Blood looks simple — a red liquid under your skin. Up close, it's one of the most
remarkable systems in the human body: a moving organ that feeds every cell, fights
every infection, and seals every wound. Tap through the flashcards below and see how
much you already know.
0 of 12 facts explored
Test what you know
Tap a card to reveal the answer
Who can you help — and who can help you?
Choose a blood type to see its matches
Can donate to
O-O+A-A+B-B+AB-AB+
Can receive from
O-
O negative is the universal donor — safe for almost any patient in an emergency.
Blood, by the numbers
How much blood do you carry?
Blood makes up about 7–8% of body weight. Enter yours to estimate.
kg
Enter your weight to see your estimate.
19,000 km a day
That's how far your blood travels every single day, pushed continuously by your
heart — about 19 round trips between Chennai and Coimbatore, without ever stopping
for a break.
1 donation, 3 lives
A single donation is separated into red cells, plasma, and platelets, each one
going to a different patient who needs it.
Bonus fact
Newborn baby ~1 cup
Adult ~35 cups
Now you know what's inside. Ready to share it?
Every donation is up to 3 lives waiting for a match.
