Causes of Fainting in Dogs

Fainting in dogs, or canine syncope, occurs when your dog loses consciousness briefly due to lack of oxygen to the brain. Your dog may collapse for seconds or minutes. Most cases of fainting spells in dogs are the result of low blood pressure cerebral hypoxia, lack of oxygen delivery to the brain. Syncope is a symptom of illness; it's not considered an illness in itself.

Causes of Fainting in Dogs

Syncope, or dog fainting, can occur in any dog of any age or breed. It's a symptom of illness that's usually related to neurological or neuromuscular disease, metabolic disorder, stroke, heart disease or bone disease. Dog fainting may be the result of disorders like epilepsy, or of conditions like narcolepsy or cataplexy. There are dozens of diseases and conditions that can cause dog fainting. Some of the most common include:

  • Hepatic encephalopathy, a disturbance in brain function caused by liver disease or deformity of the liver
  • Hypocalcemia, or low blood calcium levels
  • Hypoglycemia, or low blood sugar
  • Drug reaction
  • Neuromuscular diseases like myotonia congenita or myasthenia gravis
  • Hypokalemia, or low blood potassium levels
  • Endocrine disorders like Addison's Disease or Cushing's Disease

Diagnosing the Cause of Fainting in Dogs

Dog fainting is not an illness in itself, but a symptom of something more serious. Your vet will need a complete medical history and a thorough physical exam to diagnose the cause of your dog's fainting spells. You can help your vet by providing certain information.

If your dog suffers from a fainting spell of any sort, make a note of when the fainting spell occurred and the circumstances in which it occurred. Your vet will want as many details of the event as you can manage to provide.

Do your best to describe for your vet, in detail, the episode of fainting. Tell your vet how the fainting spell began, what your dog was doing at the time, where he was doing it, what other symptoms occurred simultaneously and how long the fainting spell lasted.

If your dog was moving, exercising or excited, tell your vet. If your dog's tongue and mucous membranes changed color at all, tell your vet. If your dog was coughing before the fainting spell began, tell your vet. Also tell your vet if your dog's fainting spell was accompanied by physical movements like leg paddling. Make a note of any abnormal behavior that may occur before or after the fainting spell.

Pay attention to your dog's level of energy and interest in activities. Pay attention to your dog's appetite and thirst levels, as well as his ability to breathe normally. Measure your dog's heart beat during the fainting spell by counting how many times his heart beats over a 15 second period.

Treating Fainting in Dogs

Your vet may need to perform a range of tests, including blood work, X-rays and EKGs, in order to make a proper diagnosis of the cause of your dog's fainting spells. Treatment will depend on the cause of your dog's fainting spells.