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Collapsed after just 40ml bloodloss

Today a colleague asked if I could donate some blood for an experiment. I said no problem and had 10 tubes of 4ml blood each taken. I have no problems with needles and am definitely not squeamish. I have had many blood tests in the past of similar or even higher volumes and have been fine. However today after just 40ml I felt light headed and collapsed, does anybody know of any reason why this could be?

I don't remember anything of the incident, I just woke up with a friend shoving a drink in my face, and am curious (and a little embarrassed) to find out why this could have happened. Is it ever normal to loose such a small amount of blood but have such a response?

Thanks
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 That is certainly not a negligible amount of blood to be drawn. It would be easy to collapse after rising too quickly, especially under stress, without having eaten recently, being especially tired otherwise, recently exercised, are overweight, etc etc. I wouldn't worry about it. Perhaps keep an eye out for excessive light-headedness, sleepiness, or trouble breathing. If you're going to worry about it anyway, its not a big deal to just get a check-up (have your blood pressure checked, etc) and ask your doctor.
 You became vagal. Your heart rate slowed to a point it was not able to sustain a blood pressure. This would be especially evident if you had not had anything to drink for some time as dehydration would augment the effect. When blood is drawn for a prolonged period of time it is best to be lying flat and to get up slowly afterwards.

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Collapsed after just 40ml bloodloss

 Quote by imsmooth You became vagal. Your heart rate slowed to a point it was not able to sustain a blood pressure. This would be especially evident if you had not had anything to drink for some time as dehydration would augment the effect. When blood is drawn for a prolonged period of time it is best to be lying flat and to get up slowly afterwards.
+1

How long had it been since you ate or drank Ryan?
 Recognitions: Gold Member Just to sort of confirming what others have said, I understand from my wife who takes blood samples all day long that it is quite normal for young men to pass out in the process and that sitting or lying down is required before they start taking samples.
 Mentor Blog Entries: 1 Ah yes I did skip breakfast and am not sure if I had much to drink in the morning. The internet was providing me with all sorts of bizarre answers but it's good to know theres a simple reason. Thanks for your responses everyone!

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 Quote by ryan_m_b Ah yes I did skip breakfast and am not sure if I had much to drink in the morning. The internet was providing me with all sorts of bizarre answers but it's good to know theres a simple reason. Thanks for your responses everyone!
In the words of the great philosopher Cousin Eddy; "Bingo"

Thus far in med school, I've watched 3 peers pass out from minor nicks from the scalpel blade. The first instructor on the scene always says--Did you eat breakfast? The answer has always been "no".

We've also watched 2 peers faint during postmortems, where they had to stand up in front of the class and go toe to toe with a bunch of stodgy old MDs and PhDs--The question again comes back to food, particularly breakfast.

We lost another 4 all in the same day to blood donations, again not eating and drinking enough.

Med students, because of our overwhelming boring study-lives, have a tendency to skip that most important meal of the day and to generally not take such good care of ourselves in our stress-induced study mania.

But we're not, as you demonstrate , the only ones in that boat. When you blood sugar is low or when you are dehydrated, minor blood loss brings on the "woozy", tunnel-vision, "Hi, meet the floor"-experience in us all.

You can probably thank evolution for doing a half-*** job of making us bipedal (and while your griping to the big E, give a shout out for back pain as well )

In the future, just make sure you fuel yourself up before parting with that precious red stuff, or alternatively give yourself ample time to rise from a laying-to-seated-to-standing position and you'll not have to worry about insults to your manliness,

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 Quote by bobze In the words of the great philosopher Cousin Eddy; "Bingo" Thus far in med school, I've watched 3 peers pass out from minor nicks from the scalpel blade. The first instructor on the scene always says--Did you eat breakfast? The answer has always been "no". We've also watched 2 peers faint during postmortems, where they had to stand up in front of the class and go toe to toe with a bunch of stodgy old MDs and PhDs--The question again comes back to food, particularly breakfast. We lost another 4 all in the same day to blood donations, again not eating and drinking enough. Med students, because of our overwhelming boring study-lives, have a tendency to skip that most important meal of the day and to generally not take such good care of ourselves in our stress-induced study mania. But we're not, as you demonstrate , the only ones in that boat. When you blood sugar is low or when you are dehydrated, minor blood loss brings on the "woozy", tunnel-vision, "Hi, meet the floor"-experience in us all. You can probably thank evolution for doing a half-*** job of making us bipedal (and while your griping to the big E, give a shout out for back pain as well ) In the future, just make sure you fuel yourself up before parting with that precious red stuff, or alternatively give yourself ample time to rise from a laying-to-seated-to-standing position and you'll not have to worry about insults to your manliness,
Thanks, that does make me feel a lot better! Typical male pride but I've adamantly insisted to my colleagues that needles and blood don't scare me and that I (in spite of jokes my boss clearly heard) did not collapse at the sight of a needle.
 Could that also be an effect of habituation? I didn't eat all day since waking up, only drank about a liter of coca cola over the course of the day (~440 kcal as pure sugar), worked and then went to donate blood plasma. I gave 850ml plasma and also around 50ml full blood for all the blood tests, I have low blood pressure (102 / 53 before the donation), and I didn't feel any different than before. Yeah I know I shouldn't give blood in this state, but I need the $$. I also have low blood sugar in general. However I basically never eat breakfast and live through the day on coca cola and eat only small amounts in the evening. I donate regularly and never fainted in my whole 27 years of life at anything. Is there a medical explanation for that?  Could that also be an effect of habituation? I didn't eat all day since waking up, only drank about a liter of coca cola over the course of the day (~440 kcal as pure sugar), worked and then went to donate blood plasma. I gave 850ml plasma and also around 50ml full blood for all the blood tests, I have low blood pressure (102 / 53 before the donation), and I didn't feel any different than before. Yeah I know I shouldn't give blood in this state, but I need the$$\$. I also have low blood sugar in general. However I basically never eat breakfast and live through the day on coca cola and eat only small amounts in the evening. I donate regularly and never fainted in my whole 27 years of life at anything. Is there a medical explanation for that?
 Recognitions: Gold Member In Argentina at least when you have to pass a blood analysis the doctor tells you to come early in the morning without having drink/ate anything. Out of the 3 times I've had extracted blood, I became vagal 2 times. They extract approximately 50 ml I think just like in the case of the OP. About SamirS who said "I gave 850ml plasma and also around 50ml full blood for all the blood tests"... wow. Did you know there is approximately 5 liters of blood in our body? You gave around 20% of your total blood, that's insane to me.
 There's a table how much blood plasma you can donate in one session, and for me (>79.9 kg) it's 850ml of plasma in one session. The real funny part ist, people can do that again after just two days passed! Up to 45 times a year. Blood plasma is just the watery part in which the cells are suspended. It is useful for replacing volume and for the extraction of clotting factors.

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