Pernicious Anaemia Society
14,716 members10,466 posts

Active B12 levels


I've been advised that this is the best board to seek help interpreting some B12 lab results. I understand that this doesn't constitute medical advice, I would simply really appreciating hearing others' experiences.

My newest Active B12 lab results are 110pmol/L within the range of 25.1-165.0pmol/L.

My previous result from my GP was 575ng/L within the range of 200-700ng/L


I'm not sure how to interpret these two readings; there seems to be 2 different measurement systems. Can they be directly compared, and if so, is there a noticeable difference in the levels?

Thank you for you time

14 Replies

The first test is active B12 which looks at just the forms of B12 that are used at the cell level.

The second test is B12 serum test which looks at all the B12 in your blood

ie they are different tests

In theory the first is a more accurate measure of your B12 levels because it is looking just at the forms that have been converted so they can be used by cells - and the levels actually look quite good on both.

However, that doesn't necessarily mean there isn't a problem as there are other things tht can go wrong in getting B12 to cells wehre it is needed and the tests say nothing about this.

This is one reason why clinical symptoms need to be assessed - and you can find a check list of symptoms here


However, there is also a huge overlap between symptoms of B12 and those of other conditions - such as thyroid and diabetes and it isn't uncommon for more than one to be going on at the same time.

Also, results can be skewed if you have been supplementing B12

Do you have folate results as well?  Body needs folate to absorb and process B12.

Tests that can help clarify if there is a B12 deficiency are MMA and homocysteine - both of which will be elevated if you don't have enough B12 and/or folate.


Hi Gambit62,

Thanks for the explanation. Prior to the tests I did not supplement B12. My Folate level was 11.7 from the range of 30-200 ug/L. (June 2015) which has been done together with the test for B12 serum level(575ng/L). 

No Folate levels measured during the latest test which was Active B12(110pmol/L).

For the other conditions-such as thyroid and diabetes, latest tests done are shown below;

Glucose level was 5.1 from the range of 3.7-5.6 and test date was last June. 

Thyroid test results which were dated as September '14 are as shown below;

FT3 4.6pmol/L from the range of 3.0-7.0

FT4 16pmol/L from the range of 10-25

TSH 0.49mU/L from the range of 0.35-4.5

Thyroid peroxidase Ab. 2 reference range; normal less than 60 IU/ml

 I am not sure how my levels could be interpreted as to whether to have the MMA and homcysteine tests (not done on NHS) to follow and/or start taking B12 supplements now or do nothing. Trying to figure out all these on my own confuses and overwhelms me.

Many thanks for your time


Hi ABC100 

Welcome to this community.

You say "My Folate level was 11.7 from the range of 30-200 ug/L. (June 2015" This looks low and as Gambit62 says above the "Body needs folate to absorb and process B12." so maybe there's a clue there.

I am not a medically qualified person so whereas I can't give answers I can ask questions

You don't indicate why you are having all these tests carried out or what your symptoms are:

What is your diet like? If you "Google" Folate rich foods you'l find lots of advice - e.g. below.

"Folate is found naturally in a wide variety of foods, including vegetables (especially dark green leafy vegetables), fruits and fruit juices, nuts, beans, peas, dairy products, poultry and meat, eggs, seafood, and grains  Spinach, liver, yeast, asparagus, and Brussels sprouts are among the foods with the highest levels of folate."

As I understand it you need to elevate your folate levels BEFORE supplementing b12 but hopefully someone else more knowledgeable than I will explain this.

I wish you well


Clivealive is right - your folate levels are low - and need to be addressed if you are going to be able to use B12.


Hi Gambit62,

I just realised I made a mistake on normal range of Folate levels. Correct levels for the range is 3-20 microgram per litre. Thank you very much for helping me to understand.

with my best wishes


The range did look a bit strange - level of folate is okay though if you are going to supplement B12 it's best to have it in the upper half of the range so looking at diet would be a good thing as best form of folate is definitely from diet


Hi ABC100 - I think the result you mentioned first could well have been Ferritin - stored iron - in which case that needs to be much higher in the range - around halfway.  Are you treating this very low level with some sort of iron supplements ?  Low iron can make you feel very poorly.


