human body blood

[harley06]

How much blood does the human body contain

[ugly_bob]

approximately 8 pints, depends on the person.

[Catso]

I still remember a huge argument with someone at school (30 years ago now!) who steadfastly maintained it was 8 gallons. He just wouldn't have it that it was 8 pints.

As I pointed out at the time 'how much would 8 gallons of blood weigh, then?'.

[boobesque]

i thought it was 4 decimeters

[shammydodger]

Ugly bob is correct. It depends on the size of the person. The eight pint figure is an average. And, after 30-odd years of McDonalds etc, probably a minimum.

[Catso]

I don't think the amount of fat on a body makes that much difference. It's the underlying framework: big body - more blood; small body - less blood.

[theprof]

In both medicine and the biochemical sciences, total human blood volume is normally calculated on the basis that we have 70ml of blood for every kg we weigh. This provides a close enough approximation for most purposes.

There are more accurate formulae avalable to calculate blood volume when the need arises. These formulae are now being increasingly used by physicians during certain types of oncology drug monotherapy, where excess dosage could be fatal.

For men the formula is:

Blood volume = (46.7 x weight in kg) + 1742

For women, the formula is:

Blood volume = (53.7 x weight in kg) + 984

It should be noted that these formulae only apply to adults. Different formulae are needed when the blood volume of babies and children need to be calculated. Baby and children formulae are more complex than the above and not quite so reliable.

Another rough method of calculation used in the past is that blood volume is around 8% of total body weight in babies, children and adults. Some countries find it more convenient to calculate blood volume based on skin surface area, but the result is not as reliable

All the same, because it always comes back to body weight, Catso is absolutely right that the heavier the person, the more blood he/she contains. Body size cannot always be attributed to obesity and there is no statistical correlation between the lipids (fats) in the human body and blood volume.

[theprof]

I should have explained that the results of the blood volume formulae I discussed above provides the blood volume in millilitres.

As an example, in the case of a 70kg man, it would be 5011ml, which is slightly in excess of the 4900ml figure derived from the 70ml per kg generalisation.