A reduction in the hemoglobin of red blood cells with consequent dificiency of oxygen, leading to weakness and pallor. (Real dictionary definition)

anemia is when you don't have alot of iron in your blood.
usually when you have anemia you take 2 pills everyday and you can get tired easily even if you have 9 hours of sleep already.but that's only if you don't take your pills.
and sometimes your doctor will put you on a special diet to make you get more iron in your blood.

as opposed to the medical bullshit basically means always fuckin tired,