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.

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 ...

As we age, blood stem cells, the essential source of new blood cells in the body, can accumulate genetic mutations. These ...