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Pernicious Anaemia Society
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Vitamin b12 side effects

Hi I have been taking vitamin b12 supplements 1mg of liquid for a week now however I have been getting really bad pains in muscles and joints my recent blood test came back as 190 and Dr has said that was ok but I was getting really bad fatigue even though I was taking 50mcg of levothyroxine I'm wasent feeling well my T4 was tested and came out at 3.3 although Dr said that was ok so I started supplementing with B12 to see if it was that. Can anyone give me any advice on what to do thanks

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If you are able to absorb b12 from the liquid in sufficient quantities to have an effect it could be that it is actually working.

Lots of people report a worsening of their symptoms in the initial stages of treatment and many stop due to thinking it's not working.

The theory is though that it is in fact working. As stalled processes begin to speed up again and repair begins to take place you can feel more because more sensation gets through.

Likewise as the body begins to process and get rid of things that built up you feel a bit worse.

Those stalled/restarted processes also need more than b12 to work properly so you can actually use up other co factors ie vitamins and minerals.

The key is a very healthy diet as you can't really overdo natural sources from food.

The same applies to sunlight as long as you don't burn so you get a good dose of vitamin D as nature intended.

Many people take a b complex or multi vitamin containing the b's and minerals. Avoid mega doses though as some like b6 can cause problems if taken in excess unlike b12.

Add a banana or two for added potassium but stay clear of potassium supplements except on medical advice.

The admins will offer you more comprehensive advice and if you're not already on the thyroid forum that's the best place for thyroid advice.

At the bottom of the forum page are pinned posts. They give lots of links to great b12 advice and research.


If the muscle pain you mention is muscle cramps, that could be a sign of low potassium. There are a number of foods that contain potassium: draxe.com/top-10-potassium-...


Hi toonarmy. Hello and welcome.

Are you able to give the reference range for your B12 result - it's not easy to interpret properly without those?

It's possible that you could have the symptoms of B12 deficiency, even if your B12 levels are low,or normal in the reference range (not a lot of GP's appear to know that.

Also - did your GP test your folate levels? B12 and folate work together so if your folate is deficent or low, then the body cannot utilise B12 properly.

I see that you have hypothyroidism, which often goes hand in hand with B12 deficiency and it can be quite difficult sorting out which symptoms are due to what as there are a lot of cross-over symptoms between the two....the thyroid forum is the best place to get advice about your thyroid results.

Did your GP do a full blood count (FBC)? If so, it would be useful to see those results (and the reference ranges too) as these can also help to show if there is an iron, B12, or folate deficency.

Did your GP test your for intrinsic factor (IF) - to see if you have pernicious anaemia (PA). This is more likely if you have any autoimmune conditions in your family. PA is an autoimmune condition that causes B12 deficiency.

There are other causes of B12 deficency (medications, surgery, Crohn's disease etc) so it would be useful if you could give a bit more information so that we can offer the right advice.

If you suffer from any kind of absorption problems, then oral B12 supplements may not work for you since your body may not be able to absorb them properly. In addition, the absorption rate from oral supplements is approximately 1%, at best - in the presence of an already low serum B12 (and your levels does sounds low), then the 'at best' small amount that you may (or may not) be absorbing will not be sufficient to bring your B12 levels up very quickly, meaning that you will continue to suffer the symptoms of B12 deficency.

Also - do,you have any neurological symptoms (pins and needles, ringing in the ears, trouble with concentration, bumping into walls or falling in the dark)?

It'll be a bit easier to advise you if you can leave a bit more information for us....and, as I said, any test results if you have them (GP's often say that these are okay when they're not ๐Ÿ˜–).

In the meantime, I'm going to leave you some links with information about PA and/or B12 deficiency which will tell you about diagnosis, treatment protocols, guidelines, and 'myth busting' information that will help you to understand things that your GP may not know about B12 deficiency, so that you are better equipped to ask the right questions and get treatment, if,you need it. In particular, look first at the symptoms list - you. Isn't find that you have symptoms that you didn't know we're symtpoms. Many do ๐Ÿ˜–๐Ÿ˜–.

Please don't be daunted by what looks like a lot of reading. Many of the documents are one page only and very easy to read. There's only one longer one (about nine pages, I think) but it has useful summary sections if you're feeling too ill to read for long sessions. Just read at your own pace - I find it helps to print and read - I often stop seeing when trying to read on a screen.

