Pernicious Anaemia Society
15,502 members10,915 posts

Little bit puzzled by drs theory !

Hey guys quick question, my dr said anaemia takes ages to develop so there is no way my full blood count would be any different from 6 months ago... is this true ? as why would my b12 have dropped so quickly in 6 months but my FBC wouldn't have changed.? Both drs I saw were convinced they didn't need to test anything else because of that alone. Is it likely I have PA with a count of 162? I eat well so I don't know what it could be, thank u in advance xx

7 Replies

Anaemia would take several months to manifest as it would be healthy blood cells being replaced with cells that are deformed because there isn't enough B12 to mediate healthy production. Red blood cells live for about 4 months so it would take months

However, both doctors appear to be rather confused about the relationship between macrocytosis and B12 deficiency. macrocytosis is a symptom of B12 deficiency not a cause (though it may be involved in some of the other symptoms. Also, it isn't necessarily among the first symptoms to appear - in 30% of patients (at least) - neurological symptoms develop first.

B12 is used by a lot of processes in the body - making healthy red blood cells is one of those processes, maintaining the insulating lining around nerve cells is another, the processes that release energy in your cells and muscles is another and recycling neurotransmitters is another one. However, GPs tend to be fixated on the first and think that this is what causes all the symptoms so if anaemia isn't present then no problem.

PA is just one possible absorption problem that leads to a B12 deficiency. You need treatment with injections if you have a B12 absorption problem whatever that problem is. The fact that you have a diet that should include lots of B12 implies that you have an absorption problem and this is what should lead to identifying the correct treatment - shots. Testing for PA may or may not show that you have PA, but it won't show conclusively that it you don't - the test is prone to give false negatives.

Serum B12 as a test shows the levels in your blood but doesn't provide any information about what is actually happening at the cell level - homocysteine and MMA tests which look at waste products that build up if there isn't enough B12 available at the cell level may help to clarify the situation. What really counts with B12 deficiency is the symptoms.

You may find it useful to pass this alert from UKNEQAS about the importance of clinical evaluation to your doctor to get them to stop focusing on the blood tests and the lack of anaemia



Great thank u, I'm waiting for the IF result and a full blood count to come back. So the chances are PA won't show up yet but could do in 3 months time. As mine had gone from 175 to 162 in a wk she implied " it's because we are different at different times" I'm sure that's true, but like u say they just home in on results and ranges. She suggested holland and Barrett but I don't think that's going to get me to the 800 I need to be for my thyroid.! And to safely try for a baby, I've written a letter so I'll also take what u suggested. Plus guidelines . We will see, thank You again for explaining 🙌 :)

1 like

Hi Ndobins you don't actually say whether you have any of the symptoms associated with Vitamin B12 Deficiency.

If the "162" you quote is your B12 level then you are definitely low regardless of whether the test result say "normal". Do you know the ranges the lab used for the test?

I am not a medically trained person but if as you say you want to "safely try for a baby" then you need to have your Folate level tested as this is not only good for pregnancy but it is also essential to process the B12.

I wish you well for the future


Hi Clive

Range is 150-900

Yes folate fine.

I'm dizzy upon standing low mood, extremely tired and very foggy and forgetful .

I've told them all this and that we want to try but it falls on deaf ears, waiting for latest bloods :)

1 like

to be clear - you do have symptoms of B12 deficiency. The symptoms of PA are the symptoms of the B12 deficiency it produces

You are not showing signs of macrocytosis - probably - but this is just one of many symptoms and waiting until it appears if neurological symptoms have presented first - could result in permanent damage - refer to BCSH guidelines - link in pinned posts


As Gambit62 says "you do have symptoms of B12 deficiency" and your level is only 12 above the bottom.

List your symptoms and present them to your doctor as it is so easy to forget vital things when face to face. Also, can you take someone with you who can vouch for the symptoms as your doctor is less likely to dismiss your claims in front of a witness.


Ideally you should be receiving more frequent injections as the BNF guidelines say below of treatment with Hydroxocobalamin:-

By intramuscular injection, pernicious anaemia and other macrocytic anaemias without neurological involvement, initially 1 mg 3 times a week for 2 weeks then 1 mg every 3 months

Pernicious anaemia and other macrocytic anaemias with neurological involvement, initially 1 mg on alternate days until no further improvement, then 1 mg every 2 months.


Reminds me of Achilles and the tortoise. In a sort of inverse way.

If your FBC couldn't change in 6 months, let them explain, how could it change in six months and a day? If not in six months and a day, how so in six months and two days? Six months and three days? ... Twelve months? Twelve months and a day?

And if it could change significantly in six months and a day, if the doctor caught it more quickly, it could be treated so that it doesn't have to change so much - with the obvious consequences for health.


You may also like...