Firstly, you need to remember what the RBCs are, what their componments are and how erythropoiesis is done. You should know how bone marrow, hemoglobin, vitamine B12, folic acid, iron and the kidneys...
Follow your heart! It's quite simple. Nursing might be a tough job, however, you will realize that you won't be the same guy as you were before, but a new person, with new dreams and expectations....