Normal-high b12 serum, vegetarian, needing to self inject repeatedly - can functional deficiency cause a high serum level?

Hi all, I wondered if you guys can shed any light on my B12 mystery and blood test results when my serum level is the high side of normal? I don't get how this is possible as I've been vegetarian (I eat eggs and dairy) for 22 years but I'm wondering if my deficiency is functional, and if that can cause a high reading.

My GP refused to treat my B12 so I have trialled self injections. I was thinking it was dietary and I would be spreading out the injections by now but after ten loading doses I still crash badly after 2-3 days!! As I I have read you can't overdose, I have succumbed each time and just injected again as they are making a huge difference, I have my mental focus back and my energy is slowly returning. Sadly I never checked homocysteine or MMA beforehand.

I've just ordered an MMA urine test now which I've read could still potentially show as elevated if I have a functional deficiencyand am thinking of asking my GP for the IF antibody test. I'm also awaiting genetic results to check into the MTHFR gene from 23andme. What I don't get is how my B12 levels have actually increased over the last year before I started the injections or any serious supplements (I may have had the odd berocca but nothing more than that). I thought both results were on a par until I realised they were measured in different units and the most recent reading is really high when converted to pg/ml if I've done it right (I used an online calculator).

The only big change is that I managed to get my ferritin up from 8 at that time to over 100. Could that affect the result? Or can you somehow get a false high b12 reading from having absorption issues? I've just read a (albeit very old!) paper from 1967 (https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0029665167000412) stating that the average vegetarian has a B12 reading of 250 pg/ml so how on earth could my reading be 756?! The jabs are clearly making a difference, I have my mental focus back, and supplementing in between doesn't enable me to go any longer between jabs hence the suspicion of a functional deficiency. Am I going mad to even worry about all this?!

June 2016

Serum B12 511 ng/L (or pg/ml) (211-900) (I did an online converter which said it's 377 pmol/l)

Serum folate 7.5 ug/L (4-20)

Feb 2017

B12 558.2 pmol/L (140-724) (756 pg/ml)

Folate (serum) 11.04 ug/L (3.89-26.8)

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  • functional B12 deficiency is a B12 deficiency at the cell level when levels of B12 in serum are high. The most probable cause is an auto-immune reaction to the high levels in serum that occurs in some people and prevents the B12 passing through to cells (bound to a protein to prevent this). Keeping levels in serum very high is one way of dealing with this - I think of it as the auto-immune response being like a dam and keeping the levels really high means enough is able to trickle over the barrier and get through to your cells.

    There is B12 in eggs and dairy so if you are just going on levels of B12 to say that you had a B12 deficiency before you started then its quite possible that you didn't have a B12 deficiency. Did you have symptoms before

    The levels you quote above are all in the normal range. There is quite a lot of B12 in berocca so if you didn't have an absorption problem then it could well have resulted in enough B12 being stored in your liver and then released from your liver to raise your B12 serum levels.

    People vary a lot in how much B12 they need in serum under normal circumstances for B12 to be getting through to their cells and most will be perfectly okay at levels of 250pg/mol.

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