How fast is blood replaced?

[Eternal_Freedom]

How quickly is blood replenished in the average adult male body?

I ask becaus I donated blood at midday Friday (they take a pint IIRC) and I was wondering how long until I'm "back to normal."

[Dave]

If memory serves the soonest you are allowed to donate again is 8 weeks, which should give you a conservative upper limit.

[SCRawl]

Your volume should be back to normal within hours, so drink lots of (non-boozy) stuff so that volume has somewhere to come from. What will take a little time is replacing the red blood cells -- that's going to take a month or more. And yes, in Canada at least the time between whole blood donations is eight weeks minimum.

Funny story. When in university I donated blood, then saw my bus and sprinted to catch it. I almost lost consciousness (though I did make the bus), and I honestly was wondering if my last thoughts would have been something like "now that was stupid".

[Eternal_Freedom]

Awesome. Thanks.

[Gil Hamilton]

Different components regenerate at different rates after giving a unit of blood.

-Plasma is within a few hours if you drink plenty of water (drink plenty of water, before and afterwards).
-White blood cells will probably be back in about a day. Platelets and some proteins take a few days.
-Red blood cells require four to six weeks. Making that much hemoglobin requires alot of effort by the body, and while the body automatically starts replacing the red blood cells, they just take a while. Keep in mind that a unit of blood doesn't take enough blood cells to really hurt you, though you might fatigue slightly faster for a few days after giving blood.

If you eat lots of dark, leafy veggies like spinach or broccoli, it will help the body regenerate RBC faster, but really, you shouldn't stress over the loss. The most important thing is drinking extra juice or water after you donate to help get the volume back and you'll be fine.

[Eternal_Freedom]

I wasn't stressing as much, but the nurse said "be careful next time you're in the pub." Since it's at a university, obviously all students spend all the time in the pub. I was curious as to how long it takes.

Amusingly, I was in the pub within an hour, but only drinking Coke

[SCRawl]

I've heard of people donating blood and then going directly to the pub, in hopes of getting drunk cheaply. This strikes me as incredibly dangerous, because the last thing you need when you're low on fluids is to be drinking booze.

[Sea Skimmer]

I had internal bleeding which drained out a quarter of my blood supply and it took a week to have any measurable rise in the red blood cell count before which they would not allow me to leave the hospital which was most annoying since I had been on a four day trip to Texas. The US Red Cross says 4-6 weeks to replenish red blood cells, 8 weeks between donation. As I recall they had me taking iron pills for about that long until the cell count stabilized.

[SCRawl]

That's 4-6 weeks to replenish the red blood cells lost from roughly 1/15 of an average person's blood supply. You lost about four times that amount, so yeah, you had a longer recovery time. Bone marrow can only work so fast...

[Sea Skimmer]

I thought they took a pint when you donate blood? I've never done it myself since for separate reasons it was recommended I never do so; blood pressure does not regulate well. Kind of annoying since I'd like to do so and doesn't sound like it would kill me, but it'd lead to me fainting and scaring all the red cross people.

[SCRawl]

You would probably be screened out anyway, if you have blood pressure issues.

I was told by the blood people that a standard donation was about 1/15 of one's blood supply, but some googling tells me that a standard unit of blood is about 450 mL, and since a 70kg person has about 5-5.6L of blood that means the amount is more like 1/12 to 1/11 of the total amount. Still, if you lost 1/4 of your blood that's three times a normal blood donation, which strikes me as pretty significant.

[Sea Skimmer]

I'd imagine I would be if I told them, so I've never attempted donation. At least my blood is nothing specifically valuable like O negative. I always thought the average person was about eight pints of blood, and a donation was one pint. I guess then that isn't true; kind of makes the stomach sink to now realize I was worse off then I thought. The doctors at the time were not very forthcoming with details like that since I was a minor. I know know it was two pints because I read it on my medical records later. I have to say though, once the pain of just breathing went away, it was just kind of interesting how a person can be so massively weakened and yet have not a single mark on your skin. Cause BTW, this was like nine years ago but was recounted on SDN so no secret, was a lacerated spleen from being knocked over onto a railing.

