With iron deficiency, the red cells usually appear small and pale on a blood smear (microcytic and hypochromic red cells). Therefore, this finding strongly suggests iron deficiency even if anaemia is not yet present. Examining a blood smear is a useful way of screening for iron deficiency. Children with iron deficiency also have a low serum concentration of ferritin. This will prove the diagnosis. With severe iron deficiency the child will develop anaemia. The haemoglobin concentration is usually normal with mild iron deficiency.