The RDW stands for Random Distribution of red cell Width. This value tells how consistent are the size of the red blood cells. Newly made cells (reticulocytes), B12 and folic acid deficient cells are larger than iron deficient cells. This is an electronic index that may help clarify if an anemia has multiple components. The high RDW helps determine if there is only a B12 and/or folic acid deficiency (with normal RDW showing the red cells are mostly the same size) or with concomitant iron deficiency (a high RDW due to small and large red blood cells).
Red cell distribution width (RDW) is a calculation of the variation in the size of your RBCs. In some anaemias, such as iron deficiency or pernicious anaemia, the amount of variation (anisocytosis) in RBC size (along with variation in shape – poikilocytosis) causes an increase in the RDW.
My son had Microcytic aneamia last year. His Hb was low normal, ferritin low but his MCV's were low meaning his blood cells were on the small side which meant his symptoms of aneamia were massively exaggerated . It took 12 weeks for diagnosis though, even though he went through A&E 3 times with breathlessness .
Microcytic aneamia can be caused by Copper deficiency as well
Jessie, did it take 12 weeks because they couldn't distinguish which he had? There is a B6 (pyridoxal 5 phosphate) component which makes me wonder if that would be a better supplement than iron. I don't know though.
What did they prescribe for your son and is he well?
No, it took them 12 weeks because we have a bunch of idiots at our local (one of the biggest teaching hospitals) hospital who were so convinced he was suffering anxiety due to my obsessiveness over his health that they and they refused to test his ferritin because at his age 'he couldn't be aneamic'.
it was a cardiologist who eventually decided he was aneamic and within a few weeks on iron he was right as rain. I might add, I had queried the low McV count with the Endo for over a year to be told it was nothing to worry about. Once on treatment it took a further 6 months for his blood count and thyroid to come back to normal (even his goiter has gone ) he has entered puberty and grown a lot in height and shoe size. the Endo has only just admitted he had Microcytic aneamia and we at last have it in writing.
As I said I think it was more than iron and I have him on Bcomplex in a muti and B12 along with minerals which I add to his drink .
He was born with hemolytic aneamia which in my opinion left him less than optimal in some neutrients .
I wonder if the B6 should be pyridoxal 5-phosphate which is an active form of B6. I know it is said the a deficiency is unusual but I know it's been used for "morning sickness" and carpal tunnel which many people suffer so it makes me wonder.
I'm glad you persevered and your son is doing well.
I've never managed to work out why my RDW is the value it is.
I've had it measured 5 times. The first 4 times it was high in range or over the range, getting higher with each measurement. I was suffering from low iron but over the time period I got these increasing RDW results my iron was getting better.
Then between the 4th and 5th measurement I started supplementing with high dose methylcobalamin despite having very high levels of serum B12. (I had good reasons for doing so, and it was an experiment.) I also took modest amounts of methylfolate.
The 5th time my RDW was measured it had dropped into the lowest quarter of the range. My B12 was high as usual, my folate was fine, and I was no longer short of iron. As usual I don't understand why my RDW is the level it is.
The RDW stands for Random Distribution of red cell Width. This value tells how consistent are the size of the red blood cells. Newly made cells (reticulocytes), B12 and folic acid deficient cells are larger than iron deficient cells. This is an electronic index that may help clarify if an anemia has multiple components. The high RDW helps determine if there is only a B12 and/or folic acid deficiency (with normal RDW showing the red cells are mostly the same size) or with concomitant iron deficiency (a high RDW due to small and large red blood cells).
Optimal Range: 13
The RDW is often increased in:
B12 and Pernicious anemia
Folic acid anemia
Iron deficiency anemia combined with other anemia
Hemolytic anemia
Transfusions
Sideroblastic anemia
Alcohol abuse
Various less common and hereditary anemias
The RDW is often decreased in:
Iron deficiency anemia (blood loss, parasites, poor iron absorption, etc.)
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Anemia and supplementation 
Microcytic, hypochromic anemia.
How can I get a diagnosis when my symptoms could be caused by so many conditions?
Husband's blood results - hashimoto's apparently stable
