Iron deficiency anemia is diagnosed via CBC showing low hemoglobin or red blood cell count, and potentially low MCV (<85 or <80).

“you will see that on a CBC the complete blood count you will likely be anemic which means your hemoglobin or red blood cell count will be low the MCV the mean chloropuscular volume of your red blood cells may be low less than 85 or even less than 80 giving you a microcytic anemia”