Blood pack

A blood pack is simply a pack of blood used for blood transfusions and, initially, is next to useless as a healing item as it only restores 1 HP per pack. In certain circumstances (see below) it can be increased to 20 HP per pack (only in Fallout 3). Blood packs, unlike other basic medicines and chems, have a weight of 1 unit each.

Locations
It can often be found in searchable first aid boxes, along with stimpaks, dirty water, purified water, and RadAway. First aid boxes are commonly found in bathrooms on the interior wall next to the door. Blood packs can also be found in searchable IV stands in hospitals and clinics.