Marijuana Toxicity in Dogs

TL;DR. Marijuana toxicity in dogs is a common poisoning caused by the ingestion of THC, leading to neurological symptoms like extreme sleepiness, sensitivity to sound and touch, and urinary incontinence.

Dogs with marijuana toxicity often present with profound lethargy and depression.

What is it?

Marijuana toxicity, also known as THC toxicity or cannabinoid toxicity, is a poisoning that occurs when a dog is exposed to tetrahydrocannabinol (THC), the primary psychoactive compound found in the cannabis plant. While cannabis products have become increasingly common in households, they pose a significant danger to our canine companions. Dogs are far more sensitive to the effects of THC than humans are, meaning even a small amount can cause severe clinical signs.

The reason for this heightened sensitivity lies in the canine brain. Dogs possess a significantly higher number of cannabinoid receptors—specifically CB1 receptors—in their brain tissue compared to humans. When THC enters a dog's system, it binds to these receptors, disrupting normal neurotransmitter pathways. This disruption leads to a combination of central nervous system depression and sensory hypersensitivity, causing the dog's nervous system to become simultaneously sluggish and easily startled.

As noted in international veterinary guidelines, the specific clinical effects of cannabis can vary widely depending on the unique proportions of active cannabinoids, terpenes, and flavonoids present in the specific plant strain or product. Understanding this condition is crucial for pet owners, as accidental exposures have risen dramatically. Whether a dog ingests dried cannabis flower, eats a THC-infused edible, or inhales secondhand smoke, the resulting toxicosis requires prompt recognition and veterinary attention to prevent complications and ensure a smooth recovery.

Causes & risk factors

The primary cause of marijuana toxicity in dogs is the ingestion of products containing THC. Dogs are natural scavengers and are often attracted to the smell or taste of cannabis products, particularly when they are baked into edible goods. Common sources of exposure include:

• Edibles: Brownies, cookies, gummies, and chocolates infused with THC. Edibles are especially dangerous because they often contain additional canine toxins, such as chocolate or xylitol (an artificial sweetener), which can be life-threatening on their own.
• Dried plant material: Ingesting loose marijuana buds, leaves, or joint remnants (roaches) left in accessible areas or discarded outdoors.
• Concentrates and oils: THC distillates, vape cartridges, and medical-grade cannabis oils. These products contain highly concentrated levels of THC, which can cause rapid and severe poisoning in small doses.
• Secondhand smoke: Inhaling smoke in enclosed spaces where cannabis is being used.

There are no documented breed predispositions for marijuana toxicity; any dog, regardless of breed, age, or size, can be affected. However, small-breed dogs face a higher risk of severe toxicity due to their low body weight. A dose of THC that might cause mild drowsiness in a large dog can lead to severe sedation or coma in a smaller dog. Additionally, puppies are at a higher risk due to their curious nature and developing organ systems.

Signs to watch for

The clinical signs of marijuana toxicity typically appear within 30 to 90 minutes after ingestion, or even sooner if the toxin was inhaled. Because THC is fat-soluble, it is stored in the body's fat tissues, meaning the symptoms can persist for up to 72 hours.

Key symptoms to watch for include:

• Central nervous system depression (Common): Your dog may appear extremely lethargic, sleepy, or "spaced out." They may struggle to keep their head up or stand, often swaying from side to side (ataxia).
• Sensory hypersensitivity (Common): Despite being drowsy, affected dogs are often hyper-reactive to their environment. A sudden sound, a change in light, or a gentle touch can cause them to flinch, startle violently, or lose their balance.
• Urinary incontinence (Common): Dribbling urine involuntarily is one of the most classic and telling signs of marijuana toxicity in dogs.
• Anxiety (Common): Some dogs experience dysphoria and agitation instead of sedation, leading to pacing, whining, and general distress.
• Tachycardia (Common): An abnormally rapid heart rate, which can contribute to the dog's overall anxiety and physiological stress.
• Death (Rare): While extremely rare, fatalities can occur if a dog ingests a massive dose of concentrated THC, or if the exposure is complicated by other factors, such as inhaling vomit into the lungs (aspiration pneumonia) or consuming co-toxins like chocolate.

Urinary incontinence is a classic clinical sign of THC toxicity in dogs.

If your dog exhibits severe sedation, is completely unresponsive, experiences seizures, or has a dangerously slow heart rate, this is a red-flag emergency that requires immediate veterinary intervention.

How vets diagnose it

Diagnosing marijuana toxicity relies heavily on a combination of clinical signs, physical examination findings, and a history of potential exposure. Because there is no single, widely available "gold standard" laboratory test that instantly confirms THC poisoning in dogs, your vet will look for the classic triad of symptoms: profound depression, sensory hypersensitivity (startling easily), and urinary incontinence.

During the physical exam, your vet will assess your dog's vital signs, checking for tachycardia (fast heart rate) or bradycardia (slow heart rate), abnormal body temperature, and neurological reflexes. They will also perform basic diagnostic tests, such as a complete blood count and chemistry panel, to rule out other potential toxins or underlying health issues that could mimic these symptoms.

Over-the-counter human urine drug screening tests are sometimes used in veterinary clinics, but they are not entirely reliable for dogs. Dogs metabolize THC into different chemical compounds than humans do, which frequently leads to false-negative results on human drug tests.

