I made a couple changes to get the biology correct. Thanks, Lucas.

I am working on a story where vampires have a biological, rather than mystical, reason to take the blood of others. They cannot produce their own heme (a hemoglobin precursor) - similar in some ways to a person suffering from porphyria. If they go for long periods without some blood intake they will have symptoms like those of iron-deficiency anemia and will eventually die.

I know that there are "vampire" bats that drink the blood of other animals. I also know that spiders feed by drinking the bodily fluids of their prey. But these animals completely digest what they eat. If a human drinks blood, hemoglobin will be completely destroyed in the stomach. I am also thinking that if it is mammal blood, it may coagullate in the bowels, which I think may cause some harm.

I would like to have a reallistic way for my vampires to absorb the hemoglobin from the blood of others - their system will then either use this hemoglobin whole, or extract the heme from it to make new red blood cells. It doesn't have to be taken orally... With our current real world technology transfusions might do, but this is far from a low-profile approach and creates a dependency on blood banks/hospital centers that I would like to avoid. There would also be ABO/Rh factors to complicate things further if I went that way...

What I am looking for is something that allows for a higher degree of mobility and (at least social) stealth, and less dependency on 20th century technology. Either physiological adaptations, DIY methods (no matter how McGyver'ish, or how the victims would be handled etc.), or a combination of both.

How can I make this kind of "reallistic" vampirism viable?

  • $\begingroup$ how might such a creature have evolved, if you’re going for realism? That rules out any sort of tools or technology-based transfer methods. $\endgroup$ Jul 5, 2016 at 16:54
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    $\begingroup$ @Kelvin pheraps tools transformed what would otherwise be a death sentence into something you can live with? $\endgroup$ Jul 5, 2016 at 17:05
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    $\begingroup$ This would be a question of lifespan then. Your vampires in their natural state would be hemoglobin-independent until after they are of reproductive age. $\endgroup$ Jul 5, 2016 at 17:34
  • $\begingroup$ " I am also thinking that if it is mammal blood, it may coagullate in the bowels, which I think may cause some harm" humans drink animal blood in many cultures, it is perfectly safe. $\endgroup$
    – Keltari
    Jul 8, 2016 at 5:55

3 Answers 3


Just remove the stomach. Its main function is to transform what is eaten into a paste that can be digested, blood is already liquid so it doesn't need that. If the vampire's saliva contains an anticoagulant the blood won't clot either, though you may have to add some to the fangs as well to avoid coagulation before it even reaches the mouth.

Secondary functions of the stomach are to partly digest the eaten material, but that function could be emulated by a non-destructive stomach or transferred into the intestine.

Once in the intestine the blood would be digested and the hemoglobin absorbed (The blood may have to be broken down by enzymes which only vampires produce first).

Since another answer mentioned absorbing entire blood cells rather than just haemoglobin, doing so would be much more difficult.

Our current digestive system can only absorb single molecules, not entire cells, so that would have to change radically. Further, if entire cells are absorbed you have the same problems you have with blood transfusion; if the cells are not of the same blood type they will simply be destroyed by the immune system.

edit: everything I previously wrote is wrong!

The protein haemoglobin is too big to be absorbed by any digestive system similar to ours, further, I forgot that the vampire still needs to eat.

New answer: It is impossible to steal haemoglobin like that, unless you are also able to produce it from scratch.

Alternative: rather than being unable to produce haemoglobin vampires are unable to absorb iron as it is found in plants, instead they need to rely on absorbing it from the blood they drink.

In theory this approach still allows them to just eat meat. The only "easy" way I found to solve this is to make them profoundly repulsed by meat. This is a reasonable situation. It is not a problem for humanoids to have a vegetarian diet. This could also create interesting situations where someone claiming to be vegetarian could be an indicator of vampirism.

Additionally, vampires could be unable to digest meat. This would cause stomachache, diarrhea, nausea and vomiting upon assumption of meat.

Alpha-gal Allergy could also lead to allergic reactions when eating non-ape meat. Galactose-alpha-1,3-galactose is contained in all cells, including those in the blood, however, while meat is made out of cells, blood is made out of plasma (the liquid, not the state of matter) with cells floating in it. This means the quantities of C12H22O11 in blood are not significant enough to cause allergies. (Thanks to Renan for finding this, the medic I consulted didn't know about it)

Vampires of this form need to drink about 3dl of blood per day (on average), which is about as much blood as vampires drink in the book/movie series twilight (and many, but not all, others). This is assuming they have a somewhat more optimized system for assimilating iron than we do, which is reasonable if they need it to survive. Changing how optimized this system is also allows you to vary the required amount of blood, you should be able to change it to any value between 0.1 and 0.8 liters per day (on average) without going out of the bounds of realism.

Vampires still need to eat normal food, but they only need it for the calorie intake, they can supplement any missing nutrients through what they absorb from the blood (which contains almost all nutrients we need).

This allows you to keep the digestive system (almost) completely unchanged (which is optimal for social stealth, especially if you consider they might be subject to medical examination).

You still need to add anticoagulants to the fangs and saliva though.

Absorbing entire blood cells as proposed in another answer would be even more impossible (in fact, I asked a medic and it might really be completely impossible for an organism that has a biology based on that of mammals).

