Pernicious Anaemia Society

Hope this doesn't sound daft

Does raised serum and active b12 levels after taking b12 suppliments prove you are able to absorb b12 taken sublingualy?

I keep reading that taking b12 skews results but can't really find the relevance in such a remark or any research on it apart from statements by people.

By what process does it skew results as surely it proves the b12 made it to the blood.

I got my b12 up nicely on suppliments but still feel rotten even dare I say it worse than before I started b12. Much worse.

5 Replies

not necessarily - its all rather complex

an absorption problem doesn't necessarily mean no absorption and the sublinguals contain really high doses of B12 ... and there is also a limit to how much B12 your body can actually absorb through the gut.

There is a risk with using high dose sublinguals, particularly if you don't have an absorption problem, that they can raise your B12 levels to the point at which your body reacts by trying to shut down the mechanism that transports them to cells but its not clear how many people respond in this way - just that it is a possibility.

Sorry - as with a lot of B12 there aren't clear answers - too much in terms of genetics and biochemistry ifs.


Hi Steap

I am new to this s forum .. thanks for your post....I am like you my blood test results show good improvement, but I still feel the same, perhaps slightly worse. numb hands every morning etc..? My feet are getting worse!! I was on ppis for stomach until recently. Reduced 3 months ago and stopped 3 weeks ago... I seem to have raised Vit D, Ferritin and Folate ok .... but unsure re B12. I am going to keep taking B12 lozenges but raise amount and retest B12 in 6-8 weeks and if it's higher at least I know something is going in!! Certainly is complex!!!! Hope we can get answers and results soon!! Hugs xxx


Flippin heck talk about a quandary. So taking too much orally can switch off things.

I'm only taking 3000mcg per day in divided doses but did feel better for the first few days when I took a break but crashed a short while later. I actually took ten days off and had a blood test at day 7 giving >256 active b12 and 666pmol/l

Both up a lot from my initial pre any supplements 153pg serum (note different measurement type) on both tests to complicate things and 67.8pmol active.

This thing is a nightmare

2 1/2 stone off in months. Gp's who think that's a good thing........ off work, struggling with lights, noise and anxiety and today I notice the change in sensation I had in my right thigh on my left.

Where does it all end

1 like

As to switching off - it depends - mechanisms etc not fully understood and likely to be genetic - so also not known how many people would be affected etc.

If you have a functional deficiency then it can actually be treated by increasing the levels of B12 until you reach a tipping point where enough manages to get through to the cell level. I think of it as being like a dam - and if you have enough water built up behind it enough trickles over the top to keep downstream with enough water.

The real problem is starting to supplement when you have an undiagnosed absorption problem - as it makes it very difficult to get a diagnosis - see the pinned posts and this article in particular


Thanks. If it wasn't for these damn burning eyes I wouldn't keep stopping it.

I think they burn when I use the methyl spray (not in my eyes lol).

I've been off yesterday and today and they're still burning but when I took the ten day break I noticed it improved but other things like anxiety and noise/light sensitivity got worse.

Oh the joy

I'm going to try a few more days off if I can tollerate it and then see if the jarrow b12 help.

I did initially try them but felt jittery on them but they were 5000mcg per tablet.

I think I'll order a smaller dose.

My initial plan was to hold off until I get to see the consultant but my symptoms worsened off it so I felt compelled to restart.


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