Learn what different shades of blood mean and how they signal changes in your health or potential medical issues.

REM stages and one REM stage. Ideally, you repeatedly cycle through each stage. Learn how long each stage lasts.

Scientists have discovered how aging blood stem cells acquire mutations that give them a growth edge, creating fertile ground for the development of clonol hematopoiesis, a condition that dramatically ...

A new study published in The Lancet Planetary Health suggests a changing climate threatens the continuous availability of safe blood across the world.

Extreme weather disasters, increasing as the planet warms, can curb blood donations while increasing demand, a new analysis ...