Anyway, leave more information if you can and ask as many questions as you need to (B12 deficency is complicated and GP's often needs some help to get you well ๐Ÿ˜„).

Doh...and...my links are broken. I'll post this reply and then dodge off to get the links (if I try and leave this reply it will simply disappear). Will,post the links on a fresh reply...๐Ÿ‘

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Hi thanks for the reply, my blood test results are as follows

Serum vitamin B12 is 190 ng/L (150.0-1000.0)

Folate level 8.0 ug/L (2.0-18.0)

Vitamin D 68 nmoi/L (50-75nmoi/L)

I have hypothyroidism from having radiation treatment to my neck when I had hodgkins lymphoma so after a little while my thyroid slowly started going downhill, I'm taking 50mcg of levothyroxine and my th4 is tested at 3.3 which my dream says is ok I have to also take omeprazole (PPI) which can stop levo and vitamins absorbing so I'm really not too well at the min just want to help myself to feel ok thanks for the info much appreciated ๐Ÿ˜Š


Also I have ringing in ears sorry I forgot that one along side my fatigue and aches


Thanks Toonarmy. Your B12 is low enough to give you the symptoms of B12 deficency - some GP's don't know that your result can be in the reference range but that you can still have the symptoms of B12 deficency.

Suggest you read the information In the links I've given you and go back to your doctor and ask for the blood tests I've suggested (in the reply above - in particular FBC and IF). This might help to clarify what's going on.

Also ask for ferritin levels to be tested - this is one marker for iron deficency anaemia, which has symptoms similar to B12 deficency.

Another way to test for B12 deficency (especially if your B12 is within the reference range) is by blood tests called MMA and homocysteine - these will be raised if you have a B12 deficency (homocysteine also raised in cases of folate deficency). Ask your GP to do these (some have never heard of them but he can ring the haematology department of your nearest large hospital to see if they provide the test - then arrange for you to go there to have your bloods taken).

Suggest you persue both the B12 deficency and your thyroid issues - either could be giving the symptoms you have.

Best to Post your thyroid results in the thyroid forum - they're much better at thyroid than we are here so you'll get better advice from them, both about the results and about what treatment should be.

Good luck and post again if you have any more questions (you may well have once you've done some reading). ๐Ÿ‘

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Hi foฤฃgyme, sorry I forgot to put my ferritin levels on

67 UG/L (12.0-250.0)


Hi toonarmy. Ferritin levels not too bad, just perhaps a tadge low. U always feel better when I can get mine up too 90-100 (same reference range) - but others may feel perfectly well with a level of 67.

If your GP does a full blood count (FBC) this will show if you have the small microcytic red blood cells normally associated with iron deficiency anaemia.

Good look with your GP. Let us know how everything goes and put up a new post if you need any further help.


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And here's the links...

b12researchgroup.wordpress.... (Serious Caution Note about the use of Oral and Sublingual B12 Supplements)

evidence.nhs.uk/formulary/b... (BNF B12 Deficiency: Hydroxocobalamin Treatment Regimes)

pernicious-anaemia-society.... (PAS Symptom Checklist)

stichtingb12tekort.nl/weten... (BSH B12 Deficiency / PA Diagnostic Flowchart)

onlinelibrary.wiley.com/doi... (British Society Haematology (BSH) Guidelines: Treatment of B12 Deficiency and Folate Disorders)

onlinelibrary.wiley.com/doi... (UKNEQAS B12 Treatment Alert, Neurological Symptoms and Risk of Subacute Combined Degeneration of the Spinal Cord)

stichtingb12tekort.nl/weten... (Problems with Serum B12 Test)

stichtingb12tekort.nl/weten... (Testing B12 During Treatment)

stichtingb12tekort.nl/weten... (Misconceptions About B12 Deficiency โ€“ Good to Know Before Seeing GP)

stichtingb12tekort.nl/weten... (B12 Treatment Safety / Long Term Treatment for neurological symptoms)

stichtingb12tekort.nl/weten... (B12 Deficiency: Neurological Symptoms Can Present Even When B12 is โ€˜In-Rangeโ€™ and Without Macrocytosis (large red blood cells) or confirmed PA Diagnosis)



I had increased bone pain for a couple weeks at first. Make sure your diet has electrolytes, magnesium and potassium rich foods are important. If you can't get relief your doctor should Check these.

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Thanks ๐Ÿ–’


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