Pernicious Anaemia Society

Avtive Vitamin B12 test

Can anyone tell me how long before the test must you stop vitamin B supplement? I am suffering nerve damage. Burning mouth, lips, tongue, fingers on fire. night time really bad and pain wakes me up at about 3am spreads up legs and down arms. So I in panic started dosing with B vits. Had taken B vits before to raise my B12 level from 191 a few years ago and so with supplementation over the years have got my total B12 blood test level up to 550 6 months ago - stopped supplements and recent test shows 400. Then suddenly hit with this nerve damage indication over the last 10 days.

I am going to have to have a private active B12 test as GP says my levels are fine.

Even tho current NICE guidelines are treat if have symptoms irrespective of serum levels. I asked for a B12 injection just to see if symptoms then start to subside. According to the PAS society B12 is harmless and costs 56p. I hope the active test will highlight if symptoms are B12 deficiency. If it is not B12 I suppose it will ten be autoimmune attack on my myelin? I have high ferritin but bordering on anaemia with v low transferrin saturation at 18% and my TSH has risen to 3 so wondering if thyroid/iron symptoms - all connected?

But first I need an active B12 test and want it to be relevant, not be skewed by recent supplementation. Any advice would be really appreciated. I have managed to get a GP appointment this evening and wonder whether I should print out te guidelines and take with me? Any advice, I would really appreciate :)

4 Replies

I would seek advice from the Testing Clinic. I was told by Martyn Hooper - Chairman of the PAS - that B12 can hang around a long time - even more than 6 months in some cases. The Active B12 Test still does not show you what is in the cells - only the B12 that can travel from the blood to the cells so .....

If you have symptoms of PN go to the PAS website - check out your symptoms against their list and then go back to your Doc. If you have neurological symptoms then you should be treated - irrespective of the test result. They will also help you to have a dialogue with your GP.

The letter to your Doc is included in the above link along with a host of information ....

The MMA and Homocysteine test will show more. Homocysteine is often high when B12 is low.

Take the Guidelines to your GP :-)

Apologies if I have written things you already know - maybe it will help others ....


No, thank you so much Marz. Thanks for the link, I will print off and take with me.

I had read a while ago that Homocysteine was indicative of activity of B12. So I have had my homocysteine serum test measured at GP's and my results are

Please note I have supplemented B12 and then later B vitamin complex on and off for years from when Serum B12 was 191

Most recent


Serum Folate 10.7ug/L

Serum B12 474ng/L

Plasma Homocysteine 8.2 umol/L


Serum Folate 11.3ug/L

Serum B12 551 ng/L

Plasma Homocysteine 9.7 umol/L


Serum Folate 12.2ug/L

Serum B12 367 ng/L


Serum Folate 18.9ug/L

Serum B12 294ng/L

Plasma Homocysteine 8umol/L


Serum Folate 13.9

Serum B12 191ng/L (Report marked as normal lab range 191-663)

I had believed Homocysteine should be at 7

Any thoughts would help


I have read that Homocysteine is regarded to be high when into double figures and good at around 5/6. Good B complex with the B12 should soon sort that out for you. Not many Docs test for Hcy - so you were lucky !

The link above is a website that is far too big to print off - so do have a good read and decide what is needed for your GP. Have you looked at the Pinned Posts on this Forum - if you are on a PC - they are to the right of this thread. On a phone you will to scroll down to have a read.

Ranges for Folate do vary so what is yours - difficult to comment without the range. Again I have read that halfway through the range is good. B12 and Folate work together in the body ...

There are many causes of low B12 - so best to read up on PA and request the relevant testing from your GP.

Raised Ferritin can sometimes indicate inflammation somewhere in the body.

Hope all goes well ....

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Link about active b12 test...see 4th question.

Has your GP read a copy of the BSH Cobalamin and Folate Guidelines?

click on box that says "Diagnosis of B12 and Folate Deficiency" should be on page 3 or put "cobalamin and folate guidelines" in search box.

link to flowchart from BSH Cobalamin guidelines below

My understanding of the flowchart in the BSH cobalamin guidelines (I'm not a medic) is that someone who

1) has low B12 or is symptomatic for B12 deficiency with an in range B12 result

2) has had all causes of b12 deficiency (eg diet) other than PA excluded

3) has responded to B12 injections (eg symptoms have improved)

should be diagnosed with PA

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