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    $\begingroup$ In that paragraph I asked for physiological adaptations (which you provided, +1), or some way the vampire could treat blood before ingesting/injecting it into himself. $\endgroup$ Jul 5, 2016 at 17:33
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    $\begingroup$ So what you meant to do there is specify how the previously described effect should be obtained? Not further changes that would make a vampire more mobile/stealthy? Are you also asking for an explanation of how such a vampire could evolve/why they can't produce haemoglobin? $\endgroup$
    – Annonymus
    Jul 5, 2016 at 17:36
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    $\begingroup$ Exactly. I am not looking to justify evolution right now, now how to further change their phisiology. I'd like to know what a vampire would need, right now, to incorporate foreign hemoglobin in their system in any way that does not require a common, clinical blood transfer. $\endgroup$ Jul 5, 2016 at 17:40
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    $\begingroup$ Ok. In that case my answer should be sufficient. $\endgroup$
    – Annonymus
    Jul 5, 2016 at 17:40
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    $\begingroup$ If they can still eat meat and get the required iron, then purely social factors discouraging this will not take root easily, unless there is a physical factor. This affects their survival, individually and collectively, and people do repulsive things to survive. One possibility might make food allergies or intolerance commonly linked to the disease - even mild ones affect preferences strongly, and if many different allergies occur in a population, then you get people avoiding the unsafe foods - and assuming people tend not to be allergic to other people, that blood would be very safe. $\endgroup$
    – Megha
    Jul 7, 2016 at 1:31

How about a venomous snake in reverse? Venomous snakes have a gland that produces venom and injects it into its victims through syringe-like fangs. Why not reverse the process where the gland sucks in the blood through the fangs and gets processed by the "vampire" gland. The gland can absorb the hemoglobin, and expel the plasma into the stomach, or out through the mouth.

  • $\begingroup$ Almost like a spider. ♫ Spider vamp, spider vamp, does whatever a spider vamp can... ♫ (have my upvote BTW) $\endgroup$ Jul 8, 2016 at 11:26

If what you want is a mean to the "vampire" absorbs the Red Blood Cells (RCBs) from his victim to then provide oxygen to his organs/tissue. What you need is an way to trow the oxygenated blood right into the blood stream of the vampire.

How the vampire does that can vary. He can produce a hypothetical type of enzyme in his stomach to protect the RCBs and absorb it by the walls of the stomach, into the bloodstream.

Just as a small note, I really don't know why such thing will evolve to this. You need to understand that, what you are changing here isn't the digestive system of the vampire, but part of his circulatory system. In this case, you can make it to be more like a disease. A virus that can reprogram the RCBs to enter his last stage of life in few hours, and not in few days, while changing the zone in brain that controls hunger to blood hunger and creating the hypothetical enzyme mentioned above.

RCBs and Iron-deficiency Anemia

Turns out that Iron-deficiency Anemia can be caused by the lack of RCBs in the bloodstream, or to a malformation in the RCBs (see: Sickle-cell disease).

Hemoglobin(Hb) and Porphyria

I must say that in the first time I didn't noticed the Porphyria, and because of that my first answer came out incomplete.

You see, Porphyria is a curious disease, despite the relation with the production of Heme, the disease itself isn't a cause to Anemia, or shortage in Hb, the small amounts of the porphyrins (the type of enzyme that precedes the Heme) are enough to produce Heme, and so Hb.

So, by that I return to my virus hypothesis. What if, the virus penetrates and attacks the infant RCB in the Bone Marrow, eating porphyrins enzymes, an by that triggering a most violent form of the Gunther disease. That will also cause an reaction that also trigger a form of Iron-deficiency, since the hemoglobin production will be compromised, and you will still have the symptoms of the Porphyria.

Blood Type Problem

The blood type is defined by the existence of two groups of Antigens in the Blood, the ABO group and the Rh group. The presence or not presence of this Antigens, defines who can donate and receive from who.

So if you are A+ you are positive for the B-Antibody in your plasma and positive for the Rh-Antigen Group.

I think the most elegant answer to this problem is the virus can also make the the blood type of the infected change, in a similar way of what happens with an patient that received an bone marrow transplant.


I've insisted in the theory of the RBCs absorption because to me appears to be the most plausible way to do what you want, try to create a realistic way to absorb the Hb from the victim. Dissolving the RCBs to extract the Hb and after recombining into the RCBs probably will demand a creation of a whole new organ, since no organ does anything like that. The own RCBs is destroyed by WCBs in the blood after a time.

Anyway, I want to thanks the OP for making me interested in cellular-biology. Hope the improved answer helps.

  • $\begingroup$ Absorbing red blood cells is way more difficult than absorbing haemoglobin, and the questioner never asked for it. $\endgroup$
    – Annonymus
    Jul 5, 2016 at 17:33
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    $\begingroup$ @Kelvin mammals RCBs don't have DNA, the are anucleate. $\endgroup$ Jul 5, 2016 at 17:42
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    $\begingroup$ @Renan the problem with only absorbing the hemoglobin is that in the human body lack a way to absorb it into the RCBs, the are produced in the maturation process of the RBCs and lasts until the the cell is destroyed by a White Blood Cell. $\endgroup$ Jul 5, 2016 at 17:48
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    $\begingroup$ at any rate you still need to deal with incompatible proteins, etc. Most humans cannot even donate blood safely to one another; hence blood types $\endgroup$ Jul 5, 2016 at 17:51
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    $\begingroup$ How would the vampire know the blood type? As they say, everything is edible, it’s just a question of how many times. Some things, like poisonous mushrooms, are only edible once. $\endgroup$ Jul 5, 2016 at 17:57

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