Pernicious Anaemia Society
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B12 weight loss after injections

Hi all I was diagnosed in July 2015 with B12 deficiency (apparently I was just under the 'normal' range but had all the symptoms including exhaustion, pins and needles in hands and feet, memory loss etc) I was originally diagnosed in 2012 whilst pregnant with my third baby as being B12 deficient and was given a loading dose but was told it was just a pregnancy symptom and wouldn't need to be followed up! Anyway fast forward to last year when I started getting the symptoms again I requested the blood test and it can back as being deficient! I was given 4 loading doses (and not the usual 6 as I had them when I was pregnant in 2012 apparently) since then I've been given 3 monthly doses and can safely say it has helped. The pins and needles have disappeared and my tiredness and memory fog isn't as bad. However I've started to notice that I've lost some weight since having the injections - is this normal? I've only lost half a stone and apparently my BMI is still OK as had a new patient health check but I don't think I've done much to contribute towards this weight loss? I was always around 9 1/2 stone and now can't seem to get above 8 stone 13! I have stopped drinking Coke and eating chocolate but only because I wanted to get rid of my bloated belly!! Has anyone else experienced weight loss after having b12 injections?

6 Replies


Have you ever had an IFA test (Intrinsic Factor Antibody) test? this can help to diagnose PA but teh IFA test is not always reliable.

Have you ever had thyroid tests, Coeliac tests and diabetes tests?

I'm too tired to write a long post but these websites might help. I've written other detailed posts recently which may help if you search for them.


01656 769 717


Could It be b12 by sally pacholok and JJ.Stuart

What You Should Know About Pernicious Anaemia and Vitamin B12 Deficiency by Martyn Hooper

Documents /articles

useful summary points

google "BCSH Cobalamin and Folate Guidelines"

Uk document came out in 2014

Were you given the recommended loading doses? Info GPs need is in BNF (British National formulary) Chapter 9 section 1.2 and also in BCSH Cobalamin Guidelines.

See link below for info similar to BNF.

Management section


Hi yes I've been tested for most of the above and was told all were normal apart from my thyroid being slightly under active but apparently it wasn't a concern!!


I haven't lost any weight with B12.

If you have more energy, you are probably more active, which could account for it, but don't discount giving up the cola and chocolate - cola has tons of sugar in it.

I wouldn't think it a concern unless you continue to lose loads of weight without trying, but this is not a medical opinion.

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Hi. I too was diagnosed in July. We had been to Florida in may and once back, we stopped eating big bags of crisps, chocolate and all fizzy drinks. My husband shed over a stone within 6 month but I shifted NOTHING - apart from being very tired, I was devastated. Once I got my loading doses, I only felt slightly better, then I started supplementing with methyl skin patches and I started to lose weight too. It's gradually coming off and so far I've lost 3/4 stone. I read somewhere that b12 can kick start a sluggish metabolism.

Hope you continue to feel well. This is a complicated thing, so keep analysing your symptoms and what can be done to help yourself. ☺


I've been using the b12 spray as well as the injections so not sure if that has made a difference? Well done on the weight loss! I'm definitely feeling more energetic than I was so that may have contributed towards the weight loss. I did also suffer from a stomach bug just before Christmas which took me a while to get over so it's starting to add up a bit!

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No I haven't lost any weight with the B12 injections, but I would be more than happy if I did. I've got underactive thyroid and fibromyalgia too, so any weight loss would be good for me.

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