When A survivor is Injured Or inflicted with Bleed, If V1 is next to them He will Regain 1 Hp point every second, He can Also get this from dead bodies, just not that frequently.

the main source of Gaining Blood Is through stunning the killer with the FEEDBACKER, Regaining HP For Stunning the killer. Although The amount of Blood Some killers Drop when stunned is Random, and it will be listed below:

Needlem0use: 4 HP

Tinky winky: 8 HP

Springtrap: 12 HP

Bon: 0 HP

Goji: 16 HP

The boiled one: 9 HP

SOMETHING: 1 HP

Nightmare: 0 HP

Jeff the killer: 15 HP

The Witch: 18 HP

Horror Sans: 0 (Horror sans cannot be stunned)

Mr L: 3 HP