A dog’s heart can beat fast for reasons ranging from totally normal (excitement, exercise, heat) to potentially serious (pain, heart disease, poisoning). The first step is knowing what “fast” actually means for your dog’s size. Small dogs normally have a resting heart rate of 90 to 120 beats per minute, medium dogs fall between 70 and 110, and large dogs run 60 to 90. If your dog’s heart rate at rest consistently exceeds those ranges, something worth investigating is going on.
How to Check Your Dog’s Heart Rate
Lay your dog on their right side. Place your hand on the left side of the chest where the elbow meets the ribcage, roughly over the fifth rib. You should feel a heartbeat against your palm. Count the beats for 15 seconds, then multiply by four to get beats per minute. Do this when your dog is calm and resting, not right after a walk or a bout of zoomies. A single reading can be misleading, so check a few times over the course of a day to see if the pattern holds.
Puppies naturally have faster heart rates than adult dogs, sometimes up to 220 beats per minute in very young pups. This slows as they mature. If you have a puppy and the rate seems alarmingly high, age is likely the explanation, but a vet can confirm.
Normal Reasons for a Fast Heartbeat
Exercise, excitement, stress, and heat all temporarily raise heart rate. If your dog just sprinted across the yard, greeted a visitor at the door, or spent time in the sun, a pounding heart is the body doing exactly what it should. The key word is “temporarily.” A healthy dog’s heart rate returns to its normal resting range within a few minutes of calming down. If it stays elevated for 20 or 30 minutes after the stimulus is gone, that’s when it becomes a clue that something else is happening.
Fear and anxiety also drive heart rate up. Thunderstorms, fireworks, car rides, and vet visits can all trigger the same adrenaline response that exercise does. You’ll usually see other signs at the same time: panting, pacing, trembling, or hiding.
Pain as a Hidden Cause
Heart rate and breathing rate are often the first two vital signs to climb when a dog is in pain. Dogs are notoriously good at masking discomfort, so a fast heart rate at rest may be one of the earliest clues that something hurts. Acute pain, like a broken nail or a muscle injury, triggers a burst of adrenaline that pushes the heart rate up quickly. Dogs in acute pain also tend to pant heavily.
Chronic pain works differently. Ongoing conditions like arthritis or dental disease keep stress hormones like cortisol and adrenaline elevated around the clock. Over time, this raises both resting heart rate and resting breathing rate. If your dog’s heart seems to beat faster than it used to and you can’t pinpoint a reason, undiagnosed pain is worth considering, especially in older dogs.
Heart Disease and Other Medical Causes
Several medical conditions cause a persistently fast heart rate. Heart disease is the most direct. When the heart isn’t pumping efficiently, whether from a leaky valve, an enlarged chamber, or an irregular rhythm, it compensates by beating faster. Small breeds are especially prone to a condition where one of the heart’s valves gradually degenerates, forcing the heart to work harder over time. Large and giant breeds are more susceptible to a condition where the heart muscle itself weakens and stretches.
Beyond the heart itself, anemia (too few red blood cells) forces the heart to beat faster to deliver enough oxygen. Fever from an infection does the same. Hyperthyroidism, though far more common in cats, can occasionally affect dogs and raises heart rate. Dehydration reduces blood volume, so the heart speeds up to maintain circulation. Even an overactive adrenal gland can flood the body with stress hormones that keep the heart racing.
Toxins That Speed Up the Heart
If the fast heartbeat came on suddenly, think about what your dog may have gotten into. Several common household items cause a rapid heart rate in dogs:
- Asthma inhalers. Dogs that puncture or chew on an albuterol inhaler can absorb a massive dose. This causes a racing heart, agitation, panting, tremors, and weakness.
- Human medications. Antidepressants, anti-anxiety pills, and decongestants are frequently chewed out of purses or off countertops. Many of these drugs cause a fast or irregular heartbeat in dogs even at small doses.
- Caffeine and chocolate. Both contain stimulants that directly increase heart rate. Dark chocolate and espresso beans carry the highest risk.
If you suspect your dog ingested something toxic, don’t wait for symptoms to worsen. Bring the packaging with you so the vet knows exactly what they’re dealing with.
Warning Signs That Need Immediate Attention
A fast heartbeat on its own isn’t always an emergency, but paired with certain other symptoms, it becomes urgent. Watch for these red flags:
- Pale, blue, gray, or white gums. Normal gums are pink. Color changes signal that oxygenated blood isn’t reaching the tissues properly, which can mean shock, anemia, or circulatory failure.
- Labored breathing or gasping. Noisy breathing, wheezing, or a dog that seems to struggle for air alongside a fast heart rate points to a cardiovascular or respiratory crisis.
- Sudden bloating with retching. A swollen, hard abdomen combined with unsuccessful attempts to vomit and a racing heart can indicate gastric torsion, a life-threatening condition where the stomach twists on itself. Large, deep-chested breeds are most at risk.
- Collapse or extreme weakness. A dog that can’t stand, staggers, or becomes unresponsive needs emergency care immediately. These signs often indicate dangerously low blood pressure or a severe heart rhythm problem.
- Disorientation or unresponsiveness. If your dog doesn’t respond to your voice or seems mentally “checked out,” something serious is affecting blood flow to the brain.
What to Track Before the Vet Visit
If the situation isn’t an emergency but the fast heart rate concerns you, gathering a few details before calling your vet makes the conversation more productive. Note your dog’s resting heart rate at a few different times of day. Write down any other changes you’ve noticed: appetite shifts, coughing (especially at night), exercise intolerance, restlessness, or changes in breathing. Note whether the fast heart rate started suddenly or has been building over weeks.
A vet will typically listen to the heart with a stethoscope, looking for murmurs or irregular rhythms. From there, they may recommend an electrocardiogram to map the heart’s electrical activity or an echocardiogram (an ultrasound of the heart) to visualize how well it’s pumping. Blood work can rule out anemia, infection, thyroid problems, and organ dysfunction. These tests are straightforward and usually don’t require sedation.
Many causes of a fast heart rate in dogs are highly treatable once identified. Heart conditions can often be managed with medication that keeps a dog comfortable for years. Pain can be addressed. Toxin exposures, caught early, have good outcomes. The heart rate itself is a signal, not a diagnosis, and the most useful thing you can do is pay attention to it.