Measuring B12 levels

[foxrabbit]

Hi everyone,

I don't have PA, but I do have a thyroid condition which usually comes alongside low B12 levels. When I was initially diagnosed with the condition my B12 level wasn't ridiculously low, I think it was around 450 with a range of around 180-900, but as I had some numbness in my fingers I started supplementing with high strength sublingual methylcobalamin just in case. Ever since this, when I've had my levels done on the NHS it shows my level to be >2000 on the same range but some knowledgeable members of the thyroid forum pointed out that when supplementing it gives false results.

So, my question is, how do I find out my true levels? I ask as my numbness is back despite my levels being high!

Many thanks

[Gambit62 Administrator]

the only way of getting a base line would be to stop supplementing for 3-6 months - possibly even longer.

450 is actually quite a good result - 500 has been quoted a lot on TUK as level needed but I'm not aware of any evidence that thyroid necessarily requires this level. Depending on the units involved in the test (ng/L or pmol/L) your result might well be above the level quoted. 500ng/L is the level up to which there are reported cases of neurological damage and is the level that would be used in Japan to treat someone who was symptomatic.

evaluating symptoms where there is also thyroid problems is extremely difficult because of the overlap in symptoms from the two conditions.

Has taking the supplement actually resolved the symptoms you mentioned.

The fact that your levels have risen to over 2000 with the dose you are taking would suggest that you don't actually have an absorption problem (getting B12 from food into blood)

Some people respond to high levels in serum by shutting down the mechanism that allows B12 to pass from blood to cells. This will leave you deficient at the cell level. Unfortunately this reaction also results in B12 being retained longer in blood and seems to affect the normal removal from your body so waiting for levels to fall could take a long time. An effective way of treating the condition is to raise levels even higher. This may not be what is happening with you - and your symptoms may actually not be down to B12. Folate deficiency has quick onset of symptoms and they are very similar to the symptoms of B12 deficiency - there are also a whole raft of things that can cause neurological symptoms.

If you have a functional B12 deficiency it may be possible to detect it by looking for effects - MMA and homocysteine levels will be raised if you are B12 deficient - but can also be raised by other things.

[foxrabbit in reply to Gambit62]

Hi Gambit62, thank you for your reply and the information.

I never knew if the B12 caused my finger numbness as I started treatment for my thyroid at the same time as starting B12 supplements so I couldn't tell which one cleared it up. I started the high strength supplements again when my symptoms returned but after two weeks I saw no improvement. I'm not sure how long it would take to see any improvement though.

The supplements I take are sublingual so should avoid the absorption in the stomach issue.

I'd read before in a well known B12 book that there are no side effects from overdosing on B12, so your information on high levels in serum and not passing into cells is concerning! I will have had >2000 for a couple of years now due to taking the supplements as a precaution thinking it wouldn't harm me! I think I will read into this some more.

Thanks again

[Gambit62 Administrator in reply to foxrabbit]

Actually most of the sublinguals absorption seems to be via the gut and very little through membranes in the mouth based on comparisons of absorption from the two methods.

If you haven't had symptoms for a while whilst your levels were over 2000 but they have recently returned then that would imply that the reaction isn't a factor in your case as it would have kicked in when your levels got high - which would leave the main problem with the amount you are supplementing as being financial as without an absorption problem the sort of dose in a multivitamin would be more than adequate and a lot less expensive.

It sounds as if the symptoms you mention probably aren't related to B12 - MMA test would help to rule it out. Think you should be looking into other possibilities and may be trying for a referal to a neurologist.