Pernicious Anaemia Society
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b12 and nitros oxide

I posted a couple of days ago as although I am bee treated for graves and I am feeling better some of symptoms have. Not improved they are getting worse the doctor has refered me to a neuro she aid what I have is sock and glove neuropathy

And I have no reflex a in my left foot at all

I picked up my blood results today my b12 is now 298

6 months ago it was 338 I have been doing a bit of research online and came across a site that said nitrous oxide used by dentist can cause b12 to stop work it was a bit of a shock because I had dental surgery in November 2012 and my symptons started in jan 2013 and have progressively got worse since then has any one heard of this before ?

Also do b12 results fluctuate so is there any significance

In the fact my b12 has dropped and increase in symptoms

8 Replies

Hi Rush2112,

I asked the same question regarding N/Oxide last year as I had an operation in my foot and afterwards I felt really weak, shaky and out of sorts.

Apparently it doesn't strip the B12 from your blood but does stop it from working some how?

For example if you had a blood test it would show the same amount of B12 as before the N/Oxide, but the B12 would be inoperative!

It took me a while to start feeling better again.

Hope you're better soon :)

1 like

Nitrous oxide is toxic to B12. Also amalgam filling are toxic as the Mercury leaks into the blood and one of the jobs that B12 does is to participate in the removal of toxic metals from the blood. It is consumed in the process. Both of these can be replenished from the liver in normal people but someone with a B12D has great difficulty. An injection of B12 following a visit to the dentist or any surgery is desired, even just to support cell reproduction for the healing process and to fight infection with white blood cells.

Here in the USA some labs add a caveat to b12 test results that 10% of the population exhibits neurological symptoms when results are below 400 pg/ml. You may be in this group. Are you getting regular B12 injections? Do you take supplements?


Hi rush,

I am confused, are you on B12 treatment now? I have read several of your previous posts and in this one your bloods seems to imply B12 def (High RDW, MCHC and Haematocrit) see:

Also having a family history of PA should be kept in mind.

Your symptoms read very much like PA/B12 def, I am surprised that with sock and glove neuropathy you are not being treated, it is a common complication of B12 def. and treatment should be started with obvious neurological signs of a B12 def no matter what serum B12 tests show. The serum B12 test is of little value, it does not show what is actually used in your body, only what is floating round in you blood.

It would be good if you could get the active B12 test done and or MMA, see:

I hope this helps,

Kind regards,



Nitrous Oxide reacts with cobalamin - oxidising the molecule and making it impossible for the body to metabolise and use it. This is well known and a concern in the US where people use nitrous oxide as a recreational high.

Your results and symptoms certainly do imply, as Marre says that you have a B12 deficiency - and it may be that this has been building up for a while but the nitrous oxide made a big difference because it made the B12 that you had inoperative.

Absorption problems can take years or even decades to start manifesting as deficiencies because the body stores B12 in the liver. Also, the absorption problem doesn't mean that there is no absorption going on just that it is impaired so gradually over time your body uses more B12 than it is getting in through your diet.

The serum B12 test is a particularly difficult test to interpret in part because it looks at all forms of 12 in your system - not just the active form that you actually use and metabolise, which could be very low whilst other forms are good leading to relatively high readings but still having a deficiency. Significant numbers of people show strong symptoms even though test come back marked as normal. In Japan they would treat if you had symptoms and results were below 500.

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I did not find out I had A problem with b12 until I was given Entenox and a anaesthetic that contained Entenox, my symptoms that I had been experiencing for some time increased to the point I went to casualty, and eventually saw a Neurologist that tested my b12. The anaesthetists are very well aware of this side effect, though usually assume the effect is minor. I think for people whose body stock of B12 is high, they won't notice a short duration of Entonox. But people who use repeatedly, e.g. recreational use, or drug-seeking patients who call ambulances with pain stories so they get Entonox, are at high risk. Also, if someone is just about marginal, Entonox can tip them into being symptomatic.

Entenox makes the B12 inactive [it oxidises the central cobalt atom] but it still shows up on the B12 test. The B12 blood test works with intrinsic factor, so whatever attaches to IF, whether active or inactive B12, will show up. So you might have al false negative test.

Please do not have any Entenox or a Anaesthetic involving Entenox if you have any symptoms or b12 deficiency!!!


Thank you all for your comments I'm not taking b12 at moment as im waiting to see neuro and don't want to skew results

I think I was just hoping for some reassurance that it could be 12 with these scary symptoms let's hope the neuro is a good one

Jcwg rang true with me asI had being suffering before the dental surgery with a lot of vague symptoms which gp had said was menopause and given me hrt the funny thing is she gave me hrt saying that my bloods did not show I was menopausal but bloods could be wrong funny how they treat that without confirmation but not tsh or b12 with symptoms


I think you are doing the right thing re:"don't want to skew results ", once you have a diagnosis and the treatment does not feel right you can always start tinkering, its taken years to become B12 def, waiting a few months now is not going to make a huge difference, is what I think though. Not every one will agree.

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Thanks marre I totally agree

If you have got a definite diagnoses you have much stronger leg to stand on my doctors wasn't intrested until foot stopped moving even in surgery she looked skeptical untill she did reflex test she put in a postion that I could see. What she was doing and then said oh you really can't move it im sure they think we make things up


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