Fainting without warning can sometimes be an early symptom of a stroke. This occurs when the brain briefly loses its blood supply, even for just a few seconds. You might regain consciousness quickly, but that does not mean it is harmless. In some cases, fainting can be caused by a blockage or clot in a brain artery. If you or someone else passes out unexpectedly, especially if it is followed by weakness, confusion, or other stroke symptoms, seek medical help immediately.
