Repeated studies on cannabidiol (CBD) have shown it to be one of the safest, most compatible, and least toxic treatments available right now. It is unlikely to cause adverse reactions or dependency in either humans or animals.

There are of course exceptions to every rule, and it should be noted that extremely high doses of CBD have shown adverse effects in some tests (more on that below).

In general, CBD products for dogs fair very well when compared to many of the other drugs and treatments traditionally offered to dogs and their owners.

Here’s the rundown on possible side effects of canine CBD usage, as well as the potential risks of more traditional CBD alternatives.

CBD (Cannabidiol)

CBD is a cannabinoid—a class of substances that interact with the body via the endocannabinoid system. Unlike opioids and other pharmaceutical drugs, interaction with this system means that CBD doesn’t directly affect the brainstem or areas controlling respiration.

In terms of substance safety, this is a big plus, meaning that serious overdoses from CBD are very rare.

Also in CBD’s favor is its half-life, which is less than 12 hours for most dogs. A half-life of this duration means that dosages from the previous day shouldn’t negatively interact with the current day’s dose, adding to user confidence.

Finally, CBD is one of the many non-psychoactive cannabinoids derived from the cannabis plant, meaning that—when property isolated—CBD should have zero intoxicating effect. While CBD’s ability to reduce anxiety and inflammation is likely to induce a sense of relaxation, this certainly isn’t the psychedelic high most associate with weed. In fact, most CBD products for pets are produced from the hemp plant, not the marijuana plant, which means there’s a minimal presence of the high-causing cannabinoid, THC, to begin with.

Cannabis in the defocus with the image of the formula CBD

Possible side effects

Nevertheless, more minor side effects have been reported by some people and dogs. It’s not exactly clear why some experience these negative effects and others don’t, but researchers believe it may be down to a combination of high (or prolonged) dosage, genetic disposition, and CBD that has a low purity or is poorly produced.

If your dog does experience CBD side effects, they are likely to include:

  • Sleepiness, fatigue, or lethargy

  • Urinary incontinence

  • Vomiting

  • Ataxia (coordination issues / drunkenness)

  • Hyperesthesia (hyper-sensitivity / overwhelming sensations)

Side effects of CBD alternatives

Many owners turn to CBD because they’re unsatisfied with pharmaceutical medications prescribed by vets. Others are looking to recreate the benefits of drugs such as nonsteroidal anti-inflammatories (NSAIDs) which are often unsafe for dogs to take.

Because of this, it’s important to weigh the possible side effects of CBD against any risks and symptoms associated with dogs and other courses of drugs. Let’s take a look at some of the most common canine side effects reported with these CBD alternatives:

NSAIDs (Anti-inflammatory drugs)

Both NSAIDs and CBD effectively reduce inflammation in dogs. NSAID’s are commonly prescribed treatment for pain due to injury, surgery, or chronic conditions such as arthritis. Not all NSAIDs are safe for dogs, requiring the FDA to monitor and approve certain active ingredients.

Possible side effects
NSAIDs can be harsh on the digestive systems of both humans and dogs, but dogs are particularly vulnerable to GI side-effects such as vomiting, lack of appetite, and diarrhea. Adverse effects can become far more serious when dogs are given NSAIDs designed for human consumption, such as aspirin, ibuprofen, and naproxen—which may result in liver and kidney damage. So, never give you dog non-pet approved medication without first consulting your vet.


Dogs as a species are prone to compulsive and neurotic behaviors, with some breeds particularly vulnerable to anxiety. As a result, many dogs have benefited from medications from mild sedatives or drugs that increase the level of serotonin in the body. The FDA has approved several antidepressant drugs for use in treating canine mental health, including clomipramine and dexmedetomidine, most often for separation anxiety.

Possible side effects
Depending on the category of antidepressant taken, dogs may become less alert, less willing to engage in play or socialization, and find it harder to transition between sleep and waking states. More seriously, serotonin syndrome is a risk for anyone using anti-anxiety medication for a prolonged period. Serotonin syndrome occurs when high levels of the neurotransmitter accumulate inside the body, and can cause shivering, fever, and issues with muscle function.


Opioids such as morphine and tramadol are often used inside the veterinary surgery, where they’re considered highly effective as a temporary treatment for acute pain. However, opioid drugs are also prescribed for home use by some veterinarians, which has led to a questioning of the efficacy of opioids as a widespread outpatient treatment.

Possible side effects
As with humans, opioids have the disadvantage of being tolerance-forming, leading to the need for higher dosages in order to maintain effectiveness. When dogs experience toxic doses of opioids, adverse effects can include pinpoint pupils, lethargy and drunkenness, and slowed breathing. Respiratory depression is the most serious common side effect of opioid use, which is classified as the slowing of the breathing cycle to the point where oxygen and carbon dioxide are not being processed by the body.

Anti-seizure medication

The majority of treatment courses for dogs experiencing repeated seizures include the use of phenobarbital and potassium bromide, though some dogs will only respond diazepam when given on a reactive basis.

Possible side effects
Common side effects of phenobarbital include sedation and lack of coordination. Potassium bromide, on the other hand, has been known to cause rear limb weakness in rare cases.

THC (Tetrahydrocannabinol)

Unlike CBD, THC is a psychoactive cannabinoid, which means it’s responsible for creating the high or stoned feeling that is traditionally associated with cannabis. While full-spectrum CBD oils for dogs will contain trace amounts of THC safe for dogs, human CBD products or cannabis is toxic to dogs.

Possible side effects
THC should never be given to dogs. While trace amounts are found in some CBD products, anything higher can cause pups to become disorientated, uncoordinated, or hyperactive. Pupils may dilate, and drooling may occur. Though rare, more serious reactions have been reported, including slowed breathing, reduced body temperature, tremors, and seizures.


  • Some side effects and toxicity levels have been identified in CBD usage among dogs. While rare, the most commonly reported symptoms include lethargy, sleepiness, vomiting, and diarrhea.

  • Compared to alternative drugs and treatments, CBD is often a safer, more stable option. That said, research is still ongoing on how CBD interacts with other drugs. Because of this, combining treatments should only be done in consultation with a veterinarian.

  • NSAIDs, anti-depressants, opioids, and anti-seizure medication can all be dangerous drugs in the wrong circumstances. Whenever your dog begins a course of medication, be sure to follow professional recommendations and closely observe how your dog reacts.

  • Dogs should never be given THC in any amount, other than the tiny levels found in some CBD products.