Thyroid UK
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Vitamin B12

Hi all

I had a telephone appointment with my dr because i have been extremely tired again with sleeping during the day and very very bad brain fog ,i have also been experiencing diabetes symptoms ,i was hoping for my vitamin B12 to be checked I've been told they just don't check vit D


I was diagnosed under active thyroid 12 months ago currently taking 75mg levo ,folic acid ,iron tablets ,Omeprazole all prescribed by the dr. I take levo 6.00am and breakfast at least an hour later if not more iron tablet at lunch and folic acid and another iron tablet at 10.00pm with omeprazole which I've been prescribed for a hiatus hernia.

will vit b12 be included in the FBC ?


11 Replies

No B12 is not included.  If you are taking a PPI it will deplete your B12 - as it blocks the acid that is needed in the stomach for good digestion and the metabolism of B12 ....


Thank you for replying :)



B12 is a separate test and is not included in the FBC.

Arrange an early morning and fasting (water only) test as TSH is highest early and drops after eating and drinking.  Take Levothyroxine after the blood draw.

You can order vitD from City Assays and B12 is included in Blue Horizon Thyroid Profile Plus 10 via

1 like

Just as i feared thank you for replying quite sure lack of vit b12 is whats causing the brain fog sure its not my thyroid as I've cut out sugar , dairy, and went gluten free over 2 weeks ago and lost 9lb in total so far but i have a puffed up face again today, i just don't understand why the drs don't know this stuff sure they've got me down as a hypercondriac 


Have you been taking Omeprazole for long?  It's only intended for short term use.

I've got a hiatus hernia - the consultant suggested Omeprazole but I looked it up and decided not to take it.  It reduces stomach acid, but many of us have low stomach acid, not high, so it's the wrong treatment.  It certainly was for me.

Here are 2 links to previous discussions on this forum about low stomach acid, Omeprazole etc which you may find helpful.

And this is a page about low stomach acid from Dr Myhill's site

It seems that most medics haven't heard of low stomach acid.  I'm getting mine tested so I've got evidence if I need it.


I have been taking it for nearly 3 years ,after a course of iron tablets give it 4 weeks and I'm anemic again I keep saying it's the omeprazole and the dr disagrees with me not that they want to find out if there is another reason so I just put in for a repeat prescription now without a break these dr's don't like to think we actually have a clue how our own bodies work 


3 years is far too long.

Quotes from the Patient information Leaflet (online)

'Omeprazole may reduce the absorption of vitamin B12 (cobalamin), '

'If you are on Omeprazole for more than three months it is possible that the levels of magnesium in your blood may fall. Low levels of magnesium can be seen as fatigue, involuntary muscle contractions, disorientation, convulsions, dizziness, increased heart rate. If you get any of these symptoms, please tell your doctor promptly. Low levels of magnesium can also lead to a reduction in potassium or calcium levels in the blood. Your doctor may decide to perform regular blood tests to monitor your levels of magnesium.'

Don't throw away the leaflet which comes with your medicine - show it to your doctor.  You want to get well.  If your doctor won't listen, try another doctor at your practice.  You need tests for B12 and magnesium at the very least.

1 like

I will have a look, i have always put my faith in them and thought they would know this sort of thing surely they can see i put in a repeat prescription regularly on the computer when i go .

I have been diagnosed with chronic fatigue syndrome but do doubt that i have it and the fatigue is being caused by something else thank you for your help i will defiantly follow this up with them as i feel like death all the time i get so tired i just want to cry 


I think that GPs have so little time for each patient that they can't always notice things like that.  It helps if we can do our own homework and point them in the right direction. 

1 like

Why not just try taking some B12 anyway and see if it helps?  You would have to have a ridiculously low level for your GP to treat you for it anyway. It isn't possible to take too much B12, so you won't do yourself any harm. I recommend the Jarrow brand sublingual B12, which you pop under your tongue and let them dissolve there. This  bypasses the stomach, so acid problems won't effect how much you absorb. I noticed a difference within a few weeks of taking them. 

1 like

Thank you will I be able to purchase this from any health food shop ? 


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