Active B12 results & pregnancy - Pernicious Anaemi...

Pernicious Anaemia Society

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Active B12 results & pregnancy

Gaia_ profile image

Hi all, I’ve been receiving b12 injections every 8 weeks for the last 6 years and throughout my pregnancy (currently 35wks). I’m under obstetrician care but she’s been very slow to properly speak with me and at 28 wks I finally had a chance to explain that for the few weeks prior to my injections I’ve been feeling unwell and had symptoms I’d normally relate to deficiency and not just normal pregnancy. I shared info from PAS and the British Journal of Midwifery and she agreed to write to my GP to ask to have the frequency of my injections increased through the rest of pregnancy & while breastfeeding. But… first she wanted to speak to the hospital’s haematologist. He’s advised her to do an active b12 test before writing to the GP. This is now booked for when I’m 38wks. I’m not really sure what I should be looking for in the test results when they come? I do have a new GP who seems to be more informed and has moved my next injection forward so I’m ‘dosed up’ before labour so hopeful I stand a chance of being treated symptomatically if I’m demanding enough. Any tips or advice on what the screening might show that I should know about would be gratefully received.

12 Replies

Personally I would refuse the blood test if it were me. The reason being is that B12 blood tests are not relevant and will give false scores once on b12 injections. Id refer your specialists to the guidelines written for them on this! Am sure you are right you need more frequent injections now you are pregnant.....bit of a no brainer really and if your consultant and GP applied a microgram of their brains and thought about it they would realise this! The problem is that most of the medical world have become reliant on trsts and just read what labs say......and rarely d othey actually use analysis. Any excess of B12 you will excrete out. So moving to monthly may well help you a lot assuming you felt well on the two monthly jabs prior to pregnancy.

Gaia_ profile image
Gaia_ in reply to waveylines

Thanks Waveylines, this is the case I’ve been making but it’s frustratingly slow! Fingers crossed I can persuade the new GP if I dont get anywhere with the obstetrician.

The screening will probably show lots of b12 in your blood. A waste of time and money.

The medics shoujd follow guidelines.

That is why they are written!!

B12 was on my daughters routine pregnancy blood tests .

It's a known fact it depletes after child birth and bresdt feeding so your demand won't go down but up.

Vital for breastfeeding the baby gets enough b12 .

Your Gp sounds sensible

Gaia_ profile image
Gaia_ in reply to Nackapan

I agree Nackapan! I’ve shared the relevant info I can so hoping I can provide some push back on the active b12 test they want to run but not entirely sure what to look for 😬

Gambit62 profile image

Pregnancy is a time when it is particularly difficult to interpret any tests of B12 in blood and levels of B12 are usually lower during pregnancy because of the demands of the foetus.I'm not clear either what the haematologist wants to see in the results and I certainly don't understand waiting for the results of a test given that you are experiencing return of symptoms. However, the only person that really knows why the test has been suggested is the haematologist who has suggested it - you could try expressing a bit of curiosity on the grounds that you have heard that the haematology guidelines are not to test once treatment as started and you just wonder what the test might show during pregnancy. Although the guidance refers to testing holo-T during pregnancy where symptoms exist this section relates to patients who don't have a known cobalamin absorption problem.

Gaia_ profile image
Gaia_ in reply to Gambit62

Thanks Gambit62, the obstetrician realises the total b12 test isn’t helpful so the current request is for active b12 test but I’m not clear what I should be looking for with the test results itself - any tips?

Gambit62 profile image
Gambit62Administrator in reply to Gaia_

I don't think you should be looking for anything - it may come back low or it may not - injections muddy the water a lot. Just be prepared to push back if they want to base treatment on it having come back high

waveylines profile image
waveylines in reply to Gaia_

The active b12 test won't be anymore accurate than the usual b12 one, once you are on really don't get what the haemotologist hopes to prove tbh...... Are you able to talk to him/her directly?

Gaia_ profile image
Gaia_ in reply to waveylines

I haven’t tried, I may try and contact the obstetrician again and see if I can. Good idea!


May be something useful on these websites.

PAS (Pernicious Anaemia Society)

Based in Wales, UK.


There is a helpline number that PAS members can ring.

PAS website has some useful leaflets


B12 Deficiency Info website

Unhappy with Treatment (UK info)?

Letters to GPs about B12 deficiency

BSH Cobalamin and Folate Guidelines

Pregnancy is mentioned in above document.

Have you discussed pain relief in labour with health professionals?

The reason I am mentioning it is that gas and air mix contains nitrous oxide.

Nitrous oxide inactivates B12 in the body.

Gaia_ profile image
Gaia_ in reply to Sleepybunny

Thanks Sleepybunny, I am a PAS member so have had a good nose around the site to see what I can find and used some of the resources with the medical professionals I’m in contact with. Will continue to check there so thanks for the reminder.

“No Entonox” has been clearly written on my notes by the consultant and we know to reject it if offered. The baby has also been booked in with neonatal for a screening soon after birth. They’ve generally been very good just a bit slow to get moving and this haematologist advice is irritating!

Sleepybunny profile image
Sleepybunny in reply to Gaia_

"“No Entonox” has been clearly written on my notes by the consultant"

Glad that your consultant is aware of the difficulties.

I checked on the NHS page about pain relief in labour and there is nothing there about potential risks of gas and air for people with B12 deficiency.

Testing B12 during treatment for B12 deficiency is not normally recommended although I guess that might be different during pregnancy.

Links about testing B12 during treatment


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