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Pernicious Anaemia Society
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B12 - concerned

Does anyone here have b12 levels in the 300’s

I have had these levels for years. I’ve had on/off severe brain fog, my tongue swells, some depression. I’ve havnt supplemented aside from a very occasional b12 shot in my doctors office. I had blood work last week and now had an extreme change - my levels came back high over 2000. Just seems very strange. My doctor had the medical assistant call me with the results. I need a doctor who is willing to look into why I’m feeling so lousy and check into b12.

Any suggestions ? ty kindly

16 Replies

300 is well within the normal range.

There are many reasons why levels can zoom up without supplements. You really need to see a doctor about it.


you say you have occasional B12 shots - when was the last one?

a B12 shot puts an enormous amount of B12 into your blood and just after your levels will be well over the measurable range. The levels will then drop - quite fast at first and then much slower. Most of this will be your kidneys removing the excess B12 from your blood.

A B12 shot can kick of a reaction that keeps the B12 in your blood and stops it from passing through to cells where it is needed. If B12 levels are high enough B12 manages to get through but as the levels get lower this stops leaving you deficient at the cell level - this can happen well above the normal range.

You say that your levels have been consistently around 300 - when were these tests done in relation to B12 shots?


The 300 range has never been after the injection. I’ve only had 3-4 injections over prob 10 years. This high reading was last week. I got the injection and then minutes after had the blood drawn. Probably should have been the other way around. Would it have metabolized in my blood that quickly.


yes, it starts to get into your blood very quickly so a serum B12 just after an injection really isn't going to tell you anything beyond the fact that you have had an injection

1 like

Your doctor should know he cant test immediately after an injection. If you cant get his act together you should change doctors.


"A B12 shot can kick of a reaction that keeps the B12 in your blood and stops it from passing through to cells where it is needed. If B12 levels are high enough B12 manages to get through but as the levels get lower this stops leaving you deficient at the cell level - this can happen well above the normal range."

I suspect this may be happening to me. Gambit62, do you have any further information and/or references for this?


please feel free to look at my profile and back through responses -

you could also try researching on functional B12 deficiency -

this is a good resource for research


though I don't know that there is necessarily a lot out there on treating functional B12 deficiency in patients who have problems absorbing B12

It also comes up in relation to conditions that can raise B12 levels - such as liver and kidney problems



Lots of reading to do! Many thanks, Gambit62.


Hi Mguerrero Are you in the U.K?

It is also important that your Folate level is monitored as this is essential to process the B12.

There is a complex interaction between folic acid, vitamin B12 and iron. A deficiency of one may be "masked" by excess of another so the three must always be in balance.

Symptoms of a folate deficiency can include:

symptoms related to anaemia

reduced sense of taste


numbness and tingling in the feet and hands

muscle weakness


Folic acid works closely with vitamin B12 in making red blood cells and helps iron function properly in the body.

I am not a medically trained person but I've had P.A. (a form of B12 deficiency) for more than 45 years.

I wish you well


Hi Mguerreo,

I have recently had the same issue and after a lot of research it appears the uk guidelines for ‘normal range’ (190-750) is grossly out of date. Most other countries use a base line of 500 and if the basic blood reading is below this and you have symptoms of deficiency - particularly neurological symptoms - then you would be treated with B12 injections for life. My reading was 300 so the doc sent me home telling me I was depressed. He couldn’t explain the neurological symptoms and wasn’t interested in trying to find out the cause. I seeked help from a B12 charity (B12d.org) and I now self inject, immediately my symptoms subsided; brain fog, numb hands and feet, pins and needles, tension headaches, poor balance, dizziness, some days my legs were so jelly-like I couldn’t walk etc. All that has gone. I still feel more tired than I should but after having the B12 for a few weeks now I think I may also need to supplement folate as this works hand in hand with B12.

I would recommend you do some research and this will arm you with the info you need to go back to the doctor or the confidence to self inject. There are Nice guidelines and also bcsh guidelines on this which doctors seem to ignore. I have been reading so many stories on here where people are suffering because doctors are ill educated and uninterested in B12 deficiency. The B12d.org website also has a symptom checker and you can request a call back from the doctor (now retired) who set up the charity.

It’s worth remembering that the basic blood test only shows you the amount of B12 in your blood not the ‘active’ b12 I.e what you body can actually use.

Good luck



Forgot to say.. they should never do a reading straight after an injection of b12 this will simply show what has just been absorbed by the blood from the injection! Once people start injections the standard blood test is largely irrelevant and symptoms should be monitored instead...


Hi Mguerreo

There is a b12 'active'test done privately as nhs only does serum b12. Active is more accurate and shows if need further invedtigation for say MMA homocysteine and intrinsic factor. Trying to get a GP in my case to further pursue is near impossible. Yes b12 nhs results are normal. At the end of the day symptoms should trump blood results esp if neuroligical symptoms. My b12 is 393 after taking b12 sublingual for nearly a year so results not really accurate and the result has reduced since august which baffles me despite diet and sublingual supps.


Mine are at 180, but not sure what that means... now have another appointment at end of this month with a nurse to "hopefully " explain it all to me! The last nurse on the phone told me to "Google" it! I'm sure she was very busy but not helpful for me...!


Clematisa1, That is definitely low! Do plenty of research before u go then go armed with that information, it is a lottery with both doctors and nurses as to how helpful they will be with B12 issues, I saw 5 different doctors last year with my symptoms and not a single one knew anything about B12 deficiency or was interested to learn. Be prepared for a battle if u go down the gp or nurse route!


Hope you get this nailed and start feeling better soon; as a side note....at least you know the B12 shot really does get into your bloodstream fast lol


That would most likely be a reading from the B12 shot due to taking blood straight after.

If your levels have been constant at about 300, that is within range and docs would say normal (No Problems) but you can have B12 symptoms at 300.

Also get Folate, Ferritin, and Vit D levels checked. Any 1 of these low could cause you problems (similar symptoms to low B12).

I personally think if the rest are ok you would/could benefit from taking oral B12 supplement to get into the higher range.

Your 2000 reading will drop quite quickly after injection and if you not taking anything will bring it back to your stable 300 range.

You only need a blood test and take it from there.


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