Fainting (also known as syncope) does occur in dogs but is less common than in people. Just like in people when a dog faints, it briefly loses consciousness and falls to the ground motionless but in most cases recovers within a few moments without treatment. It is important, but often difficult, to differentiate between fainting and fitting because the causes and treatments for the two conditions are very different. In addition, some other medical problems (for example, reduced blood levels of glucose, or certain diseases of the nerves and muscles) can cause episodes of weakness or collapse. If your dog collapses for whatever reason you should contact your vet immediately for further advice.