How much blood can one donate?

Is this for medical reasons (i.e. they have an upcoming surgery and need to bank blood ahead of time), or to donate to other people?

At least in the US, you have to be 18 to donate.

wendymarlowe said:

Is this for medical reasons (i.e. they have an upcoming surgery and need to bank blood ahead of time), or to donate to other people?

At least in the US, you have to be 18 to donate.

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Nope- you can be 16 with parental consent. you can donate blood every 56 days- they take 1 unit when you do which is roughly around 1 pint.

I got this from the Red Cross website:

You must wait at least eight weeks (56 days) between donations of whole blood and 16 weeks (112 days) between double red cell donations. Regulations are different for those giving blood for themselves (autologous donors).

It is also dependent on body weight. A 5 feet 2 inches adult friend of mine gave blood - and it was allowed because she was just over the minimum weight. Don't know what that is.
She fainted when she got up.

What hadn't been calculated was that she was overweight for her height, so the proportion of blood taken was a bit high.

Bolero said:

It is also dependent on body weight. A 5 feet 2 inches adult friend of mine gave blood - and it was allowed because she was just over the minimum weight. Don't know what that is.
She fainted when she got up.

What hadn't been calculated was that she was overweight for her height, so the proportion of blood taken was a bit high.

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for the USA for the American Red Cross ( this differs slightly from state to state) you need to be at least 5'1" and weight at least 110lbs.

it does not matter if you are over weight for your height- that is not what made her faint- your body must produce enough blood via capillaries to supply your whole body with blood- extra fat and all- so she had the blood to spare- her blood sugar was either low- or she sat up too fast - or she had a vago-vasil response to giving blood-meaning she was squeamish and well, fainted or a host of other reason for why she fainted after giving blood- but being overweight for her height was not one of them. (Shea- who has worked on many a red cross blood drive)

Interesting. Thanks.

IIRC the average human adult body has about 8-10 pints of blood. This would vary based on weight and height. For a teenager, I'd assume they are not at their full height/weight yet, so it's probably more like 6-8 pints total.

Since it takes 8 weeks for the body to regenerate that lost pint of blood, if your teenager donates a pint every month, I would bet that he would be at high risk for anemia.

In a DIRE situation, I would guess that he could donate maybe 2 pints of blood, monthly, for 2-3 months max. At 2 pints I would bet he would feel the effects (dizziness, low blood sugar) even after the first donation, and after the 2nd or 3rd he is really going to be struggling. I cannot imagine an ethical medical professional taking that much blood, that often, outside of a really catastrophic situation.

If the OP could provide a few more details, perhaps we can help get this figured out...

I've donated blood 8 or 9 times, and they only took about 1 litre of blood. I have to wait 3 months before doing it again.

If you're donating whole blood then as mentioned above, you can only donate every 12 weeks. There are other options though:
You can donate around 800mL of plasma every 2 weeks. It's a much more involved process and not everyone can do it - you need wide veins.
Platelets are every 2-4 weeks. I don't know anything about this process but I'm sure you can google it.

Make sure you plan a method for the hole to disappear in the text. The blood has to leave the body somehow and unless she's a drug user, someone is going to notice the recurring holes in her.

SKara said:

From your replies, I was wondering maybe my protagonist (16 years old) could donate a pint of blood every two months. In that case, she wouldn't be aware of it, right? She wouldn't know that someone is secretly doing it to her?

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They'd have to be very skilled at taken blood, possibly with some supernatural aide if that fits your story. Even if the blood is taken from somewhere out of sight (back of thigh, maybe? Are there easy veins there? They'd have to vary up the spot they use as well...) there'd be a risk of vein collapse & bruising which would draw the MC's attention to the spot.

She'd also need to be having a balance diet with a lot of iron in it. If she's unaware that she's losing blood and is very active, a vegetarian, or just a light eater, she could easily dip into anemia.

If possible, I'd mention that the MC's mum is a regular donor (maybe MC needed a transfusion to survive when she was born and her mum's been a regular donor ever since to "pay it forward") which would hint that your MC has good veins for donating.

SKara, if you haven't donated blood before you could donate at a local blood drive for research.

SKara said:

Thanks. Maybe I could use the holes to hint to her that she has some memory gaps, because finally she has to realize the secret happenings somehow and try to find out the person.

