 In the era before automated blood counting was available everywhere. Hematologists used to get very upset by physicians transfusing their patients before consulting them. However, that is a thing of the past now. And you can go ahead and transfuse. What that might do will be to mask the true state of a patient's blood cell indices. So if somebody had microcytic anemia and was transfused with normalcytic cells, then the automated blood count may give you a normal MCV. However, when you look at the distribution curve, you will be able to recognize clearly two populations. That way you will not be deceived by the average, the number. It's always important to look at the distribution curve in all instances. Don't focus on the averages beyond necessary.