Cold, fear, and excitement
Small, thin-coated, wet, or chilled dogs may shiver to generate heat. Fear and adrenaline can also cause trembling. These explanations are more likely when the trigger is obvious and the dog otherwise behaves normally.
Pain and nausea
Dogs in pain may tremble, pant, avoid movement, or adopt an unusual posture. Nausea can cause shaking along with lip licking, drooling, restlessness, or vomiting.
Metabolic and toxic causes
Low blood sugar is especially important in very small puppies and diabetic dogs receiving insulin. Some toxins and medications can cause tremors or seizures. Bring packaging or a photo of any possible exposure.
Shaking versus a seizure
A trembling dog is usually conscious and responsive. During a generalized seizure, consciousness is altered and there may be rigid or paddling movements, jaw activity, salivation, or loss of bladder control. Video is useful if it can be recorded safely.