What could cause someone to have a sudden blackout in vision?

What could cause someone to have a sudden blackout in vision? A great question from a Healthtap patient! Main causes of sudden black out: dehydration/illness, blood pressure drop, blood sugar drop (pre-diabetes/diabetes), vasovagal reaction,  blood flow issue in brain (from dehydration, sugar level change, tumor of some type, intracranial pressure increase), seizure, medications, anemia, transient […]