[Eternal_Freedom]

I've heard of people donating blood and then going directly to the pub, in hopes of getting drunk cheaply. This strikes me as incredibly dangerous, because the last thing you need when you're low on fluids is to be drinking booze.

Yeah, it's dumb. I've seen plenty of students here doing the same thing. Luckily no one has come across a serious problem yet.

[PainRack]

You guys have that fancy machine that measures how much hb you have, as opposed to the "you have enough iron to donate" solution test thingy?

[Eternal_Freedom]

Not here, they take a dorp of blood and drop it in some chemical. Sweet and easy.

Well, 4 days later and I'm feeling exactly as I was before, even after a drink or two. Woo. Thanks for the answers everyone, they've been most helpful.

[Simon_Jester]

You would probably be screened out anyway, if you have blood pressure issues.

I was told by the blood people that a standard donation was about 1/15 of one's blood supply, but some googling tells me that a standard unit of blood is about 450 mL, and since a 70kg person has about 5-5.6L of blood that means the amount is more like 1/12 to 1/11 of the total amount. Still, if you lost 1/4 of your blood that's three times a normal blood donation, which strikes me as pretty significant.

Well, one pint *is* about 450 mL, so that part of the calculation is right on Skimmer's end. On the other hand, he may have been a pretty scrawny kid when this happened, so he may have had less than the usual 9-10 pints.


This is highly unscientific, but:

Red blood cells are there to carry oxygen, right? So theoretically, a lack of X% of your blood cells should be sort of like a lack of X% of your oxygen supply. Now, donating 450 mL of blood is like losing about 8-9% of your red cells. What altitude corresponds to a 10% decrease in your oxygen supply?

So I looked here:
http://www.engineeringtoolbox.com/stand ... d_604.html

So in terms of your ability to extract oxygen from the air, giving one unit of blood is like moving quickly from sea level to a few thousand feet. You probably won't actually notice this unless you try to do something strenuous for which your body demands 100% of its capacity... and finds that it only has about 90% of its capacity. You'd acclimatize quickly, too- which might be why you don't feel persistently weakened by a single blood donation.

Me, I give double red donations on an apheresis machine, because it means the Red Cross only bothers me once every four months instead of once every two months. I'm a big guy, so I probably contain more blood than average, but we can cautiously estimate that I'm losing something like 15% of my red blood cells. I am likely to feel somewhat weakened for a day or so after a donation, although I don't get particularly dizzy or have fainting spells.

That reduction in red cell counts would correspond to an altitude change of, oh... 5000 feet or so. Like flying to Denver- still something you can do without being badly messed up, and something you can adapt to quickly.


Skimmer had lost more like 25% of his red cells. That corresponds to suddenly going up to an altitude of... I don't know, more like ten thousand feet? Which is enough that if it happened quickly, you would be very seriously weakened, you might even pass out. I remember one time on vacation I went up relatively quickly to 12300 feet and it was... right about at my stall ceiling, if you will. I was able to walk and talk and think, but anything much more strenuous than that and I would have collapsed. And there are people who never do adapt well to altitudes that high or a little higher, so you can see how a loss like that would weaken you until the blood got replaced- I'm guessing your body can't adapt to getting much less than 70-80% of its normal allotment of oxygen.

Does that make sense?

[Skywalker_T-65]

I'm hardly a scientist, but I have donated blood before. And for me, that's what I feel like when I do so. I already have lung problems though, so that coupled with less blood/oxygen supply means I can't do much of anything even with just a single donation. Which wasn't fun last weekend when I donated blood and had to mow my lawn the very next day. Really not fun.

But hey, my blood type is A+ so I don't have the Red Cross bugging me about donating as often as possible.

EDIT: Of course that was slightly off topic. Back OT, whenever I donate blood I recover fairly quickly. Aside from the aforementioned example, I can normally be back to normal in 3-4 days. It certainly does help to drink a lot of water though, and I can say that from experience. And drinking alcohol of any variety...okay, I'm 18 so I haven't done that, but it still sounds stupid. That thins your blood right? If you drink too much anyway, which would mean that you are thinning your already diminished blood supply. Hardly sounds like a good idea.

