If someone vomits some blood but had a normal upper endoscopy. what else could it be?

Small tear: In a young man if blood with vomiting and negative egd- there is possibility you had a tear that may have healed by the time you had test. If there are no varices that are swollen blood vessels in the esophagus.

Possible: Minor erosions or small ulcers that are not actively bleeding or bleeding from respiratory tract could be mistaken for vomiting blood.

Lot of possibilities: One should evaluate the possibility of a Mallory Weiss tear which is small tear in esophagus followed after severe dry heaves, wrenching, and vomiting; ENT causes as we'll should be considered