Boots WebMD Partners in Health
Return To Boots

Picture of blood

We probably don’t think about blood much, unless we cut ourselves or have to go for a blood test.

Most adults have around five litres of blood. That's more than a gallon. Blood does vital tasks around the clock, circulating around the body delivering oxygen and nutrition where it is needed and removing waste.

Blood flows through blood vessels, the arteries and veins, in the body.

Blood carries important cells and proteins as well as plasma. Plasma makes up about half of the volume of blood and carries proteins to help the blood clot, glucose and other nutrients.

Illustration of blood

About half of blood volume is composed of blood cells:

  • Red blood cells, which carry oxygen to the tissues
  • White blood cells, which fight infections
  • Platelets, smaller cells that help blood to clot

WebMD Medical Reference

Stay informed

Sign up for BootsWebMD's free newsletters.
Sign Up Now!

Popular slideshows & tools on BootsWebMD

mature woman
Go for the glow!
avacado on whole wheat crackers
Plenty of healthy options
bowl of soup
Small changes that lead to weight loss
baby eating from spoon
What to feed your baby in the first year
cold sore
How to cope with cold sores
toddler doodling
What to expect in your child's second year
bain illustration
Best foods for your brain
bucket with cleaning supplies in it
Cleaning for a healthy home
mother and child
Could your baby be allergic to milk?
cute baby
Simple tips to keep baby's skin healthy