[Sriad]

Looking at some study abstracts (the relevant search is along the lines: blood donation VO2 count) max vO2 during strenuous exercise in the 24 hours after donation drops ranging from 10-20%, with variable levels of impact on heart rate observed. In terms of atmospheric pressure that corresponds well with going from sea level to about 5280 feet. It feels better than an elevation change because you're still delivering oxygen to your blood as fast as before, but the oxygen isn't delivered to your tissues so well.

[Bedlam]

Not all of your blood is in circulation at any one time, the Spleen and Liver (I think) store about a pint of blood at any one time and thus you have a back up in the case of blood loss so that you dont immediately suffer from a reduction in oxygen carrying capacity. So donating a pint of blood doesn't normally reduce your oxygen supply significantly.

[Sea Skimmer]

Yeah organs have a lot of blood in them, and all the veins and arteries can slightly constrict to help maintain pressure. The extreme form of this is going into shock.

[Dave]

I've heard of people donating blood and then going directly to the pub, in hopes of getting drunk cheaply. This strikes me as incredibly dangerous, because the last thing you need when you're low on fluids is to be drinking booze.

That was definitely the running joke in my fraternity. Surely some people I know attempted it, though I don't recall if there was an actual impact on intoxication rates.

You guys have that fancy machine that measures how much hb you have, as opposed to the "you have enough iron to donate" solution test thingy?

I've never seen anything but a machine. Drop of blood in a specialized pipette (presumably with pre-measured chemicals in it), slam it in the machine and you get numbers in ~15 seconds.

When I get regular blood tests done (health insurance for work), they take a single pipette (presumably without chemicals) and put it in a machine. It spits out total cholesterol, HDL, LDL, triglycerides and A1C (long term blood glucose, tests for diabetes) in 2 minutes or so.

This is highly unscientific, but:
[snip]
Does that make sense?

I love the back of the envelope calculation. Excellent way of putting it in perspective.

[SCRawl]

The alternative to the machine is a solution of copper (2) sulphate in a cylinder. Put a drop of blood in the cylinder, measure how much time it takes to get to the bottom. If it's fast enough, and therefore dense enough, then you pass. If it isn't, you're deferred. Canadian Blood Services (the entity that collects blood for transfusions here) has been using the machine at my local clinic for close to a year now.

[cosmicalstorm]

I rode my bike around town for three hours after my last donation. That gave me two days of heavy fever complete with hour long fever-dreams where I lived as a street child named Pepe in Mexico. It was a surreal experience that made me respect my immune-system. Currently my iron-levels have been falling steadily since five years back, the next time I go there they will measure my levels before allowing me to donate. I will temporarily eat iron pills to bypass this issue. Personally, I prefer low iron levels, it may be bogus but I've heard it said more than once that the body is less sensitive to various bacterial infections if the iron levels are generally low.

[PainRack]

Yeah organs have a lot of blood in them, and all the veins and arteries can slightly constrict to help maintain pressure. The extreme form of this is going into shock.

http://emedicine.medscape.com/article/1 ... view#a0104

The main response is that your body compensate by constricting its blood vessels peripherally so that your cardiac output is compensated for(squeezing out blood) and your heart beats faster in response to tissue hypoxia. There's also peripheral vasodilation if the issue is more hypoxia than hypovolemia and this can leads to giddiness and fainting, especially if you suddenly sit up or after strenous activity.(orthostatic hypotension,aggravated as your BP is already lowered due to lower peripheral resistance.)


How effectively your body handles this is individualistic. The stricture against doing strenous activity doesn't affect me at all. I once hit the gym a few hours after donation, having drunk enough water to replenish my fluids.... although that was dumb in retrospect.

[Kreller1]

Second time I donated, after I got home from work, I attempted to move a large box and nearly hit my head on it when I fainted. Now I use that as an excuse to not have to do *anything* physical on the days I donate.