Pernicious Anaemia Society
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Vitamin B12 Deficient, low ferritin levels but hb ok

Hello everyone!

I’m so glad I have found this page.

I’m wondering if anyone can help me- in June 2017 I had a funny turn in work and had some blood tests (felt faint, drained and generally unwell) my b12 came back as 150 and ferritin 14 but hb was fine (can’t remember exact number) vitamin d was 45

I began replacement therapy of 6 vit b injections, and Ferrous fumerate 210mg TDS. And a follow up blood test after treatment, b12 came back as >2000 and ferritin 20.

I was referred to Gastro and underwent an OGD which was NAD. Was tested for coeliac-nad and PA which was NAD. I have also had an MRI of the bowel and that was NAD. Advised by gastro that it seems likely to be caused by diet (even tho I eat very well) and to continue with replacement therapy for 2 years then to stop and have levels checked again. Ferritin caused by heavy periods? (Although this is something I’ve always had and they’re not always heavy)

Since then I have been in contact with my Gp fairly often with similar symptoms, I seem to last for 10 weeks then I start to get neuro symptoms again, such as tingling in fingers and toes and brain fog!! I also feel faint quite often.

I have just had more bloods taken on Thursday to check levels but still awaiting results. My last blood test 5 months ago b12 was 300 and ferritin 30.

Does anyone know what could be going on? I’m at a loss and I don’t think my Gp understands how awful it makes you feel :( my consultant didn’t seem interested either.

Thank you in advance!

5 Replies

The test for PA produces false negatives about 40-60% of the time depending on the test method so a negative is a long way from proving that you don't have PA as the cause of B12 deficiency.

Would be useful to know where you are based. In the UK the standards should be to assume, in the absence of another cause that the reason is PA - and standards include IFAB negative PA as a result.

lack of iron produces microcytic anaemia in which your red blood cells are smaller than normal. B12 and folate deficiency produce macrocytic anaemia in which your red blood cells are larger and rounder than normal - which could be why the haemoglobin seemed to be okay.

Very unlikely that the cause is dietary if you eat meat/fish/dairy/egg.

PA can also affect the absorption of minerals beyond B12 - including iron and folate.

In the UK treatment for B12 absorption problems in the presence of neurological symptoms is bi-monthly maintenance doses, not three monthly (though many find that even 2 months is too long).

Serum B12 is not a test that can be used to monitor and treat a B12 absorption problem - it just tells you what is happening in the blood (and the dominant factor there is the amount you had injected into your blood). It doesn't tell you whether the B12 is getting through to your cells or if it is actually being used in your cells.

To be honest 300 is, on average, for a patient who is on B12 shots, quite a low result - so not surprising that you are starting to re-experience symptoms.

Unfortunately you seem to be surrounded by a bunch of medics who don't really have much knowledge or interest of B12 - many think it is all about anaemia but it's a lot more.

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Dear Gambit,

Thank you so much for your reply, that was very useful! My latest ferritin came back today as 50, seems to be taking a while, hopefully if I can get this to 100 I may feel better.

Forgot to mention that I had a BT for the ‘active’ b12- that came back at 256 which the doctor reported as ‘good’

I will request to have b12 every 8 weeks although it is a nightmare trying to get an appointment, I was thinking of buying my own b12 and having a colleague administrate (I’m a nurse)

Yes I really feel as if my medical team aren’t interested/lack the knowledge, what would you suggest I do next? :)

I’m based in Plymouth, Devon

Thank you!

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Hi Sophie, going through exactly the same low b12 (173) and ferritin (10)

I have had neuro symptoms too, pins and needles, burning and muscles hurt/ feel weak in arms and legs.

Had MRI of brain which was fine and neurological checks of weakness and reflexes- again all fine.

Been on iron for a few weeks but still feel shattered and achey.

I think persevere with drs- I am going back and asking to be referred to a haematologist as I am so worried b12 and iron hasn't helped.


Hi F!

I sympathise with you, it’s really horrible :( I’m going to speak with my Gp this week and relay the information I have learnt from here, I was hoping for a haematology ref as well. Hopefully we will get there in the end x


Good luck Sophie.

Honestly understand how your feeling.

Fingers crossed we get some more answers soon

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