Donating Blood and being tired
 

After you donate blood, what actually causes you to be tired and sleepy? Yesterday I donated a pint and came home and passed out. Not like fell unconcious, but I slept for a good 7 hours.

What exactly causes that? I mean obviously the blood loss, but what in that makes you lethargic and sleepy?

Actually, i'm usually fine after donating blood.

I remember having a training session after donating blood. But aside from the comment of "you're slower today," my coach didn't mention much. Until I told him that I donated blood that day; then he was kind of angry at me.

The main thing probably is the loss of blood. People who are anemic (low iron count) are constantly tired. It is possible that after donating blood, your iron count has gone way down causing you to be tired. But i'm no doctor, so don't take my word on it.

Let's look at this item-by-item.

First, your blood carries oxygen, so if you have less blood, it takes longer to carry the same amount of oxygen.

Next, when you are short of blood, which is life, your body begins furiously making more blood to replace what was lost. This is hard work and is also a priority to your body, so other parts of your body sacrifice to make that blood. A correlation is why people get frostbite when in the cold, besides exposing fingers and toes to the cold. Your body sends blood to protect your vital organs. That means less warming blood is around the toes and hands, so they get colder than the rest of your body. Same thing when you bike...the body sends more blood to the legs which makes it tough to immediately do something else when you finish biking until you get the blood moving back to other areas.

I'm sure someone out there has more or will correct me if I'm wrong on something here!

I had to stop giving blood because I became anaemic (stupid body not replacing lost blood fast enough) but I never got that tired after a donation. Maybe you were a bit stressed by it, stress can make you sleepy when the adrenaline wears off.
Take it easy and if it happens again when you give blood, consider stopping. It's not worth it to risk your own health.

Well, it wasn't really a problem. I was able to finish my day and all that, I just got really tired (I didn't eat very well after giving blood, which was the problem) but I was just wondering the more scientific reasons behind what made you so sleepy after giving blood.

It won't stop me in the future or anything, it's not really that big of a deal to me.

For me, it always varies from time to time--sometimes I get really really tired afterwards, sometimes I don't.

I also usually make sure to boost my iron content for the few days before and after I donate. It seems to help.

I'm fast approaching my 5th gallon. Only once did I feel strange afterward. I love to drink later in the day, and get totally drunk on 3 beers! What a cool feeling (I guess).

You were probably tired already, but just didn't know it. 7 straight hours of sleep, oh what I would give for that!

I'm just over three gallons. I second this, absorb... I'm a VERY cheap date the night after giving blood! And since there's not very much alcohol actually involved, it metabolizes off fast. I can go from totally shitfaced to stone sober in about half an hour.

The loss of blood does put the body into overdrive to replace it. Also, you've lost a pint of fluids straight out of your arm, so dehydration is always somethign to watch out for. The cup of juice they give you in the recovery are is completely insufficient--I come home and drink at least half a gallon of water by the end of that day.

I know that donating plasma is a bit different than blood, but I cant do either anymore.

I used to donate plasma often, but it started making me really sick., no matter what I would do before hand. The last time I donated plasma, On the way home we puled off so I could use the restroom. The next thing I know it's several hours later, and I am in the hospital. Apparently I had gone in the bathroom and passed out stone cold, busting my head on the cement floor. I had a nice little concussion. I was awake, but saying all this weird stuff, so my boyfriend took me to the hospital. I dont remember any of it.