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Pernicious Anaemia Society
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Comparison of active and ordinary serum vitamin B12 test results

Hi, I've come from the Thyroid UK community: one of the administrators suggested I post a query about vitamin B12 testing here and I would be very grateful for any comments. I recently had an active vit B12 test (Blue Horizon) at the same time as an ordinary one (included in a test for various other things as well). I have had palpitation problems since early December and have been on T3 only (successfully) for the past seven years. Trying to work out what is causing the palps (I'm under cardiac investigation), I've been gluten free for about four months and am not supplementing vit B12, ferritin or folate.

I had a serum vit B12 test in May 2015 which was 404ng/L (160 - 900)

The recent active B12 test was 120pmol/L (25.1 - 165) [equiv to 162.6ng/L]

The recent serum B12 test was 383pmol/L (250 - 750) [equiv to 519ng/L]

So my vit B12 levels have definitely improved, as have ferritin (131ug/L) and folate (7.93ug/L). My question is, as my active result is good but my serum level not great should I be supplementing vit B12?

4 Replies

It can't hurt to give it a go. Quite a few people seem to have symptoms that disappear when they take B12, even with high serum levels. All the active B12 test tells you is that you've got lots of B12 in the form that can enter cells. It's still possible that something else is stopping it from working.

So, yes, try taking B12 as a sublingual spray or tablet, or as a skin patch, and see if it improves things. I'd start at 1000 ug every other day.

You can't take too much B12 so it's perfectly safe.


Thanks fbirder for your clear, sensible advice. I think I should supplement my folate levels as well.


Make sure your Folate level is OK before supplementing B12 glamrocks4girls as B9 is needed to help process the B12.


Thanks clivealive, will do.


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