Rat terriers shake for a wide range of reasons, from being cold or excited to genuine medical concerns like low blood sugar or anxiety disorders. Most of the time, the shaking is harmless and tied to their small body size, high energy temperament, or emotional state. But persistent or sudden shaking can signal something that needs attention, so understanding the different causes helps you figure out when to relax and when to act.
Small Bodies Lose Heat Fast
The most straightforward explanation is temperature. Rat terriers are lean, low-body-fat dogs that typically weigh between 10 and 25 pounds. That combination of small size and thin build means they lose body heat quickly. If your rat terrier shakes after going outside on a cool day, during air-conditioned summers, or while sleeping on a tile floor, cold is the likely culprit. A dog sweater or warm blanket solves this one easily.
Excitement and High-Energy Temperament
Rat terriers are famously energetic, alert dogs bred for hunting and farm work. That wired temperament means they often tremble when they’re excited, whether you’ve just come home, they see a squirrel, or dinner is being prepared. This type of shaking is brief, happens in obvious emotional contexts, and stops once the dog settles. It’s completely normal and doesn’t need any intervention.
Anxiety and Stress-Related Shaking
Terrier breeds tend to be sensitive and reactive, which makes them prone to anxiety-driven trembling. Thunderstorms, fireworks, separation from their owner, unfamiliar environments, and car rides are common triggers. The shaking is often accompanied by panting, pacing, whining, or hiding.
Pressure wraps (like the Thundershirt) are a popular option for anxious dogs. One study on dogs with thunderstorm phobia found a significant decrease in both pacing and shaking when dogs wore a snug vest, and a separate study that included terrier breeds showed dogs wearing a tightly fitted vest had a smaller increase in heart rate during stressful separation compared to dogs without one. That said, a systematic review of the available research concluded the overall evidence for pressure wraps is still limited and inconsistent. They’re worth trying, but they may not work for every dog, and severe anxiety often benefits from behavioral training or veterinary guidance.
Low Blood Sugar in Small Breeds
Hypoglycemia, or low blood sugar, is a real risk for small dogs like rat terriers, especially puppies and young adults. Blood sugar below about 40 to 50 mg/dL typically triggers visible symptoms: muscle tremors, weakness, wobbliness, nervousness, and in severe cases, collapse or seizures. The body’s stress response kicks in too, causing restlessness, rapid breathing, and a racing heart.
Toy and miniature breeds are at higher risk because their low body mass makes it harder to maintain stable glucose levels, particularly if they skip a meal, exercise heavily, or are stressed. Puppies are especially vulnerable. If your rat terrier shakes and also seems weak, uncoordinated, or unusually lethargic, low blood sugar is worth considering. Feeding smaller, more frequent meals throughout the day can help prevent dips. If you suspect a hypoglycemic episode, offering a small amount of food or a sugar source and getting to your vet promptly is the right move.
Aging and Senile Tremors
Older rat terriers commonly develop a progressive limb tremor, particularly in the hind legs. This condition, sometimes called benign idiopathic rapid postural tremor or senile tremor, has been observed specifically in terrier breeds. Researchers studying the phenomenon in one terrier recorded involuntary muscle discharges at about 3 cycles per second while the dog was standing. The tremor looks like a fine, rhythmic shaking in the legs, most noticeable when the dog is standing still and absent when lying down or asleep.
This type of tremor doesn’t require treatment. It doesn’t appear to cause pain and doesn’t progress into something more serious. It’s considered the dog equivalent of essential tremor in older humans. If your senior rat terrier’s legs shake when standing but they’re otherwise eating, walking, and behaving normally, age-related tremor is the most likely explanation.
Generalized Tremor Syndrome
Sometimes called white shaker disease (because it was first identified in small white-coated breeds), generalized tremor syndrome can affect dogs of any color or breed. It typically shows up in young dogs, with a median onset around 2 years old. The hallmark is whole-body trembling that may worsen with intentional movement, like when the dog tries to focus on something or reach for food. Other signs can include head tilting, loss of balance, eye twitching, reduced appetite, and lethargy.
This condition involves inflammation in the central nervous system and responds well to corticosteroid treatment. If tremors don’t improve within the first 48 hours on their own, that pattern strongly suggests generalized tremor syndrome rather than something that will resolve by itself. Most dogs improve significantly with treatment.
Toxin Exposure
Sudden, unexplained shaking in a previously calm dog can indicate poisoning. The ASPCA lists caffeine and xylitol (a sweetener found in sugar-free gum, candy, peanut butter, and baked goods) among the most common household substances that cause tremors in dogs. Chocolate, certain medications, rodent poison, and some plants can also trigger muscle tremors. If the shaking started abruptly and your dog may have gotten into something, treat it as urgent.
Shaking vs. Seizures
One of the most important distinctions for any dog owner is telling apart regular shaking from a seizure. During a seizure, dogs typically collapse or fall to one side, stiffen their body, and jerk or kick their legs rhythmically. They may lose consciousness, foam at the mouth, lose bladder or bowel control, or chomp their jaws. A focal seizure can be subtler, affecting only the face, one limb, or one side of the body.
Normal shaking happens while the dog is conscious and responsive. They can stop, look at you, walk, and interact. Seizures render the dog unresponsive for the duration, and afterward the dog often appears confused, unsteady, or dazed for minutes to hours. Most seizures end within two to three minutes. If one lasts longer than five minutes, involves multiple episodes in a row, or your dog has three or more seizures within 24 hours, that’s an emergency requiring immediate veterinary care.
Patterns Worth Watching
Context is everything when evaluating your rat terrier’s shaking. Shaking that happens only when it’s cold, during storms, or at mealtimes has an obvious, benign explanation. Shaking that persists at rest, worsens over days, accompanies other symptoms like vomiting or stumbling, or starts suddenly without a clear trigger deserves a closer look. Keeping a mental note of when the shaking happens, how long it lasts, and what else is going on gives your vet the most useful information if you do need to bring your dog in.