Insert obligatory vampire joke

February 27, 2010 5:00 PM

What happens after you donate blood?

What happens several hours to weeks after you've donated, in a physiological sense? (Like, does there exist a timeline of the body's responses to lost blood/donation?) Does your body replace the lost blood with fluid until it can recreate lost blood cells? How long does this take? How long until your blood is back to "normal"?

Also, I have a really rare blood type, AB negative. Is my blood "better" for someone with the same blood type than say, O negative? I guess I'm hoping that it's worth it for me to come in despite the low number of people who have my blood type.

posted by pyrom to health & fitness (13 answers total)

Your body is always replensihing your blood supply. That's what the marrow in your bones does.
posted by dfriedman at 5:05 PM on February 27, 2010

Erythropoietin is released from the kidneys, we think due to cells measuring blood oxygenation levels. This stimulates your bone marrow to make more RBCs. Also, as the body's water and sodium levels re-equilibrate in the different body compartments, your kidneys will hold onto more sodium (aldosterone) and more water (anti-diuretic hormone), and your fluid volume is probably back to normal within a day (assuming you're eating and drinking afterward).

Most estimates suggest that your amount of RBCs (hematocrit) is back to normal within a few weeks; you can donate every 56 days of a whole blood unit (more frequently if you're just giving platelets, less frequently if you're giving more RBCs).

You're AB, so you're a "universal receiver." You can get any Rh negative blood type; O is the "universal donor," because anyone can receive their blood (and this is the blood type we use in trauma settings, when we don't know someone's blood type but need to emergently give them blood products).
posted by gramcracker at 5:16 PM on February 27, 2010 [3 favorites]

No, your blood isn't "better" for an type AB person. O is just as good. If an type-AB person needs a transfusion, they'll probably use type-AB blood if they have it, because it's no good for anyone of another type, so they may as well use it up.

It's still great that you're donating, though - thanks! :)
posted by Salvor Hardin at 5:41 PM on February 27, 2010

Gramcracker did a great job of summarizing the physiologic responses; yes, your body holds onto more fluid in the short term (hours to days) while your bone marrow ramps up its production of more red blood cells (hours to weeks).

There's some simple math to demonstrate a very simplified time to repletion of the blood you donate. Your body has 10-12 pints of blood; let's make it 10 for easy math. The typical RBC donation is 1 pint, or 10% of your total blood volume. The average lifespan of a red blood cell is 120 days from the time of production to the time of destruction, so on average, when you are otherwise normal and not surrendering 10% of your blood volume to a blood bank, your bone marrow chugs along producing 1/120th of your total blood volume (0.08 pints) every single day. At this rate of production, it would only take just over 12 days to make 1 pint of blood. Of course, in the case of donating, this is highly simplified -- you have to replace the RBCs you donated AND the RBCs that're naturally being destroyed, so it would take a little longer, but your bone marrow also significantly ramps up its production rate, so the time is cut down a bit. Overall, it's rare if someone isn't back to their normal lab values within 2-3 weeks, and it's even more rare if they're not back to normal performance levels in 2-3 days.

As for your AB negative blood, it's always better for a donor to receive their exact blood type -- so yes, it's definitely worth it for you to donate.
posted by delfuego at 5:43 PM on February 27, 2010 [1 favorite]

I don't properly understand the details myself (have studied biology at university level, spent a lot of the blood-related bits concentrating very hard on entirely non blood-related things), but do know that your rhesus-negative blood can be safely donated to rhesus positive people - this means that your blood can be given to about another 5% of the world's population, the AB Positive people, as well as the 0.5% or so who are AB Neg. That's a lot of people who could use your blood!

As I understand it, yes, it's always helpful to get blood of all types. They don't just match on the really obvious bits (A/B/O, Rh +/-), but when they have time - for scheduled surgery - they'll do a match of thirty or so different factors, so having a wider range of detailed blood types available is good.

