We used to have blood drives at work every 8 weeks. At one donation appointment, they wouldn’t let me donate because I was one day shy of the 8 week waiting period. They told me to come back the next day and I could donate.
Unfortunately, I did not have an appointment scheduled for the next day, and the wait for walk-ins was about two hours, so they did not get any blood from me that visit.
As I understand it, that initial shock is mostly just from the loss of fluid volume, and that you could fix it by immediately replacing the blood with an equal volume of saline IV.
Blood donor centers just don’t usually do that because, under ordinary circumstances, you can also just make sure to drink plenty of water for a couple of days.
It takes 6 weeks to grow a new blood cell from start to finish, unless one has hemochromatosis. Most people don’t, so they may get away with donating blood every two weeks for a while, but it’ll eventually catch up to them. After a while, almost all their RBCs will be immature and not able to transport oxygen very efficiently.
You get a new pint of blood every 14 days. If you give one pint every 14 days, you’re loosing 1.9 pints (including ageing) and gaining only 1. But you get increased supply rates if your levels are low, so while your bank is ramping down, your supply is ramping up. But your supply rate is also limited by things like your iron supply, which is /not/ automatically ramping up. So you can do this for a while, but not forever.
After 2 months you’re down 4 pints. But now your production is ramping up, and simplisticly, your blood donation only has half as many red blood cells (the rest is just water), and a higher proportion of those donated are imature cells anyway: you aren’t loosing a pint of active RBC anymore. The weaker you get, the more RBC are produced, and the fewer are donated.
It’s a bit more restrictive than that. If you’ve ever received a blood product as part of a medical procedure since 1980 - or even if you think you might have - then you can’t donate. I know I have, so I haven’t been able to donate for nearly twenty years now.
The UK blood transfusion service goes with cups of tea and some biscuits (cookies).
Oh, sure, blood services here give you drinks and light snacks afterwards, too (though around here, it’s usually juice rather than tea). But you’re not likely to completely replenish your fluids in just 15 minutes in the canteen.
(also note, of course, that both tea and juice can be regarded as slightly impure water)
A reasonable rule of thumb is that a red blood cell lives in the circulation for about 100 days. So, you lose about 1% of your RBCs every day and when things are in equilibrium you produce an offsetting 1%.
Normally, a person has around 1/10 to 1/15 of their RBCs removed when donating one unit of blood. They will replace this amount of RBCs in about 7 to 10 days.
The production rate can be ramped up by at least several-fold if the rate of destruction/removal/senescence increases but only so long as the supply of essential ‘building blocks’ of RBCs (and the hemoglobin they contain) such as iron, vitamin B12, and folate is maintained.
I am unaware of any data that suggests you can ‘tire out’ your bone marrow to the point of not producing sufficient RBCs (and hemoglobin) as a result of it working too hard. If the supply of the essential precursors is uninterrupted, the bone marrow will keep pumping things out. So if frequent blood donation ever leads someone to become anemic, it’s because they’ve not made up for the lost iron or are leaking blood from somewhere in their body (or have become deficient in folate/B12).
My boss (in my first job) told me that where he came from (Norway??) they gave him a glass of beer with each donation.
My blood bank asks (among a LOT of other questions) if I was in certain parts of Europe in the 80s. Not sure why. They also ask about having cancer and receiving blood, but if it is long enough ago the screener is okay with it.
I wonder if the woman mentioned in the earlier post, who allegedly became permanently anemic after donating during WWII, had pernicious anemia, which even today can be hard to diagnose, but is relatively easy to treat.
Cruetzfeld-Jakob disease (mad cow) maybe?
The questions about Europe are primarily regarding mad-cow disease. My wife spent a year in England in college ('98) and the Red Cross won’t let her donate at all as a result. Prions aren’t anything to mess with.