What happens if a dog takes too much CBD?
Controlled studies have tested CBD in dogs at doses far above what most owners give and documented the effects. A 2020 randomized, placebo-controlled study tested escalating doses in 20 healthy Beagles, reaching a peak single dose of 64.7 mg/kg CBD. The dogs showed lethargy and increased sensitivity to touch, but all tolerated the dose without serious harm. A 2024 safety study gave 32 healthy Beagles 5 mg/kg CBD daily for 90 consecutive days and found the dose well tolerated with no major adverse events.
The 2018 Cornell study of CBD for osteoarthritis used 2 mg/kg twice daily. The doses tested in safety trials are multiples of what most dogs receive.
The side effects documented in these trials were mild and temporary: sedation, unsteady gait, vomiting, and diarrhea. No study has documented a fatal overdose from CBD alone.
What are the actual side effects of high-dose CBD?
Sedation is the most common effect. Dogs given high doses become very sleepy, difficult to rouse, or unresponsive for several hours. The 2020 escalating-dose study documented lethargy as an adverse event, and the effect resolved as the CBD cleared the system.
Loss of coordination, called ataxia, appears at higher doses. The dog may walk unsteadily, bump into objects, or seem disoriented. This effect looks similar to mild alcohol intoxication and typically lasts a few hours.
Gastrointestinal upset is also common. Vomiting and diarrhea occur more often when CBD is given on an empty stomach or when the dose is much higher than the dog is accustomed to. The carrier oils in most CBD products, such as coconut oil or MCT oil, can contribute to stomach upset in sensitive dogs.
These effects are uncomfortable but not dangerous on their own. They peak within one to two hours of ingestion and usually resolve within four to twelve hours, depending on the dose and the dog's size.
How much CBD did the studies test?
The 2020 escalating-dose trial tested single doses up to 64.7 mg/kg in healthy dogs. The dogs showed mild constitutional signs but no life-threatening events.
The 2024 NASC safety study tested 5 mg/kg daily for three months. The study found the dose well tolerated with no serious adverse events.
A 2023 epilepsy trial of 51 dogs used 9 mg/kg daily as an add-on to anti-seizure medications and documented significant liver enzyme elevations, discussed below.
Most owners give far less. Even if a dog accidentally ingests an entire bottle, the dose is rarely in the range these trials tested.
What about liver damage?
The 2023 epilepsy study found significant elevations in ALP and ALT liver enzymes in dogs receiving CBD daily alongside anti-seizure drugs. Both markers rose substantially over the three-month treatment period, according to the trial.
Whether this represents liver stress or benign enzyme induction is not yet clear. No study has documented clinical liver disease, jaundice, or liver failure from CBD alone, but the enzyme changes are real and warrant monitoring. Dogs on long-term CBD, especially at higher doses or in combination with other medications, should have bloodwork checked periodically. Talk to your vet about a monitoring schedule if your dog is on CBD for a chronic condition.
Is the danger from CBD or from THC?
Most emergency vet visits related to cannabis products involve THC, not CBD. THC is the psychoactive compound in cannabis and causes more severe toxicity in dogs. Signs of THC toxicity include dilated pupils, extreme sensitivity to sound and touch, dribbling urine, tremors, slow heart rate, and in severe cases, seizures.
CBD products derived from hemp are required by federal law to contain less than 0.3% THC, but quality varies widely. Products without third-party testing may contain more THC than the label states, and some owners unknowingly give their dogs products intended for human recreational use, which can contain significant THC.
If a dog ingests a large amount of a verified CBD product with a certificate of analysis showing 0% THC, the risk is limited to the mild, temporary effects described above. If the THC content is unknown or the dog shows severe neurological signs, that is a different situation and requires a vet call.
What should you do if your dog takes a large amount of CBD?
First, check the product label and any certificate of analysis to confirm the THC content. Note how many milligrams the dog likely ingested. If the product is verified 0% THC and the dog is alert enough to stand and walk, monitor at home. Keep the dog in a safe space away from stairs, pools, or other hazards where loss of coordination could cause injury. Offer small amounts of water. Do not try to induce vomiting unless a veterinarian instructs you to do so.
Call your vet or ASPCA Animal Poison Control at 888-426-4435 if the dog shows severe incoordination, tremors, pale gums, difficulty breathing, or if symptoms last longer than 12 hours. Also call if the THC content of the product is unknown, if the dog is very small, or if the dog has a pre-existing heart, liver, or kidney condition.
Be direct about what the dog ingested. Veterinarians cannot report you, and accurate information is necessary for proper care.
How long do the effects last?
Most side effects from high-dose CBD peak within one to two hours of ingestion and resolve within four to twelve hours as the compound clears the system. Larger doses or products with slower absorption may produce effects that last up to 24 hours, but the dog should show gradual improvement over that time. If symptoms are getting worse instead of better, or if the dog remains completely unresponsive beyond 12 hours, call your vet.
How do you avoid accidental high doses?
Store CBD products out of reach, the same way you would store any supplement or medication. Dogs are attracted to the smell of the carrier oils, and bottles with droppers are easy to chew through.
If you are starting CBD or adjusting the dose, go slowly. Most protocols recommend starting low and increasing gradually, which gives you a chance to see how the dog responds before reaching a higher dose. If you are unsure how much to give, check with your vet for guidance based on your dog's weight and condition.
Use products with clear labeling and third-party testing. A certificate of analysis tells you the actual CBD and THC content and confirms that the product matches the label. Products without testing may contain more or less CBD than stated, and THC contamination is more common in untested products.
What about cats?
This guide covers dogs only. Research on CBD safety in cats is extremely limited, and cats metabolize many compounds differently than dogs. Never assume that a dose or product safe for dogs is safe for cats.
