How much blood do we have?

Last week a friend, through a freeky accident, lost a lot of blood. When he went to the emergency room they said his hemoglobin was 5.17. It didn’t seem to be critically serious because they waited two hours before they actually gave him a transfusion of what was eventually four bags. He was still fairly lucid (could say his SSN and address, etc.), but said the ceiling tiles were in pink and green three dimensional figures and when he closed his eyes he saw extremely colorful and detailed figures, sort of like a motion picture. He claims he could even zoom in on a molecular level. It got me to wondering how much blood we do have and how much we can afford to lose before it is curtains. And since they didn’t seem to be in a hurry, how low would that hemoglobin have to go before they were? By the way, he said it was extremely unpleasant: extememe weakness, nausea, vertigo, said hallunications, muscle spasms, splitting head pains, and generally feeling terrible, which still lingers now, a week later. So I’ve decided the wrist slicing option is totally out for me, should I ever be so inclined.

Adult males 12 pints, adult females 9.


A rule of thumb I once heared was about UK 1 pint (20 ounces) per stone wieght (thats 14 pounds to most of you.) I would not say I would trust the accuracy of the source but does seem to be ball-park compatible with Ice Wolf

I know where the 3 pints go!! :D:D:D

The standard answer to blood volume from most of my reference books is:

adults - 70 ml/kg
children - 80 ml/kg
infants - 90 ml/kg

Normal haemoglobin values range from 13 to 18 in a healthy adult. So a value of 5.17 clearly shows someone with only about one third of what he should have.

The two hour wait before infusing blood may have been due to delays with the laboratory: blood typing, matching, availability of type etc. (Hopefully someone more knowledgeable will contribute a post on this detail).

Basically, he suffered what we call in the trade, hypovolaemic shock - the shock state caused by a lack of circulating blood volume. The first problem with reduced volume is a reduced level of haemoglobin, which transports oxygen from the lungs to the cells. Hence, the body’s tissues are starved of the oxygen they need to produce adequate amounts of energy to stay alive, let alone function properly.

In addition to hypoxia, lack of blood volume results in reduced blood pressure, which in turn means that less blood is pumped to the brain and other vital organs. So the symptoms described match those of a person whose organs are simply not getting the oxygen or nutrient they need to function properly.

Incidentally, while your friend may not have got blood immediately, I’ll bet he got some intravenous fluid very soon after presenting to the emergency room. This helps to increase blood pressure so that the remaining haemoglobin can do its job until more is either introduced intravenously, or made by the body’s bone marrow.

You might want to look atThis Site On Exsanguinating. This is what was slowly happening, it sounds like. I’m very glad that he was transfused and pulled through okay :slight_smile:

My mother spoke to me about this. She’s witnessed one death by exsanguination. She said it’s surreal to see, the volume of blood that a body has.

I hope your friend makes a full recovery.


Er,…Her Highness has roughly nine pints. Unless, of course, Her Highness would like some more, in which case I could have someone bled for Her Highness.


Hi DVous. Thanks for the detailed answer. Yes, he did get some fluid about 1 hour after he arrived in Emergency. I suggested the nurse ask the dr to draw his blood because they sent in three plebotomists and they couldn’t find a vein for 45 minutes and they kept sticking needles into him. It seemed cruel. But they totally refused to call the dr to do it. They also made him stand and get on and off a table for x-rays, which he doesn’t remember well. I’m a layman, but it seems they didn’t read the symptoms accurately, from what you say, because once they had the hemoglobin level they became more concerned. His eyes were swollen and he was white and limp. But you just have this trust in medical people that is hard to overcome. When they released him his hemoglobin had been 10 for 24 hours. I am now feeling this anger that it wasn’t handled well, but maybe that’s just because I don’t know enough about this type of situation. He wasn’t bleeding when he went in and he was coherent. Maybe that was misleading. Well, I guess we’ll just go on from here and not dwell on it.

In general, the phlebotomist is the one you want poking you, not the doctor. Phlebotomists are highly trained and very experienced in that area. Doctors usually less experienced at drawing blood–they do it less often because the phlebotomist does it.

Also, it is entirely possible that the available doctor was an idiot, and the phlebotomists were trying to protect your friend!

Glad he is okay.

Not to take away from the answer given by DVous means that makes the essential points…

Females have less hemoglobin than males, between 11.5-15.5 vs. 13.5-18.5; possibly due to menstruation, blood becoming dilute during pregnancy, etc. Of course, this does not apply to your friend.

Most people would use 70mL/kg as a rough estimate of blood volume. This is probably equivalent to what ticker said.

Having a low hemoglobin, “being anemic”, has many causes which can be teased out depending on the size and colour of the blood cells. These include bleeding, chronic diseases, iron deficiency, vitamin B12 and folate deficiency, thalassemias, sickle cell, sideroblastic anemias, etc. Having excess “water” in your blood from being pregnant or drinking too much also causes a lower hemoglobin even though the amount itself has not changed.

A young person could probably lose 15% of their blood with no real symptoms. Ftrom 10-20% of blood loss, the blood pressure would start to fall (the systolic blood pressure, the hih number would fall; the lower diastolic number would probably start to rise. To maintain perfusion, the heart rate would then increase. This would be dramatic after a blood loss of 30% or so, and is sometimes referred to as “stage III shock” when bleeding is present.

Anemic and shocky people both complain of dizzy or light-headedness, fatigue, difficulty breathing (if severe), difficulty peeing (if very severe), and so forth. The first step is usually to give them saline to expand the blood volume and restore the pressure. One gives blood if the hemoglobin is low and they are symptomatic; since hepatitis is scary one tries to avoid giving blood if possible.

If the nurse and phlebotomist can’t get the vein after 45 minutes, I doubt that I could either. Green Bean is right. On the other hand, doctors are occasionally more willing to try different veins and this can be fruitful.

Green bean is right and the phlebotomists and IV teams have much more experience poking and prodding than your average doctor. Of course, if it was as difficult as you say they should have considered a local anesthetic. I also find doctors are generally more willing than phlebotomists and nurses to try “unusual” (i.e. leg) veins in difficult cases.

Amazing & possibly sickening factoid:

The average adult male has about six quarts of blood, women slightly less, children considerably less. Thus, if we estimate that on average each of the approximately 6 billion people in the world has about one gallon of blood, we get about 6 billion gallons of blood in the world.

Since there are about 7.5 gallons per cubic foot, there are approximately 800 million cubit feet of blood in the world.

The cube root of 800 million is about 928. Thus, all the blood in the world would fit into a cube 928 feet on a side - about 1/200[sup]th[/sup] of a cubic mile!

I knew you’d be amazed.

Or sickened.