Anemia is a condition when your body doesn't have enough healthy red blood cells. Red blood cells are important because they carry oxygen around your body. If your body doesn't have enough red blood cells, it can't get enough oxygen, so you can feel tire and weak. Normally, red blood cells are made in your bone marrow - the soft stuff at the center of your bones. It can sometimes happen that your body doesn't make enough red blood cells though, and that's what we call anemia. Anemia is treatable, but it's important to understand what’s causing it first.