Dogs shake for a wide range of reasons, from entirely harmless to genuinely urgent. The first job is to work out which category you are in.

Harmless reasons

Cold. Small breeds, thin dogs, short coated dogs and puppies lose heat quickly. Shivering that stops once the dog is warm and dry is exactly what it looks like.

Excitement or anticipation. Common before a walk or at feeding time, and it stops as soon as the event happens.

Fear and stress. Fireworks, thunder, the car, the clinic. Usually with other signs: tucked tail, flattened ears, panting, lip licking, hiding.

Muscle fatigue after unusually hard exercise, which settles with rest.

Old age. Mild tremor in the hind legs is common in older dogs, often related to muscle loss and arthritis.

Reasons that need attention

Pain. One of the most common causes and one of the most missed. Back pain and abdominal pain in particular produce trembling, often with a hunched posture, reluctance to move or jump, and a tense abdomen.

Poisoning. Several toxins cause tremors: chocolate, xylitol, some mushrooms, mouldy food, slug pellets, permethrin, and certain human medications. Tremors after eating something unknown are an emergency.

Low blood sugar. Particularly in puppies, toy breeds and diabetic dogs. Trembling, weakness, disorientation and eventually collapse. This moves fast.

Kidney disease, which produces tremors as toxins accumulate.

Fever and infection.

Neurological disease, including inflammatory conditions of the brain.

Tremor or seizure

The distinction matters, so look for these:

A tremor leaves the dog conscious and aware. It can respond to you, and the shaking usually stops if you distract it or change its position.

A seizure involves loss of awareness. The dog does not respond, may fall on its side and paddle, may drool, urinate or defecate, and afterwards seems dazed and disoriented for minutes to hours.

If it is a seizure, do not put your hands near the mouth. Clear hard objects away, dim the light, time it, and come in. A seizure lasting more than five minutes, or repeating, is an emergency.

What to do

Warm the dog and dry it if cold seems likely, and see whether the shaking stops. Check the gums; pale, white or blue gums are urgent.

Do not give any human medication. Do not offer food if the dog is not fully alert.

Film the episode if you can. It is often the single most useful thing you bring to the consultation.

When to come in

Shaking that does not stop when the dog is warm and calm. Shaking with vomiting, diarrhoea, unsteadiness, confusion or weakness. Any suspicion of something eaten. A hunched posture or a tense abdomen. Shaking in a puppy or a diabetic dog. Or anything that looks like a seizure.