Doctor's Notes on Fainting
Fainting, or “passing out,” is medically known as syncope. It is the result of becoming unconscious, and this is always abnormal and may be a sign of a life-threatening condition. Fainting can have a number of causes, including decreased blood flow to the brain due to heart failure or low blood pressure, anemia, dehydration, vasovagal syncope, and abnormalities of the heart or heart valves.
Signs and symptoms associated with the period immediately before fainting include lightheadedness, dizziness, feeling fatigued or weak, nausea, sweating, tingling sensations, muffled hearing, and vision disturbances. Other symptoms and signs that may occur are related to the specific cause of fainting and can include chest pain, shortness of breath, dry skin, reduced urine output, vomiting, diarrhea, or excess urination.
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.