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Pernicious Anaemia Society
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High Active B12 - what does it mean please? What shall I do next?

These are my latest results which I posted on thyroid forum but was advised this forum would know more about the B12 question. Thanks :)

I'm not diagnosed and have no prescription medicine. I have lots of hypothyroid symptoms which have actually got worse if anything but maybe it is all in my head/depression worsening?

my vits have 6mcg B12 and medichecks doctor who reviewed my results online said to stop taking them but if having an active b12 higher than the reference range isn't bad then I would like to continue taking them.

They seem to have helped my iron and they don't upset my stomach so I'm reluctant to change.

It's hard to find information on active b12 and what an above reference range means in terms of my health etc

active b12 is above range. What does this mean please?

Active B12 213 (range 25-165)

serum vit b12 636 (200-960) (in sept)

red blood cell 4.43 [3.5-5.5]

haemoglobin conc 135 [115-165]

haematocrit 0.41 [0.37-0.47]

mcv 92.3 [78-100]

mch 30.5 [27-32]

eosinppil 0.03 [0.04-0.4] below range

What's optimum folate? It looks like I'm ok but low in range?

I take 50mcg vit D a day and multivitamins for breastfeeding.

Tsh 2.03 (0.27 -4.2) (3.41 previously in October)

Free t4 14.1 (12-22) (12 prev)

Free t3 5.17 (3.1-6.8) (4.67 prev)

Reverse t3 16 (10-24)

Reverse t3 ratio 21 (15-75)

Thyroglobulin antibody <10 (0-115) (prev 12.9)

Thyroid peroxide antibodies 12.9 (0-34) (15.8 prev)

Folate 9.46 (2.91-50)

Vit D 49.4 (50-200) (prev 30ish)

Ferritin 58.9 (13 -150) (prev 17ish)

Thanks everyone

10 Replies

Hi tiredBFmum fortunately you cannot "overdose" on vitamin B12 as any excess to requirement is excreted via your urine so although your levels are "fine" as long as you are feeling a benefit I would suggest you continue doing as you are.

Your Folate level is a little on the low side and as long as you are supplementing with the B12 it may pay to increase your Folate by eating plenty of leafy green vegetables, sprouts, broccoli, spinach, peas, beans etc. Many breakfast cereals now have folic acid added. Alternatively you can buy folic acid tablets cheaply over the counter at any chemist or supermarket. Have a word with the pharmacist to advise on what strength to buy.

Are you taking anything for your low Vitamin D?

I am not a medically trained person so cannot comment on all the test results you posted but I've had Pernicious Anaemia (a form of B12 deficiency) for 46 years, am permanently on B12, folic acid and iron supplements and I wish you well.

1 like

clivealive thanks for your reply

am taking vit D (around 50mcg a day) thanks. I will then reduce this to around 20mcg when my levels are better.

good time of year to get hold of fresh sprouts and i love spinach so that should help my folate.

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Just to give you perspective on D3:

I'm on 1600 mcg (2x800) daily prescribed by Endo about 5 years ago. Blue soft gel tablets filled with oily liquid for best absorption.

My d3 levels are now 110.

From what I've heard 1600 mcg is maintenance dose.

If you want to increase your d3 levels you need to go more than just 50.



Are you mixing up your mcg with IU for the D3?

25mcg D3 = 1000iu

Prescription D3 is usually 800iu for maintenance which is 20mcg.

So I don't think you will be prescribed 1600mcg :)


Yes, yes you're right Susie.

Silly me.

Apologies for feeding you baloneys! 😱


Easily done, especially with out foggy hypo brains :)


All my family suffers from pernicious anaemia and I used to give them injections but we get excellent effect from B12 5000iu sublingual tablets. Our doctor is not worried and there is no known toxic range. See this article: candobetter.net/node/4463 It has links to two excellent films on the subject, plus cites US guidelines for dosage. Mind you, I have never had my 'active' B12 done, but everyone in the family is around 1400 when the 'therapeutic range' is something like between 150-350.


Active B12 measures the amount of B12 in your blood that is bound to a protein - TC2 - that allows the B12 to get from your blood to your cells where it is used. In general this will be 20% of the B12 in your blood.

The level you have indicates that you probably don't have an absorption problem. However, as you aren't supplement with significantly high levels of B12 (6mcg is between 1 and 3 x RDA) the fact that it is raised above the normal level could be indicative that there is something else going wrong in the full process of metabolising B12.

Basically there are three steps in metabolising B12 (that's very simplified) - getting it from your food and into your blood, getting it from your blood into you cells and then actually using it for a number of processes in your cells. Things can go wrong at any of these points.

The most common place for something to go wrong is the first step and serum B12 and active B12 can be useful in identifying this as both will be low. However, they don't tell you an awful lot about what is happening in the other two steps.

I'm not an expert but as I understand it looking at the ratio of active B12 to serum B12 can indicate of a problem in step 2 - if active B12 is high but serum B12 isn't then that would indicate that there is something that is stopping B12 getting into your cells.

There are a couple of tests that can help to clarify if something is going wrong in the third step - using the B12 in your cells. These look at waste products (MMA and homocysteine) that build up if your cells doesn't have enough B12 to recycle them into useful building blocks. However, they can also be raised by other things - including liver and kidney function - in the case of MMA.

There are a few things that can cause the levels of B12 in your blood to rise aside from supplementation - some people naturally have higher levels than normal and are perfectly fine but for other raised levels in their blood cause a reaction that stops the B12 getting through to their cells leading to a functional B12 deficiency. Lots of B12 in your blood but none at the cell level.

Your GP is highly unlikely to be aware of much if any of the above - generally they have an awareness that something can go wrong at step 1 but nothing beyond that.

This is a link to the BCSH guidelines on diagnosis and treatment of cobalamin and folate disorders.


your GP can access these through the BNF (assuming you are UK based). It gives information on the various tests that can be done in relation to B12 and some guidance on how to interpret them.

This is also a link to an article on functional B12 deficiency


I'm sorry that I can't give you any exact answers but perhaps this information will help you find a direction and a way of working with your GP to get to the bottom of things.

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Gambit62 thanks that's really interesting and informative.

It sucks that we have to research and try to understand these things because patients have to be their own advocates.

I am so tired of being tired and I can't remember the last time I felt "well"

I daren't go to GP until I understand things a bit better for myself so I can ask the right questions and defend from the eternal "you are just depressed"! Because depressed people never have any physical health problems?!?

I only found out about the vit D deficiency after expending my very limited energy persuading them to test me.

If I blindly listened to the GP I would just be on antidepressants getting more and more deficient in vitamin D without supplements over the winter.


do you have a relative or a friend that could go to see the GP with you? particularly if you are struggling with understanding things they might be able to help you out ... and sorting out a script for yourself can also help


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