This syndrome has a history of developing rapidly. The symptoms may worsen up to 2 to 3 weeks after presentation to the point of complete paralysis and will then gradually improve over the next several weeks if the symptoms are mild. AIDP when severe can affect a patient's ability to breath on their own. Patients with severe AIDP may take up to 2 years to recover, and this recovery may not always be complete.

Treatment may shorten the course of the disease, but there is currently no known cure. Treatment may be in the forms of plasma exchanges, or intravenous immunoglobulin infusions. Some patients require life support and critical care hospitalization. 50% afflicted with AIDP will return to normal health 1 year after being diagnosed. After 3 years, almost one-third diagnosed will continue to have some weakness. Relapse occurs in only 3%. The percentage of people who die from AIDP is less than 5%.

Electrodiagnostic medicine is an important factor in diagnosing Guillain-Barré syndrome. EMGs can document that the impulses are blocked from activating the muscles. Nerve conduction studies (NCSs) can show that the time the nerve takes to respond to a signal is markedly slowed. It is important for the physician to perform these tests in the early stages of the syndrome in order to make an accurate diagnosis and begin therapy.