea properties, dogs may exhibit vomiting due to gastrointestinal upset secondary to ingestion of the plant material.

Other signs include an abnormally slow or fast heart rate, respiratory rate, or temperature. In severe cases dogs may be comatose. The severity of clinical signs varies greatly depending upon the concentration and dose of THC ingested. Ingestion of products made with medical grade THC butter results in more severe clinical signs due to the high THC concentration. Clinical signs can persist for 1-3 days.[2]


The diagnosis of marijuana toxicity is based largely on known exposure to the drug so it is very important to share this information with your veterinarian. There is no drug test designed specifically for use in dogs. Urinary drug tests designed for humans can sometimes confirm a suspicion for marijuana toxicity if the result is positive, but there is a high incidence of false negative test results. The human drug test may be inaccurate in dogs if the urine is tested too soon after exposure to the drug. The test may also be inaccurate because dogs metabolize THC into a different compound that is excreted into the urine, which is not detected.[1]

Similar clinical signs to marijuana toxicity can be seen with other drug toxicities or diseases affecting the central nervous system. Therefore it is important to tell your veterinarian about a possible marijuana ingestion to help rule out other, more serious conditions.

Dog with Bag of CannabisTreatment

If the ingestion of marijuana was recent and there is no sign of depression or agitation, emesis (vomiting) can be induced. An activated charcoal solution can also be administered to bind to and prevent reabsorption of the drug from the intestinal tract. If the dog is already showing signs of depression or appears to be severely affected, these steps of decontamination maybe contraindicated because there is increased risk of developing aspiration pneumonia.[2]

Treatment largely involves supportive care. Dogs should be kept in a quiet, dark place. Administration of intravenous fluids can help prevent dehydration in dogs that have been vomiting or are too sedate to eat and drink. In severe cases, an intravenous lipid (fat emulsion) infusion can be used to treat THC toxicity because it is highly fat-soluble.


The prognosis of dogs treated for marijuana toxicity is generally good, but varies with the dose and concentration of THC ingested. The more concentrated forms of THC, such as that found in THC butter, can have more severe clinical signs and have resulted in 2 reported fatalities.[1]

Avoid a trip to the ER

Marijuana toxicity can be easily avoided if all products containing THC are stored in a safe place where your dog cannot access them. If an accidental ingestion does occur, don’t be afraid to share this information with your veterinarian. We just want to be able to help your pet and make the appropriate treatment recommendations.

REFERENCES: [1] Meola, Stacy, et al. Evaluation of trends in marijuana toxicosis in dogs living in a state with legalized medical marijuana: 125 dogs (2005-2010). J Vet Emer Crit Care 2012; 22(6): 690-696. [2] Fitzgerald, Kevin, et al. Marijuana Poisoning. Top Companion Anim Med 2013; 28: 8-12.

Animal Specialty Group

DVM, Emergency + Critical Care

Dr. Nicole DeNezzo has special interests in endocrine disease, neurology, and shelter medicine. She received her DVM from Tufts University and is new newest member of ASG’s Emergency + Critical Care team.