Hi clivealive,

Thank you very much for your warm welcome and your reply and many thanks for inadvertently signposting me to my mistake that I have put my Folate levels wrong. They should have been "from the range of 3-20 microgram per liter"

Then my level of 11.7  looks good.

with my thanks and best wishes


While your tsh looks good some people don't feel well unless that is suppressed and the t3/4 is at the top of the range or even slightly elevated. You could check your symptoms on www.thyroid to see if thyroid issues are a possibility. 


Hi- are you on any medication eg thyroxine? I would have said your FT3 is lower than it could be to feel better. Has your ferritin been checked?

MMA and hcy good tests to have. 


Hi Bluedragon,

Thank you for replying to me. I am not on medication apart from vitamin D supplement. My serum ferritin level is 87.1 ug/l from the range of 10.0-250.0 from test dated October 2015. I don't know how to read this in relation to anything else. As for the FT3 level, my GP didn't say anything apart from that they are all within the normal range. On the other hand my symptoms are still real with me and eroding any quality of my life left. Hence here I am trying to understand and help myself within these very helpful communities.

with my best wishes

1 like

...;ooops sorry ABC100 - have just seen this Ferritin result - apologies. 


I would strongly recommend an MMA blood test, and a total homocysteine (if they'll do it). That would give a very good indication as to whether your B12 is doing a proper job, or not.

Another way to tell if your symptoms are due to B12 deficiency is to start taking some form of supplementation and see if your symptoms abate.


Looking through past posts, I notice you have several neurological symptoms that could indicate B12 deficiency, (anxiety, sore mouth, fibromyalgia, etc. and, although testing MMA is more specific for B12 deficiency, there really is no gold standard test.

Also, as you probably already know, autoimmune thyroid problems and PA/B12 def. are often interlinked, with symptoms overlapping and leaky gut/intestinal disease the source. I believe this is at the bottom of all our own family autoimmune/thyroid/B12 issues. I found the following from Dr Tofts' book, 'Understanding Thyroid Disorders', published in associated with the BMA, helpful:

"There is considerable debate about the correct dose of thyroxine. The consensus is that enough thyroxine should be given to ensure that levels of T4 in the blood are at the upper limit of normal or slightly elevated and those of TSH at the lower limit of normal, or in some patients undetectable." 

Re. B12 deficiency, your GP should be treating your neurological symptoms, as defined in the latest BMJ research document and various BCSH, NICE, UKNEQAS guidelines.  

Extract from the book, 'Could it be B12?' By Sally Pacholok & Dr. J Stuart 

"neurological symptoms can occur in isolation, so it is important to consider a diagnosis of B12 deficiency in the presence of neurological symptoms of unknown cause as neurological symptoms may progress and become irreversible."

Here are some helpful sites:

(List of symptoms and templates for writing letters)

“In the event of any discordance between clinical findings of B12 deficiency and a normal B12 laboratory result, then treatment should not be delayed. Clinical findings might include possible pernicious anaemia or neuropathy including subacute combined degeneration of the cord."

Points from the latest Cmim/BMJ Research above with useful summary, if GP won't read full document:

* Vitamin B12 deficiency is a common but serious condition

* Clinical presentation may not be obvious thus leading to complex issues around diagnosis and treatment.

* There is no ideal test to define deficiency and therefore the clinical condition of the patient is of utmost importance." 

* There is evidence that new techniques, such as measurement of holotranscobalamin and methylmalonic acid levels seem useful in more accurately defining deficiency.

***If clinical features suggest deficiency, then it is important to treat patients to avoid neurological impairment even if there may be discordance between test results and clinical features.

FBIrder's summary of BCSH, NICE, etc. guidelines and BMJ research on B12 deficiency:

1 like

You may also like...