For this reason, providing an honest history is the most valuable diagnostic tool. Veterinarians are bound by confidentiality and are not required to report pet owners to law enforcement for cannabis exposure. Being upfront about what your dog may have ingested allows the veterinary team to bypass unnecessary, expensive diagnostic tests and begin targeted supportive care immediately.

Treatment options

There is no specific antidote for THC toxicity. Instead, veterinary treatment focuses on supportive care, managing neurological symptoms, and helping the dog's body safely eliminate the toxin.

The approach to treatment depends largely on how recently the exposure occurred and how severely the dog is affected.

Decontamination

If the ingestion occurred within 1 to 2 hours and the dog is not yet showing neurological signs, your vet may attempt to induce vomiting to remove the remaining material from the stomach. However, if your dog is already drowsy, uncoordinated, or unresponsive, inducing vomiting is strictly avoided. This is because THC suppresses the gag reflex, putting the sedated dog at a high risk of inhaling vomit into their lungs, which can cause life-threatening aspiration pneumonia.

Your vet may also administer activated charcoal by mouth or through a stomach tube. Activated charcoal binds to the toxins in the gastrointestinal tract, preventing them from being absorbed into the bloodstream. Because THC undergoes enterohepatic recirculation (meaning it is reabsorbed by the intestines after being processed by the liver), multiple doses of activated charcoal may be given over a 24-hour period.

Supportive Care and Monitoring

For dogs showing active symptoms, hospitalization is often required to provide a safe, controlled environment. Supportive therapies include:

• Intravenous (IV) fluid therapy: Helps maintain hydration, supports blood pressure, and assists the kidneys in processing metabolic waste.
• Temperature regulation: Dogs under the influence of THC can experience hypothermia (low body temperature) or hyperthermia (high body temperature). Vets will use warming blankets or cooling fans as needed to keep your dog's temperature stable.
• Sensory reduction: Because affected dogs are hypersensitive to light and sound, they are typically housed in a quiet, darkened ward with padded bedding to prevent self-injury during startle responses.

Neurologic Support

When managing the neurological impacts of the toxin, vets must carefully tailor their support to the dog's specific clinical state. As noted in a leading veterinary critical care reference:

"Central nervous system (CNS) stimulatory (e. g. , agitation, tremors, seizures) or sedatory (e. g. , drowsiness, severe sedation, coma) clinical signs ar" — Small Animal Critical Care Medicine, p.433

If a dog is highly agitated or experiencing tremors, your vet may administer mild sedatives or anti-seizure medications to calm the nervous system. Conversely, if the dog is in a state of severe sedation or coma, they will receive intensive monitoring, frequent turning to prevent pressure sores, and respiratory support if their breathing becomes shallow.

Hospitalization with intravenous fluid therapy and a quiet environment helps dogs recover safely.

Advanced Therapies

In severe cases where a dog has ingested a massive dose of THC and remains comatose or highly unstable, your vet may recommend Intravenous Lipid Emulsion (ILE) therapy. This treatment involves administering a sterile fat solution directly into the bloodstream. Because THC is highly fat-soluble, it binds to the lipid molecules in the blood, preventing the toxin from reaching the brain tissues and accelerating its elimination from the body.

Prognosis

Long-term prognosis data in this species is limited within our primary structured records; however, standard veterinary clinical experience indicates that the prognosis for marijuana toxicity in dogs is generally excellent.

With prompt supportive care, the vast majority of dogs make a full recovery within 24 to 72 hours without any lasting side effects. The duration of recovery depends on the amount of THC ingested, the size of the dog, and how quickly treatment was initiated. The primary factors that can worsen the prognosis are secondary complications, such as severe aspiration pneumonia or the concurrent ingestion of other highly toxic substances like chocolate or xylitol.

Prevention

Marijuana toxicity is entirely preventable. By taking proactive steps, you can protect your dog from accidental exposure:

• Secure storage: Store all cannabis products, including dried flower, edibles, oils, and medical treatments, in child-proof, pet-proof containers. Keep these containers in high cabinets or locked drawers that your dog cannot access.
• Safe disposal: Dispose of joint remnants, vape cartridges, and packaging in secure, outdoor trash cans. Dogs are notorious for raiding indoor wastebaskets.
• Vigilance on walks: Keep your dog on a leash during walks, especially in public parks, urban areas, or hiking trails where people may have discarded cannabis products. Prevent your dog from eating unknown substances off the ground.
• Guest education: Inform visitors to your home that you have a curious pet. Ask them to keep their bags, coats, and personal items closed and placed out of your dog's reach.

When to call your vet

If you suspect or know that your dog has ingested marijuana or been exposed to THC, call your veterinarian or a pet poison control hotline immediately. Do not wait for symptoms to appear, as early intervention can make treatment much simpler and less expensive.

Seek emergency veterinary care immediately if your dog exhibits any of the following red flags:

• Complete unresponsiveness or difficulty waking up
• Difficulty breathing or very slow, shallow breaths
• Seizures or severe muscle tremors
• Inability to stand or walk
• Ingestion of a cannabis edible that also contains chocolate, raisins, or xylitol

Sources

• Small Animal Critical Care Medicine, p. 433
• wsava-pain-vpat-thai, p. 93