Anemia is a condition that happens when there are not enough red blood cells in your body.
Red blood cells carry oxygen through your blood, giving you energy and helping your muscles, bones and organs work properly.
The oxygen that we breathe in passes through our lungs and into the red blood cells.
In anemia, there are not enough red blood cells to carry this oxygen around the body.
Anemia can make you feel weak and tired because you are not getting the energy you need.