Thyroid UK
82,777 members97,801 posts

Vitamin B12 testing: completely pointless??

I recently had my active vitamin B12 tested by Blue Horizon and the results showed it was within the normal range (76 pmol/L). I've read elsewhere on this site that there are recommendations to have an MMA test, if the B12 result is less than 70. I haven't come the MMA test before, so had a little look around on the internet.........even though my result is NOT less than 70, it is quite close and I wanted to see if I would benefit from an MMA test.

Apparently, the MMA test is the ONLY test than can tell if you are B12 deficient or not. Methlymalonic acid (or methylmalonate; MMA) is a waste product that builds up in the blood if B12 is not available. I read that you can have low, normal or high levels of B12 and STILL be deficient, and the MMA test is the only way to find out. Presumably it's a more accurate indicator of B12 deficiency because it's showing whether the metabolic need for B12 is being met by the levels of B12 in the blood..... or something. Not entirely sure, to be honest.

So, I am now thinking that my paying £64 for the B12 test was a waste of money and I should have just gone straight for the MMA test (£324 for blood test or £139 for urine test, both with Medichecks - yet more money!)

I wanted to raise this, in case it helps others when deciding what tests they need. I'd also be interested to hear if anyone knows whether the above is totally correct or not!


18 Replies

Chooselife, the PAS advice was to have MMA if Active B12 is under 70. Your result is 76 and is above the threshold for doubt so there doesn't appear to be any necessity to pay £324 for the MMA test.


Thanks for responding, Clutter. But if what I've read is correct - that a normal B12 doesn't necessarily mean that you don't have a deficiency - then it would imply that MMA testing is more accurate than B12 testing?

Here's where I got this from (not sure of the sciencitific validity of it though):


But were they talking about the normal B12 blood test, or the active B12 blood test? The active test is supposed to be more acurate. But I agree, the normal one only tells you what's in the blood, and not in the cellls, so you could still be deficient even if your result is high.


Hmm, yes I see what you mean. I've just skim-read the article (that I provided the link for) again and it doesn't specify "active". The test I had was for active B12, so I agree that this would be more accurate than just the normal B12 test.

I'm kinda wondering whether the MMA test might be even more accurate than the active B12 test, because I think it's telling you what your cells are actually using....... Could there be a scenario where you have plenty of active B12 circulating round your body in the blood, but the level getting into the cells is not sufficient?


As I understand this article, it wouldn't.


You can pay a lot less than £324 for an MMA test. I just checked one of Blue Horizon's websites - they have several and I haven't checked them all so it may be possible to get it cheaper - and they charge £126.15.

And for that price you can also get a free blood test thrown in (there is a list to choose from).


Thanks, humanbean. I should have added that I need to have an at-home test (or at least not have to travel more than a few miles). I couldn't find MMA testing on the Blue Horizon fingerprick website and I think their nearest blood-drawing place for me is over an hour and a half away.

But the Medichecks urine test is only £139 and I've just read on the Pernicious Anaemia Society forum that urine is more accurate.....maybe I'll go for that.


I've pernicious anaemia 16 years. I was half dead on the 3 Monthly nhs injections of b12. I asked for mma tests over and over as I felt so ill. No joy. Felt like a slow death. So I inject myself weekly with methylcobalamin subcutaneous for last 7 years and I am well , swimming in b12.

I've given up on GPS and begging for tests and go by how I feel and treat myself as well as I can.

less anxiety.

Take care


Thanks for responding, jobeth. Glad to hear that you're better now :)

Is very interesting to hear that you've been able to find the level of supplementation that makes you feel well! And that you did this without the MMA test. Just goes to show that you can experiment yourself and find what works for you (and not just what the doctor thinks should work for you!!).


Yikes! My local Lab in Dunedin NZ, considers any serum value under 172 to be of concern. Mine was 85 and I was immediately put onto B12 injections!


Test being discussed is active B12 not standard serum B12 and has a very different range.


Thanks for responding, mongolia1 and helvella.


My serum b12 test was 'off the scale' over 2000 and I was b12 deficient with PA and no parietal cells left (shown with stomach biopsy etc). My GP said I'd never get PA. Good job I didn't listen to him.

The serum b12 test is just not accurate as it is active b12 (holotranscobalamin) that counts.

Its how you feel after cobalamin that will make you aware of how ill you are (well that's what I found). Whether methyl, hydroxy or adenosyl-whatever works for you (I wouldn't do cyanocobalamin but that's my choice) .

If I had waited for a low serum count to appear, I would have died like my grandmother with PA whilst the doctors all screwed their faces up in confusion and disbelief as to why she died with PA if her serum b12 was so high!


Blimey....... I am shocked by this and so sorry about your grandmother :( .

After researching earlier on this forum, I had the active B12 test, luckily. But shocking that doctors are not aware of the inaccuracy of the normal serum B12 test.....Yes, a darn good job you didn't listen to your GP!


I know, it is awful...

However these days I find that nothing shocks me anymore....I just feel saddened really.

I nursed my grandmother through PA until her death and believe me it is not an end I would choose for anyone.

I thought that by now the medical profession would have the answer...but, ironically it seems that it is us patients who have the answer, but no one will listen....

1 like

If you cannot travel you would be best going for urinary MMA as it is said to be better in 'Could it be B12?' Book. Active B12 is more accurate than serum B12 but no test is 100%. The cost of treatment is very low so many people don't pursue private testing. I asked for MMA and homocysteine but was refused. I had a low serum B12 which my GP was not going to treat but eventually (lots of persuasion using guidelines) did. I feel an awful lot better than I did a year ago.

I stumbled here from PAS forum- try posting there as there are some very experienced people. A recent BMJ article suggests if in doubt to treat rather than relying on tests.

Good luck


Could somebody please advise me about the value ranges for The Active B12 test, and MMA - and what numbers for both that would show a b12 deficiency

Also I have SIBO - Small Intestinal Bacterial Overgrowth - which falsely elvates the test result of a serum b12 test - would this also affect the active b12 and MMA test?

Thanks in advance



I urge you to post that question over on the Pernicious Anaemia Society forum

We have people who know quite a bit about B12, indeed we have many members in common, but it is often better to post B12 questions over there.


You may also like...