Blood is a specialized bodily fluid that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells. Vampires feel an overwhelming need to drink human blood. Their thirst is only satisfied by indulging in it; generally vampires are less bloodthirsty after drinking. It is however more difficult to abstain from it in the future as this is the case with Eric and Michael. Vampires usually move around alone or with a mate. The vampires diet is reflected in the color of their eye: electric blue for the immortals of the original congregation, sterling gold for hybrids, crimson red for those who feast on human blood, gold for those who drink animal blood, burgundy for those living on a mixed diet and essential silver for the impending species of tribrids. Black eyes denote a hungry vampire independently from their diet. Abstinence from human blood helps vampires relate to other vampires and form bonds with them because it makes them less animalistic. The strength of a vampire is also affected by the amount of human blood in their system. If a vegetarian were to drink from a single human, their strength would only increase fractionally. As newborns still retain the human blood they had when they were human; they are much stronger than older vampires. It takes about a year before both blood and strength decrease to their definitive levels. The blood of each human has an individual taste and smell; sometimes a vampire finds a human whose blood he or she finds absolutely irresistible.
- Electric Blue for the original congregation of vampires.
- Red for those who consume on human vital fluid.
- Gold for those who consume the vital fluid of animals.
- Burgundy for those living on a mixed diet.
- Sterling Gold for the species of hybrids.
- Essential Silver for the species of tribrids.
Vampires can smell blood from far away and follow its scent, particularly if it has been spilled. Most vampires find it impossible to resist it when a human begins to bleed and as a result it is very difficult for a vampire to stop drinking once started. It is somewhat easier when the vampire is a vegetarian; particularly if he or she has been for a long time. Trinity is the epitome of this characteristic; she is shown to be completely capable of suppressing this urge.
Most of the vampires drink human blood. Besides humans, witches also have human blood and can also be drunk by vampires. Some vampires drink blood from vital fluid dispensers but others either kill the human to feed or leave them alive in order to compel them. When a vampire smells blood, their face starts showing veins around there eyes and their fangs lengthen. Using human blood makes vampires considerably more stronger than ones who drink animal blood in order to have their abilities at their best. Feeding on human blood completes the final phase in transitioning into becoming a vampire. If an individual chooses not to feed and resists human blood, the transition will not complete and the individual will die. However, the urge for human blood is a crucial aspect of life as a vampire. The bloodlust and hunger becomes as constant as breathing and every individual must learn to adjust to the lifestyle. When a vampire experiences moments of hunger, bloodlust or other heightened emotions; their vampirism becomes evident in facial changes as their eyes redden, veins around their eyes darken and protrude and their fangs become exposed. The majority of vampires drink human blood. Some choose to acquire vital fluid dispensers to satisfy their consumption requirements. Others either consume the vital fluid of willing or compelled individuals or simply feed and kill their prey. Animal blood does not provide the same level of nourishment to vampires as human blood does. Human blood makes a vampire considerably stronger than those who drink animal blood; keeping their strength and abilities at their peak. It is shown that the blood of witches seems to have the same effect on vampires as human blood. As werewolves attack any creature on sight, they will most likely attack a witch if they cross paths and consume their blood as well. It is shown that the vital fluid of witches can be used to complete a transition into a vampire as a substitute for normal human blood.
Animal blood comes from animals whom are eradicated for nourishment. Some vampires drink animal blood as they are classified as vegetarians. Vampires that drink animal blood have decreased strength and some of there abilities might not work as best as it could drinking human blood. An example of this is that compulsion might not work right or not work at all. To get animal blood, the vampire has to go out in the woods and hunt animals.
It is much harder for a vampire to bleed compared to a human because of their increased strength and invulnerability. A vampire can bleed like a human but it requires much more force to damage them; besides using one of their weaknesses. If they are unable to get attacked through there weaknesses, they will heal rapidly if not instantly. To transform a human into an immortal, the vampire must be required to extract venom from their glands which will consolidate throughout the entire anatomy of a human. Once the transition has concluded, the newborn is required to feed upon human vital fluid.
It is confirmed that vampires can consume the vital fluid of werewolves. Before werewolves transform, they do bleed normally like a human does. In regards to werewolves, it is harder to damage them but how hard it is to damage them is currently unknown.
The blood of hybrids can cure a werewolf bite as the venom from their glands can create more absolute hybrids.