Lifegiver/J.E. Sawyer's Fallout RPG
With each level of this Perk, you gain an additional 4 Hit Points. This may not seem like a lot, but every little bit helps.
With each level of this Perk, you gain an additional 4 Hit Points every time you advance a level. This is in addition to the hit points you already gain per level based off of your endurance.”— Fallout and Fallout 2 description
+4 hit points per level gained (+8 with both ranks).