Dogs that have ingested drugs typically show sudden, dramatic changes in behavior and coordination that don’t match any known illness or injury. The specific signs depend on what your dog got into, but the most common red flags fall into a few recognizable patterns: extreme sedation or hyperactivity that came on within minutes to hours, a staggering “drunken” walk, unusual eye changes, and loss of bladder control. Knowing which symptoms point to which type of substance can help you act fast and give your vet the information they need.
Signs of Marijuana or THC Exposure
Cannabis is one of the most common drug exposures in dogs, especially as edibles become more widespread in homes. The hallmark signs are urinary incontinence (your dog dribbling urine without seeming to notice), disorientation, a wobbly “drunken” gait, lethargy, heightened startle responses, and a low heart rate. Your dog may look glazed over, sway while standing, or seem unable to figure out where they are. Many owners describe their dog acting like they’re half asleep but flinching at every sound or touch.
Symptoms from edibles usually appear within 30 minutes to a couple of hours after ingestion. At higher doses, dogs can develop eye tremors (the eyes flicking back and forth), agitation, rapid breathing, a fast heart rate, and even seizures. While the lethal dose of THC is extremely high, over 3 grams per kilogram of body weight, concentrated products like THC butter used in medical-grade edibles have been linked to deaths. The danger isn’t the plant material itself so much as the potency of modern edible products.
Signs of Stimulant Ingestion
If your dog got into a stimulant, such as amphetamines, ADHD medication, methamphetamine, or cocaine, the picture looks very different from cannabis. Instead of sedation, you’ll see a dog that’s wired. A rapid heart rate is present in virtually every case. Hyperactivity shows up in about 95% of affected dogs, and tremors or muscle twitching in about 85%.
The timeline varies by substance. Cocaine acts fast, producing symptoms within 10 to 15 minutes. Amphetamines and methamphetamine take longer, peaking one to three hours after ingestion. MDMA (ecstasy) falls somewhere in between, with signs developing within 30 minutes to two hours. Beyond the core triad of rapid heart rate, hyperactivity, and tremors, dogs may also pant heavily, pace restlessly, or have dilated pupils. In severe cases, body temperature spikes dangerously high, and seizures can follow.
Signs of Opioid Exposure
Opioids produce a distinct set of symptoms that look almost opposite to stimulants. The classic sign is extreme sedation: your dog may be nearly impossible to wake, limp, and barely responsive. Breathing becomes slow and shallow, which is the most dangerous part of opioid exposure.
One telling physical sign is the pupils. Opioids cause the pupils to constrict into tiny pinpoints, even in dim lighting. This happens because these drugs directly increase the firing rate of the brain cells that control pupil constriction. If your dog is profoundly sedated with pinpoint pupils, opioid exposure should be high on your list of concerns. The combination of slowed breathing and deep unresponsiveness can become life-threatening quickly.
Signs of Antidepressant or Prescription Drug Ingestion
Human antidepressants, particularly SSRIs and similar medications, are among the most frequently ingested prescription drugs in dogs simply because they’re so common in households. When a dog eats enough of these pills, they can develop serotonin syndrome, a condition caused by a dangerous excess of the brain chemical serotonin.
The signs of serotonin syndrome include agitation, restlessness, dilated pupils, a rapid heart rate, fever, muscle tremors or jerking, difficulty walking, disorientation, vocalization (whining or crying), and in severe cases, seizures. It’s a distinctive combination: your dog seems simultaneously overstimulated and uncoordinated, often trembling and vocalizing while struggling to walk normally. This is a veterinary emergency.
Signs of Hallucinogen Exposure
Dogs that ingest hallucinogens like psilocybin mushrooms or LSD can be particularly distressing to watch because they appear frightened and confused. Symptoms from mushrooms typically start within 30 minutes to an hour, though they can be delayed up to three hours. LSD symptoms usually appear within 90 minutes and can last up to 12 hours. Affected dogs may vocalize, startle at nothing, act fearful or aggressive without cause, lose coordination, and seem to track things that aren’t there.
How Vets Confirm Drug Exposure
If you bring your dog to the vet with suspected drug exposure, they won’t rely solely on physical symptoms. Veterinarians can use human over-the-counter urine drug test kits on dogs, and these produce results in minutes. Research at Kansas State University confirmed that these rapid kits reliably detect amphetamines, methamphetamines, barbiturates, opiates, and benzodiazepines in canine urine.
The kits have a significant blind spot, though. They are unreliable for detecting THC, cocaine, and PCP in dogs. Neither the rapid kits nor the gold-standard lab test (gas chromatography/mass spectrometry) was effective at identifying marijuana in dogs with known exposure. This means a negative drug test does not rule out cannabis ingestion. Your vet will likely diagnose THC exposure based on your dog’s symptoms and history rather than a test result.
The gold-standard lab testing is highly accurate for the substances it does detect, but it’s expensive and slow, making it impractical in an emergency. For most situations, the rapid urine test combined with your vet’s clinical judgment is enough to guide treatment.
What to Do If You Suspect Drug Exposure
Speed matters. If your dog is having seizures, is unresponsive, or is breathing very slowly, go directly to an emergency veterinary clinic. For situations where your dog is showing symptoms but is conscious and breathing adequately, call one of the two major poison control hotlines for animals before you drive anywhere. The Pet Poison Helpline (855-764-7661) and the ASPCA Animal Poison Control Center (888-426-4435) both charge a fee, but the specialists on these lines can tell you exactly what level of care your dog needs based on the substance, the amount, your dog’s size, and when the exposure happened.
Be honest with your vet about what your dog may have ingested. Veterinarians are not obligated to report drug use, and withholding information wastes precious time. If you aren’t sure what your dog ate but you found a chewed-up bag, a torn wrapper, or a suspicious substance, bring it with you. The more specific you can be about the substance and the timing, the faster your vet can act. For stimulants and opioids in particular, the window between “manageable” and “critical” can be narrow, and the right treatment given early makes a significant difference in outcome.