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If she has recurring memory lapses along with the holes and/or bruising, it would be absolutely plausible for her to wonder if she IS being drugged. I could see her asking a friend or group of friends to keep watch to see if she's sleepwalking or if someone is breaking into her home. It also gives a place for dialogue, so it's not just her musing to herself in the text about the weirdnesses. Secondary characters ROCK as a method to amp up the fear or mystery.

If you want to explain away the bruises:
When I was in college, I lived in an apartment in a really old house (100+ years). That apartment had a lot of hard edges and protruding cabinets and shelves, plus it was pretty cramped and crowded. Now admittedly, I'm not a very coordinated person. I've never bruised easily, but I would regurlarly find bruises without any memory of hurting myself.

SKara said:

I hope the bruising won't appear until the third or fourth time?

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It really depends on your donor. Maryn's an experienced donor, so if your MC is a good donor candidate I'd use her advice as a basis for your MC.

I bruise almost every time I donate, though, and if a vein collapses then I bruise very badly. But genetics have given me very thin veins and mysterious other factors give me very low iron, so I'm a worst case scenario.

Quite a few nurses have failed to get any tangible amount of blood out of me. (I'M A STOOOOONE!) Last time I tried to donate the nurse said my right arm had no blood and was "full of air", so I'm currently registered as left-arm only donor.

SKara said:

EMaree, if you don't mind, can I ask why you keep donating blood if you already have iron deficiency? Just curious.

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A very sensible question to ask! We're very short on donors around here, so as long as the nurses are comfortable taking blood from me I'm up for trying. I'm not particularly scared of needles or squeamish about blood so I'd feel awful if I didn't attempt to donate.

I warn them in advance that I'm problematic, they run checks on my iron levels, and the nurses and doctors have been very clear that they'd prefer I try rather than give up.

It's a bit of a trial-and-error process, and it took a long time, a few nurses and a variety of donation centres to discover why these issues were happening. I think it was on my fourth donating attempt that a nurse confirmed my right arm was unusable, and on my next visit they're going to check if they can actually get a full pint out of my left. We've also been going through different spots each time (back of both hands, inside of both elbows, with and without blood pressure cuffs etc). There's still hope we'll crack a way to get blood outta me!

Maryn said:

I have "bad veins" but when I warn the nurse, they do what they can to get me in one stick. I require extra monitoring to keep the flow going, too, often moving the needle an eensie bit when it's in place.

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Oh man, moving the needle feels weird! Not sore, just weird.

They kept a blood pressure cuff on at max setting last time I went (it was just a sample to test, not a full donation). I have to admit, that was a bit scary to go through. Again, not sore, but the feeling of slowly losing my arm freaked me out. I'm hoping to avoid that next time...

But most of the people around me at the blood drive donate easily, the physical donation taking 15 minutes or less and completely pain-free other than the single poke. Body builders, whose veins have enlarged to supply blood to larger muscle mass, are apparently extremely fast donors.

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I wonder if that'll work for me? *runs down to the gym*

(Okay, replace 'runs to the gym' with 'takes the dog on a slow walk')

EMaree said:

They'd have to be very skilled at taken blood, possibly with some supernatural aide if that fits your story. Even if the blood is taken from somewhere out of sight (back of thigh, maybe? Are there easy veins there? They'd have to vary up the spot they use as well...) there'd be a risk of vein collapse & bruising which would draw the MC's attention to the spot.

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EMaree said:

It really depends on your donor. Maryn's an experienced donor, so if your MC is a good donor candidate I'd use her advice as a basis for your MC.

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Although the donor's veins and other factors can affect this, it actually depends on the skill of the phlebotomist (a fancy name for the person doing the collection) more than the donor. We have some people who are very skilled and can draw even problematic donors with no bruising.

Regarding the young lady who fainted, thanks Shea for identifying the real possible causes for this. And I hope someone lets the young lady involved know. Some of the causes can easily be managed so it doesn't happen again should she donate in the future.

Back to the original question about frequency - it has been correctly identified as every 8 weeks for whole blood (at least in the US), which is probably what the person getting the blood from her without her remembering would be drawing. It is easier, quicker and takes less equipment. A "double red" takes longer and a special machine (as do plasma and platelets) called an aperesis machine. The frequency is set for the protection of donor and their health. Of course, that presumes your blood stealer gives a rip about that. If the MC is being coerced into doing this, the person doing it probably doesn't care about the regulations.

PK - who actually works in a Blood Bank