Dogs shake for reasons ranging from completely harmless to genuinely urgent. The most common cause is simply being cold or excited, but shaking can also signal pain, poisoning, low blood sugar, or neurological disease. The key is context: a dog that shivers briefly after a bath is fine, while a dog that trembles for hours with no obvious trigger needs veterinary attention.
Cold and Hypothermia
The simplest explanation is temperature. Dogs shiver to generate body heat, just like humans. A normal canine body temperature sits between 100.5°F and 102.5°F, noticeably warmer than ours. When a dog’s internal temperature drops to around 98°F or 99°F, hypothermia begins to set in. The body responds by narrowing blood vessels near the skin, ears, and paws to protect vital organs, and shivering kicks in as a heat-generating reflex.
Small dogs, lean breeds, and dogs with thin coats lose heat faster. If your dog is shaking after being outside in cold weather or sitting on a cold floor, warming them up with a blanket or moving them to a warm room usually resolves it quickly. If the shivering doesn’t stop after warming, or your dog seems lethargic or unresponsive, that points to moderate or severe hypothermia, which requires immediate care.
Stress, Fear, and Excitement
Emotional shaking is extremely common. Many dogs tremble during thunderstorms, fireworks, car rides, or vet visits. This is an adrenaline response, not a sign of illness. You’ll usually see other stress signals alongside the shaking: panting, yawning, tucked tail, flattened ears, or hiding.
Some dogs also shake from pure excitement, like when you pick up the leash or when a favorite person walks through the door. This type of trembling is brief and stops once the dog calms down. If your dog shakes only in predictable, emotionally charged situations, it’s almost certainly behavioral rather than medical.
Pain
Dogs are notoriously good at hiding pain, and trembling is one of the subtle ways it shows. A dog dealing with abdominal pain, a joint injury, back problems, or internal discomfort may shake without limping or crying out. The shaking tends to be persistent rather than episodic, and you might notice other clues: reluctance to move, changes in posture, loss of appetite, or a tense abdomen. If your dog is shaking and seems “off” in ways you can’t pin down, pain is a strong possibility.
Low Blood Sugar
Hypoglycemia, or low blood sugar, causes trembling because the muscles and brain aren’t getting enough fuel. This is most common in toy breeds, puppies under four months old, and diabetic dogs on insulin. The shaking often comes with weakness, disorientation, or a wobbly gait. In mild cases, offering a small meal can help. But if the trembling is severe or your dog seems confused or unresponsive, this can progress to seizures quickly.
Low Calcium
Calcium plays a critical role in muscle function, and when levels drop too low, dogs develop tremors, muscle twitching, and spasms that can escalate to seizures. This most commonly affects nursing mothers in the weeks after giving birth, a condition called eclampsia. The body pulls so much calcium into milk production that blood levels plummet. It can also occur in dogs with certain metabolic disorders or after traumatic injury. A nursing dog that starts trembling, panting, or acting restless needs urgent veterinary attention.
Poisoning and Toxic Ingestion
Tremors are one of the hallmark signs of poisoning in dogs. Moldy food is an underrecognized culprit. When dogs get into compost bins, garbage, or moldy nuts, pasta, or dairy products, they can ingest toxins produced by mold. Symptoms appear within one to two hours and can range from fine muscle tremors lasting hours to days at lower exposures, to full seizures and death at higher doses.
Other common toxins that cause shaking include chocolate, caffeine, certain rodent poisons, and the sugar substitute xylitol. If you know or suspect your dog ate something toxic, or if shaking starts suddenly in an otherwise healthy dog that had unsupervised outdoor time, poisoning should be high on your list of concerns.
Generalized Tremor Syndrome
Some dogs develop whole-body tremors with no identifiable cause, a condition originally called “little white shaker syndrome” because it was first recognized in small, white-coated breeds like Maltese, West Highland White Terriers, and Bichon Frises. It has since been documented in dogs of all breeds, sizes, and coat colors, so the more accurate name is idiopathic generalized tremor syndrome.
The tremors affect the entire body and are present during waking hours. Dogs are typically otherwise alert and healthy. The condition responds well to treatment, and most dogs improve significantly within the first week or two. Diagnosis is made by ruling out other causes, including toxins, metabolic problems, and brain disease.
Neurological Disease
Shaking that comes with coordination problems, head tilting, circling, vision changes, or behavioral shifts can indicate disease in the brain or spinal cord. Canine distemper, a viral illness most common in unvaccinated dogs, causes localized involuntary twitching in the legs or face, along with weakness that often starts in the hind legs and progresses. As it advances, seizures become more frequent and severe, and some dogs develop compulsive behaviors like head pressing or continuous pacing.
Inflammatory brain diseases can also cause tremors alongside symptoms like loss of balance, seizures, neck pain, and changes in mental state. These conditions are diagnosed through a combination of imaging and spinal fluid analysis and require ongoing veterinary management.
Aging and Muscle Weakness
Older dogs commonly develop trembling in the hind legs. This can result from muscle loss, joint disease, or nerve degeneration. You might notice your senior dog’s legs shaking when standing still or after moderate exercise. Muscle fatigue sets in faster in aging dogs, and weakened joints demand more effort to stabilize. This type of shaking is usually gradual in onset and tends to worsen slowly over months. While it’s not typically an emergency, it does warrant a vet visit to assess for treatable causes like arthritis.
When Shaking Is an Emergency
Most shaking in dogs is benign, but certain combinations of symptoms signal a true emergency. Get to a vet immediately if your dog’s shaking is accompanied by seizures, collapse or inability to walk, difficulty breathing, profuse vomiting or diarrhea, a swollen or painful abdomen, extreme weakness or pale gums, known or suspected toxin ingestion, or severe changes in consciousness. Shaking that starts suddenly in a previously healthy dog, lasts more than an hour without an obvious emotional trigger, or gets progressively worse also warrants prompt evaluation.
If the shaking is mild, your dog is eating and drinking normally, and there’s an obvious explanation like cold weather or a stressful event, it’s reasonable to monitor at home. But when in doubt, a vet visit gives you a clear answer and catches serious problems early.