Thirdly, because blood type is inherited, different types are more common in different ethnic groups. If that's something that's important to you, the person you help might be more likely to be a member of your ethnic group.
posted by Lebannen at 5:47 PM on February 27, 2010

I have a really rare blood type, AB negative. Is my blood "better" for someone with the same blood type than say, O negative?

I have AB positive blood. I grew up in a small town with a mom who was also AB+ and she would [rarely] get a phone call from the hospital when someone came in needing her particular blood type, to come in and donate. So yes there's a value in you giving [and, relatedly, my blood type made me eligible to donate for money in a cancer study in Seattle for several years].

I can't speak to the physiological stuff except that, as a frequent donor, I feel fatigued and thirsty for a few days [and if I have a beer, I get tipsy more quickly] and then basically don't notice it once the injection site has healed over a few days later.
posted by jessamyn at 5:48 PM on February 27, 2010

Oh, and I should say that for donating red blood cells, O-negative is the "universal donor", but for donating any other blood products -- plasma, platelets -- YOU are the universal donor. So if you want real motivation to go donate, there's a real need for blood products other than RBCs from people who are AB; the donation process is a bit more involved than just donating RBCs, but it's a real need.
posted by delfuego at 5:48 PM on February 27, 2010

gramcracker: "You're AB, so you're a "universal receiver." You can get any Rh negative blood type; O is the "universal donor," because anyone can receive their blood (and this is the blood type we use in trauma settings, when we don't know someone's blood type but need to emergently give them blood products)."

I thought universal recipient only referred to AB+ because you can't give any Rh positive blood to an AB-, and universal donor referred only to O- because they don't have any Rh factor to worry about.
posted by IndigoRain at 8:52 PM on February 27, 2010 [2 favorites]

There are actually about 30 blood type systems of which the ABO and Rhesus +/- are the two most important. Look up cross matching for details of the other systems.
posted by atrazine at 10:23 PM on February 27, 2010

Like delfuego said, it's important to remember that RBCs are relatively short lived and are constantly being replenished regardless of donation. The broken down components of dead RBCs are what make your poop brown -- otherwise it would be closer to vomit in color. So the marrow is quite the little factory and is always cranking them out, so donation just means that it has to work a little harder for a couple days.
posted by Rhomboid at 4:35 AM on February 28, 2010

If you have the time, you should really consider giving platelets instead. I'm AB- as well, and the ABs are the universal platelet/plasma donors. There are a *lot* fewer of us, as you know, than Os, and so our platelets are valuable. I give platelets every two weeks, and the process is pretty smooth. It takes about two hours, and all the donation centers I've ever been to have little personal TV/DVD players, and a library of movies to keep you entertained while they suck out your plasma and platelets and give you your RBCs back.

I'm surprised that no one at donation centers has talked to you about platelet donation before -- I started giving blood ten years ago after college and at my first donation they asked if I would be willing to do platelets instead. It takes 6-10 units of whole blood to make one unit of platelets, and as a regular platelet donor, I average 2.5 units of platelets per donation. That means that my two hours on a Saturday morning is equivalent to donating 18-30 units of whole blood.

And I can do this every two weeks with no ill effects at all.

So think about it -- ABs can save a lot of lives. :)
posted by Concolora at 2:08 PM on February 28, 2010

Yay, platelets!

I gave blood at the Brigham & WOmen's blood bank in Boston...until I saw the t-shirt they gave to platelet donors: MUCH cooler. So I gave platelets every two weeks for a couple of years. Then they changed the rules for donors and my over-six-months of time abroad ruled me out as a risky donor. *sigh* I miss donating, and I never had a negative or lasting reaction.
posted by wenestvedt at 7:59 AM on March 1, 2010

Seconding (etc) platelets. Platelet donation in Australia was just starting when I moved to UK and then got put on hypertension mediation, so no more donation for me after 15 years or so. if I was still donating I'd do platelets now.
posted by Logophiliac at 12:16 PM on March 1, 2010