I Want to Drink Your Blood

I Want to Drink Your Blood refers to an unmarked and repeatable quest in Fallout 3.

Detailed walkthrough
After finishing Blood Ties, Vance will happily pay you 15 caps for every blood pack you bring him, even though you could have mentioned "donating" them in your conversation (you also had the choice to have Arefu sell them). No Experience Points or Karma bonus is granted. In order to sell blood packs to Vance you simply need to have them in your inventory when talking to him after Blood Ties is complete. An additional option to donate them should come up. Choose this and Vance will give you the appropriate value in caps in return.