Thyroid UK
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Low B12, high B9 (Serum Folate)

I got back my results from Blue Horizon and thankfully thyroid function is good, all is in normal range. But surprisingly my B12 is low at 201 and my B9 (Serum Folate) is high at 45.23. The comments with the results say that the B9 can mask low B12.

I have had GP blood tests in the past and have never been diagnosed as B12 deficient. Could this be because of the masking and I therefore could have been deficient for a number of years? I have been vegetarian for 22 years so this is a big possibility. The reason my GP gave me for my whole list of symptoms (fatigue, zero libido etc.) was put down to a D deficiency (tested at 38) which I am currently on supplements for. But in the 6 months I've been on them I have felt no better, so if I'm honest I'm a little relieved that I have another avenue to explore. Does low vit D have any kind of affect on B9 or B12 levels? Why would my B9 levels be so high?

Also I have my next Dr's appointment in a week's time but want to start B12 supplements now to try and feel better. I understand that I should wait until next week but would the supplements raise the B12 level significantly between now and then or does it take a while?

Many thanks


7 Replies


(1) You might actually be hypothyroid despite the normal range results -- what were those thyroid results by the way? If TSH was over 2.0 they weren't normal. Hypothyroidism lowers stomach acid so you don't absorb nutrients as well

(2) Your diet may be low in B12 (likely, as it's mostly found in meat)

(3) You may have pernicious anaemia, an autoimmune disease which presents with B12 deficiency

(4) You may have Coeliac Disease or a another gut problem and your gut absorption is lower because of damage to intestinal villi.

If you're really unlucky, it could be all 4. :)


Sorry, didn't answer your folate question. This wont be the best explanation but my brain's a bit foggy today...

Folate is used up as part of B12 doing it's job - so high folate would suggest that not enough is being used up. That means you may not be utilising B12 very well.


And because you are getting folate from the foods you eat but not getting any B12 - unless you eat eggs? In any case, if you Don't eat meat, you will be absorbing more folate than B12.

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Thanks Jazzw, useful info. Results were:

TSH 2.97

T4 total 107.9

Free T4 16.54

Free T3 5.27


Right, so yes, that TSH is a little high. Possibly because of the low Vit B12 situation (but it's one of those chicken and egg situations). 

I think I'd pursue finding out what's going on with the B12 and folate first. You need proper testing for pernicious anaemia.


It's very unlikely that your doctor knows anything about B12, so if he saw that it was 'in range' - albeit at the bottom - he would have thought it was 'fine', and wouldn't have said anything.

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One vegetarian to another, having recently started taking B12 myself, I would say that you are unlikely to notice much of a difference in a week but, if you are expecting to have blood tests, it might indeed influence results.  If you won't be having tests then go for it :)

Have you noticed any changes in your fatigue since starting on D3?  I tried to supplement because my levels are low but they just put me to sleep!!

Something else I am investigating is selenium, the vegetarian diet can be low in this, particularly as food levels drop.


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