Pernicious Anaemia Society
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How b12 affects the blood results?

Hi everyone,

Could someone help me with a question about b12 injections for my dad.

After finally convincing his GP that he needed injections, and his mother had pernicious anaemia, he will not allow monthly injections, despite the psychiatrist recommending it for 3 months to re-assess his neurological condition after that time.

In the meantime i have sent him Jarrows 5000mg b12 lozenges. This has shown on bloods as having a result of 2000. Today the surgery refused to give him his 3-monthly b12, which was actually 4 months because we have been fighting to get monthly jabs (and obvs failed! ).

My dad has been crying on the phone today, so needing his next jab.

My question is, how relevant are the bloods if you are supplementing, how near are they to giving an idea about the actual levels?

Would it be better to get a private active b12 blood test done?

His homocysteine was borderline and intrinsic factor was high before they agreed to give b12 injections.

The b12 lozenges help him with the anxiety but it is not enough to resolve the deeper neurological issues.

Thanks for any advice


4 Replies

Hi this is what you're looking for

It's actually from the pinned posts. They're right at the foot of the page (on mobile devices anyway).

They're a must read before taking to the forum for technical answers or evidence to present to doctors etc.

It's a great resource.

I read you need months off any supplemental b12 for the serum test to be of use of you're going off the lab ranges. Those ranges are for b12 from food sources in essence.

The b12 numbers can still be of use but just to see if things are rising or falling and how fast. But certainly not to measure effectiveness of any treatment apparently.

Once treatment commences it's all about how the patient feels.

Others on here, especially the admins will be able to offer a more informative reply.

I hope you get things sorted.

It's not nice living with it or watching others go through it.

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Thank you so much, it's been such a battle already and this is just a massive blow to him.

I'm actually off on holiday so trying to send my parents all the information before i leave the UK for a week.

Thank you for that information, I'll email his doctor when i can with the above too.



the IF being high means your father definitely has PA - he should be treated with maintenance shots.

serum B12 results mean nothing once you are on B12 injections unless they come back low - this is reflected in BCSH and NICE guidelines.

Has your father's GP provided an adequate explanation for ignoring the advice given by the psychiatrist? have you written to the practice manager querying this?

Suggest that if you aren't a member of the PAS you formally join


and contact them - will probably advise you to try writing in the first instance but can support further by contacting directly if this doesn't produce the necessary results.

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Thank you so much, i will be contacting his GP when I get back from holiday.

I will follow all your pieces of advice, i thought that was the case.

So grateful for this forum support.

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