Buzz
Blood. The mere mention of it can cause fainting for hemophobics, or those with an extreme fear of the sight of it. On the other hand, the fear might be justified: Blood transports vital nutrients within us, supplies oxygen, and defends against infections. Keeping it safely contained within our veins and arteries is ideal, and losing it understandably causes distress.
So, how much blood does an average adult carry? And how much can they afford to lose without serious consequences?
For a tangible comparison, visit the dairy section at your local grocery store and grab a gallon of milk. That’s about the same amount of blood circulating in your body at any given time.
More precisely, it ranges from 1.2 to 1.5 gallons, as Dr. Daniel Landau, a hematologist and oncologist, shared with LiveScience in 2016. For some adults, this is roughly eight to ten percent of their body weight, and this blood volume remains constant after about the age of 6. Babies, however, carry much less—around a cup, which is roughly the same amount as your average cat.
If you lose some of that, your body begins to feel the difference. That 1.2 to 1.5 gallons translates to 4.5 to 5.5 liters. Blood donors typically give around one pint, or half a liter, without any serious consequences. But if an accident or injury causes you to lose three to four pints, you’re facing a Class 3 hemorrhage and will need a blood transfusion. Losing more can prevent your heart from maintaining blood pressure. (The reason we turn pale during blood loss is that the body tries to restrict blood flow to vital organs using vasoconstriction.)
A person weighing 200 pounds will carry significantly more blood than someone who weighs 100 pounds and could theoretically lose more blood without approaching life-threatening levels. However, scientists have pointed out that blood volume isn’t directly proportional to body weight and can be influenced by the amount of lean tissue versus fat. This impacts the vascular system.
Using an online blood volume calculator, it’s estimated that André the Giant, who weighed around 525 pounds, may have carried as much as 21 liters of blood—four times more than an average person, not accounting for variations in body fat. While that’s quite remarkable, André wasn’t the largest of mammals, despite what his promoters claimed. For perspective, a blue whale’s 400-pound heart circulates 220 liters of blood throughout its enormous body, which is approximately 58 gallons.
