Pernicious Anaemia Society
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Active B12 results


Following on from previous posts, I got my active B12 results back today.

Talk about paradoxical!

I was expecting a low measure, as currently have symptoms and blood anomalies that might suggest deficiency and consultant said in December that I have megoblastic anaemia.

Results are>256.0

Normal range is 25.1 - 165.0

So this says I am well above top end of normal.

I have no idea what this means - it makes no sense.

I have been taking a methylcobalin sublingual on and off in the two weeks preceding test, so this may have skewed it. But serum levels were 301 when last tested, so nothing is adding up.

Supplementation aside, does anyone know what this reading suggests?

10 Replies

I would probably have stopped taking any supplements for about 2 weeks before having that test so perhaps this may have skewed it. Have you had your folate and iron measured? It could be that you have another deficiency which is causing your symptoms as well.

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Unfortunately the reading suggests that your supplementing has skewed the results.


Also thyroid testing would be good , as in previous post other topic.


I don't know what her symptoms were - but if she had megaloblastic anaemia then that suggests B12 deficiency.

We could, of course, throw the spanner into the works and mention Carmel's work on people who have high b12 levels and b12 deficiency....


She had half her thyroid gland removed, no further testing after..this was my response on the same question about her high active B12 result, it seems lots in all these muddled up posts, pasted below:

Hi Suki,

It does look like you are B12 replete in tissue and in serum, I personally would start thinking your symptoms are not specifically related to possibly having a B12 def. Re:"I have been taking a methylcobalin sublingual on and off in the two weeks preceding test, so this may have skewed ", yes the supplementing will have skewered the results (you need at least 4 months without for it to be a natural result say). High MCV can also be caused by a folate def and or thyroid problems besides other not nice issues as in my previous post. I do think retesting thyroid once half the gland has been removed seems the most logical thing to do in your case, but I am no thyroid expert!

Kind regards,



Re-testing the thyroid would make sense but it still depends on what her symptoms are.

Just because she is testing normal for B12 now doesn't mean she didn't suffer permanent damage when she was deficient - and she had megaloblastic so would have been deficient then.

What I am surprised about is that the test was done without checking she had abstained from B12 in the first place?

Again the goal posts keep changing with how long you should abstain but she could have had a lozenge an hour or two before the blood test.


More info in her other posts, see:


Thanks Marre

Always there - that MCH - nudging into the high end.

It bugs me.

If she had megaloblastic then the cause is limited. I didn't read the whole of the thread... though so I can't comment further.

Gotta work.


Hi Poppet11

Thanks and to all who have responded.

I could easily have skewed the results and am taking that up with the lab as they didn't say anything about abstaining. New to this and realise now that is crucial.

I can't find any info on Carmels work - would you be able to let me have a reference?

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I would take it up with the lab. Most tests you have done privately, including the MCV test you can send off for, state that supplementing will skew the results.

With regard to Carmel's work - I haven't got the research to hand - but don't sweat it. It only confuses things more.

The problem with all these tests are that they are interpreted as if they are accurate. I queried this with Hunt in the BMJ about the levels of the serum B12 being set too low because they were based on B12 deficiency being a blood condition and reversing that condition - that part of the illness is reversed very, very, easily.

She said they were using different tests now. Which they are. But they are still calibrated on the old 'reverse the bloods' figures.

I then see, a couple of months later, work done by Carmel proving that the calibrations are set too low!

Now if the serum B12 is set at levels which only enable it to say when a blood condition may be occuring and when that condition may be treated - and it is wrong - how do we know any of the other tests were set correctly?

Bottom line is they have all, for decades, been assuming B12 deficiency arises from anaemia. It doesn't. Which is why you have a situation in Japan where they realised the error and set the levels at when spinal fluid has DNA changes - rather than the rest of them who are hanging around waiting for blood changes which might never happen - and then telling everyone they are well when the levels go into 'their' version of normal.


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