I wonder if anyone can help me to understand this whole anaemia business because I am deeply confused!
I had the FBC done a few months ago, and the GP called me and told me that I was not anaemic but my red blood cells were slightly enlarged so they were going to test B12 and folate. Subsequently my B12 was found to be low and I was started on loading doses.
I understand that I had a high MCV ( macrocytosis). My haemoglobin was high normal. So this is where I get confused!
Is there a difference between macrocytosis and macrocytic anaemia? Is megaloblastic anaemia different again? Was the GP just referring to my haemoglobin levels when he said I wasn't anaemic?
My understanding is that B12 deficiency typically presents with high haemoglobin. Is that correct? Would this obscure any iron deficiency anaemia present or would that lead to no diagnosis (mixed anaemia meaning normal MCV and haemoglobin)? My ferritin was not tested.
Finally, is it "anaemia" that leads to shortness of breath, dizziness, palpitations and tiredness or would it happen anyway because of the deficiency? What do they mean by anaemia here? Am I "anaemic"?
Help!
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Curlygal
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I would think that when your GP referred to 'anaemia' they meant iron deficiency anaemia. This presents with low haemoglobin, and/or low ferritin, and sometimes smaller red blood cells.
B12 deficiency can cause macrocytosis/macrocytic anaemia - enlarged blood cells. Pernicious anaemia is a term given to a specific inability to absorb B12 via the digestive system leading to B12 deficiency, but there may be other causes of B12 deficiency. All except dietary deficiency are treated with B12.
So you probably don't have iron deficiency anaemia (though you'd need to know your ferritin level to be certain).
Iron deficiency anaemia, as well as B12 deficiency and pernicious anaemia, can cause the symptoms you list.
Your doctor is probably just being technical based on this definition: "Anemia, the condition of having less than the normal number of red blood cells or less than the normal quantity of hemoglobin in the blood."
As you are probably aware, there are different classifications of anemias. This page has some info on it: labpedia.net/test/259
Because cytometric parameters are more easily and less expensively measured than are erythrokinetic and biochemical ones, it is most practical to work from the cytometric classification, to the erythrokinetic, and then (hopefully) to the biochemical. Your first job in working up a patient with anemia is to place the case in one of three major cytometric categories:
Normochromic, normocytic anemia (normal MCHC, normal MCV).
These include:
-anemias of chronic disease
-hemolytic anemias (those characterized by accelerated destruction of rbc's)
-anemia of acute hemorrhage
-aplastic anemias (those characterized by disappearance of rbc precursors from the marrow)
Normochromic, macrocytic anemia (normal MCHC, high MCV).
These include:
-vitamin B12 deficiency
-folate deficiency"
I will say that, as useful as these parameters are, some of us are just oddballs. If my blood were to be given a classification it would actually be hypochromic, normocytic. Go figure.
Next time you see your GP ask him very politely to explain the terms and levels so you can understand.
Anaemia basically is a lack of sufficient haemoglobin to carry adequate oxygen to the body.
It can be microcytic with small red cells, usually because of iron deficiency, or macrocytic with large red cells, usually because of Folate or B 12 deficiency.
Even if there is no anaemia the blood film may still show microcytes, microcytosis, or macrocytes, macrocytosis.
Megalocytes are the same as macrocytes.
Megaloblasts are immature megalocytes, megaloblastosis is the word used to describe this.
Anaemia can cause all of the symptoms you describe, but equally B12 deficiency, with or without anaemia, can cause all of the symptoms associated with anaemia. In addition it can cause other symptoms, including neurological symptoms which require proper prompt treatment, regardless of the presence of anaemia, as they may be irreversible.
The normal range for B12 levels is almost certainly too low as symptoms can occur not infrequently with levels of up to 500.
The GP should always treat the patient and not the lab results which merely steer him towards a correct diagnosis.
Sadly most GPs seem to be unaware of the complexity of these issues and if in doubt tend to dismiss the patient's symptoms or treat them inadequately and without the necessary urgency.
sorry but I thought the definition of anaemia is a blood disorder - of which there are many - including microcytic anaemias (in which red blood cells will be smaller and is typical of an iron based anaemia), macrocytic/megaloblastic anaemias/macrocytisis (in which red blood cells are larger and rounder than normal) and there are whole host of variations of size and shape relating to red blood cells. The common factor is that the distortion makes the red blood cells less efficient at transporting oxygen from the lungs to cells where it is needed.
However, also true that the symptoms mentioned by curlygal can be caused by B12 deficiency without the obvious presence of any particular form of anaemia.
I understand what you say about the distortion in the blood cell shape, another example would be sickle cell anaemia, where the cell is crescent shaped?
Thanks for all of the replies! I'm not sure I'll ever fully understand this (gave up biology at 14! Major fail as I now have two different blood disorders 😬) but I am clearer than I was. Many thanks ☺
My old pathology text book defines Anaemia as "a deficiency in quality or quantity of erythrocytes (red blood cells)" in the circulating blood. The characteristics of the cells merely helps determine the cause of the anaemia. Abnormal blood cells will generally be less able to carry oxygen to the tissues. This is a function of haemoglobin, so in Anaemia the haemoglobin will be lower than normal.
The name is derived from Ancient Greek: ἀναιμία anaimia, meaning "lack of blood", from ἀν- an-, "not" and αἷμα haima, "blood".
Whereas many both within and without the medical professions seem to think of it as exclusively iron deficiency.
Perhaps would be better if we used iron-specific terms, possibly based on Greek σίδηρος (sídiros), for iron deficiency - but that isn't going to happen any time soon.
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? Pernicious anaemia with normal B12 and no anaemia?
Vitamin b12 vitamin b9 anaemia
Iron deficiency anaemia 
Could I have Pernicious Anaemia?
