Hematology/human blood (vampire story)

Physician here...a few thoughts in no particular order.

1. venoms are injected, poisons are absorbed (skin, respiratory system, GI system...)
2. If you are sticking with real human physiology, any blood that a person drinks is broken down like all other food. The iron could be important but uh...there are easier ways to get it. If your humans that need to drink blood are going to actually drink it, you will need to add some other modification of their body systems to address this.
3. The time a substance stays in your body is infinitely variable, depending on clearance mechanism, concentration, and factors specific to the individual. You could go any where with this and it would be believable.
4. There is no such thing as cloned blood in this world, there are some things only the human body can do and we can't replicate it in a test tube. While sci-fi does allow for amazing leaps of technology, I think it is still being loyal to the genre to say "nothing beats home(human) made" However, I'm not sure why your vampire humans couldn't just receive transfused whole blood. Maybe they LIKE biting people?
5. It would be easy to explain why a person couldn't generate their own blood (blood cells are made from hemopoietic cells in our bone marrow) but harder to explain why these individuals have to DRINK it. It is doable, you are just going to have to work some more physiologic changes into your vampire species.

Hope this helps

Dr. Suzanne

Not that this goes to your questions, but if you're trying to keep it scientific, something that never gets considered in vampire stories* is the copious urine produced by blood-feeders.

Also gut bacteria are important.

*Or maybe it does. I haven't read many.

Along the lines of the esophagus or tongue absorbing it, if they're a separate subspecies of human, maybe along the way they've developed a sort of 'gizzard' a pouch that holds the blood, and adds special enzymes to absorb or digest it. As to biting, it might not be necessary, but maybe it's cultural. They evolved into blood-suckers, and no true vampire would use a processed, chemical substitute.

Venom it is. Although is it still called a "venom" if it isn't actually dangerous? The vampire stuff is essentially a sedative

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Sure, call it venom. Like everything in a Sci-Fi/Fantasy world, things are what you define them to be.

So, from days to weeks?

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Yes, kind of like marijuana.

Maybe their oesophagus and/or tongue absorbs it before it reaches the stomach?

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Those are good ideas, also frimble3 has some good ideas

Also, just a thought, the part of the anatomy that stores the blood shouldn't be simply a pouch, or bladder. It should have ridges or frills inside, to provide more surface area for processing, and, to reduce the amount of blood taken in, so that victims aren't just sucked dry at one go. (Unless that's what you want.) Maybe they evolved from smaller creatures that lived on rodent or small mammal blood, and the blood isn't their sole source of food, it just provides something that their normal (vegetable?) diet doesn't provide?

I don't think people would like my vampire novel if I wrote one. My vampire would be squeamish about blood, terrified of biting people, and would do anything to mask the color and taste. And he would always have a cardboard silhouette handy if he has to walk past a mirror.

efreysson said:

The idea is that they just feed a little at a time.

And on that topic, if I assume they just take a couple of gulps in each feeding, if they do this every day to the same person, how long before the victim starts to feel the loss?

And this goes for the vampires too. If their bone marrow doesn't produce enough blood, what is slow blood loss like? What are the symptoms and how do they progress?

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A good starting place for you would be UK practice on blood donation. I used to give blood a pint at a time and you were limited in the number of donations you can give in a year - I've forgotten the numbers. As I understand it, a healthy human body has sufficient reserves to replace a pint of blood quickly, but not a second pint - and then there is a lead time to build up your reserves again. Before giving blood your weight and height were checked - to make sure that you were big enough that a pint of blood was not too high a percentage of your total blood. Also checked for anaemia - that you had sufficient iron in your system. If too much blood is taken, anaemia would be one of the problems - and that means you could look a bit pale and that being short of haemoglobin you'd be a bit short on oxygen transport around your body - so might get dizzy if you move too fast, get breathless sooner when you run. More than that you'll need a more medical source than I am.
I'd also be concerned regarding the strain on major organs, especially the liver, as that is also involved in blood production. Being chronically short of oxygen can cause problems all over, including lungs and heart muscle.

Al X. said:

And he would always have a cardboard silhouette handy if he has to walk past a mirror.

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"That just raises even more questions!"

If you want an interesting symbiosis, your vampires could feed off people with certain types of Porphyria. It's a genetic disease where the body produces too much of a certain blood component. The treatment for severe cases, believe it or not, is bloodletting.

There's different types of Porphyria. Some cause severe photosensitivity, so that would be something they'd have in common with vampires. (If I go in full sunlight, my skin immediately starts to hurt. A few minutes and I'll develop tiny blisters. Longer, I get hives and nausea.) You can learn more at the American Porphyria Foundation.

I got around this issue by realigning the focus from the blood itself to the life's energy it carried, and different methods of acquisition. I don't want to hijack the thread, so you can PM me for further details.