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Medical paper re: low in-range B12 levels

Hi, can anyone point me in the direction of a peer-reviewed paper that deals with low B12 levels in range and the need to supplement if the patient is symptomatic.

My 87-year-old father has recently been tested twice for both B12 and Folate, with the following results:

8 August 2017

B12 380 (223-1132)

Folate 4.1 (3.9-20)

31 October 2017

B12 450

Folate 3.3

So, the B12 has slightly increased but the folate has decreased and is now below range (despite my Dad eating more folate-rich foods of late).

It's a bit of a mystery. I accompanied by Dad to his appointment with his GP in late July and the doctor was going to trial him on B12 but has since reneged on that. He does, however, want his folate testing again in three weeks.

He hasn't had any thyroid testing (the last time being 2014 when it was low in range so ideal) and his ferritin levels are very good.

I would like to go again with my Dad when he sees the GP and go armed with good evidence that Dad should be given a B12 trial. I really don't know why it's so difficult!

Many thanks

4 Replies

This is a past post from with a Professor informing us about high homocysteine levels causing the brain to shrink and develop alzeimers. He states that taking B12 helps reduce homocysteine levels. As I also have P.A. I was interested in this as many who have P.A. are restricted to quarterly injections alone.


Many people who actually have other serious problems even doctors are unaware of as shown by the following link as the man in the link is a doctor and no-one at the hospital ever thought of a B12 deficency.

Supplementing with B12 methylcobalamin sublingual tablets wont harm anyone. There's so much ignorance You can also ask on the Pernicious Anaemia forum too.


1 like

suggest you look through the pinned posts on the PAS forum


if you are UK based then the document you want to point your GP at is the BCSH guidelines on the diagnosis of cobalamin and folate deficiencies which they can access through the BNF but can also be accessed here


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Thank you for this - I've quickly checked the BCSH guidelines, but these appear to toe the party line as they cite 200 ng/L as the lower value. I'm sure I've seen reference to a recent paper which suggests that this should be raised to 400 ng/L (or even higher). I'll have a look at the PA posts you recommend.


ann, blood tests are only diagnostic tools - they need interpretation in a context that that includes symptoms. It is unfortunate that most GPs seem to have lost sight of this very important fact.

the important thing is that the paper highlights that symptoms are important in diagnosing and also highlights the limitations of the test and the importance of symptoms (though has to be noted that these also overlap with thyroid problems and a number of other conditions)/

The normal range is a statistically determined range but this range will result in missing 25% of people who are B12 deficient (and also picking up 5% who aren't) so serum b12 should not be taken as a single indicator and symptoms are important. It also highlights that 25% of people do not have macrocytosis (enlarged and rounder red blood cells) when they first present with B12 deficiency.

There is some discussion in the US about the use of 'reference' ranges rather than normal ranges - which includes a proposal that reference range should be raised - think this mainly comes from Sally Pachalok and those who are involved with the B12 Awareness - the charity she founded in the US. Personally I would prefer it if labs actually did more to highlight that the test cannot be used as absolute indicators and include a number of ranges indicating subsequent action if the patient is showing a number of symptoms - part of which is actually covered in the BCSH guidelines.

serum B12 is a useul test for diagnosing absorption problems - something that is quite likely to develop if you have an auto-immune thyroid condition. However, this is only part of what can cause a B12 deficiency - there is even a condition called functional B12 deficiency which arises when serum B12 is high but not enough B12 is actually getting through to cells - one cause of this is another autoimmune condition.

Please, if you want to pursue this further, take a look at the PAS forum


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