Thyroid UK
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Meaning of my Blood Test Results

I had a blood test on 2nd March. A number of the results had exclamation marks.

Can anyone please tell me what they mean? Thanks.

!  Red blood cell (RBC) count.  4. 15.  10*12L.      (4. 20 - 5.70)

!  Mean corpuscular volume (MCV).    100.8 fL.   (80.0 - 99.0)

! Immature reticulocyte fraction          0.4  ratio     < 0.30

4 Replies


Results are flagged because they are below or over normal ranges.

Low RBC and high MCV can indicate low iron, low B12 or low folate.  Other reasons are outlined in

This link explains reticulocytes


I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.


Thank you for your help.

I am not surprised that I now have low vitamin B and iron after my thyroxine being cut from 200mcg to 125mcg daily by a new doctor. No matter how often I say that I don't feel the same on the lower dosage, he steadfastly refuses to up it.

Basically, I am in good health, but I feel that the situation has left me to self medicate with supplements. I understand about taking vitamin B12 tablets under the tongue, but I am not sure of what dosage to take as an iron supplement. 

I would be most grateful for any advice.


Try not to worry too much about the levels if they are a one off. I have had a few fluctuating levels over the years but they come right back into range by the next test. I have also shown to be on the border of mild anemia for 3 years now so although this flags up, it is just me and my RBC count is consistent.



I said that the results could indicate low iron and low B12.  Ask your GP to test ferritin, B12 and folate to confirm whether they are low before you supplement.

Reducing Levothyroxine dose won't cause low B12 or iron.


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