Hello and welcome to health care magic.
When a FBC is done the doctor usually looks at the red blood cells and
haemoglobin, the white cell count (WBC) and the
platelet count first then looks at the other parts of the results which give additional information about the former.
A full blood count can done a routine check up or a follow to check the result of certain treatments. It can also be done if you had presented to your doctor with symptoms related to
anemia, infection, inflammation, excessive bleeding or difficulty or excess clotting or symptoms suggestive of malignancy.
Usually when a doctor asks for folate,
vitamin B12 and
thyroid after a full blood count it is usually because the haemoglobin may have low suggesting anemia ( low red cell mass- the red cells transport oxygen to different parts of the body.
When a
blood test indicates anemia the doctor then has to determine the type and cause of the anemia. The rest of the blood count can give you an idea of both.
The MCV ( mean corpusular volume) tells the average volume of the red blood cell.
The MCH ( mean corpusular haemoglobin) tells you the average amount of heamoglobin in the red blood cell.
Normally the doctor will look at the two: when they are high it may indicate vitamin B12 or
folate deficiency which is why the doctor may suggest these be done.
I hope this information is helpful to you.
You should speak to your doctor regarding any other concerns