Pernicious Anaemia Society

B12 levels

Hi, Have been directed here as a result of a post on Thyroid UK . I posted the results from a Blue Horizon Thyroid +11 blood test. There was a slight confusion over the B12 level. i.e., 659 pmol/L (range 140 - 725). Their suggestion was that 659 was not optimal, suggesting 900 would be more reasonable, especially for a 69 year old with waxing and waning symptoms including fatigue, weakness, foggy head, some loss of balance, among others. Bear in mind I take multi-vitamins and 250 mpg B12 daily. Any contributions gratefully received!

5 Replies

Do you have a result for Folate - that works with the B12 in the body. The amount of B12 in the Multi-Vit is small but could be enough to skew the B12 result and make things look better than they are.

You could try taking Jarrow Methylcobalamin 5000mcg lozenges under the tongue and see if your symptoms improve - also a GOOD B complex for the Folate.

Gluten can also cause some of your symptoms ( gluten ataxia ) as can low thyroid results.


serum B12 isn't a good guide to what is actually going on with B12 - a very distant proxy measure - though 659 is the level where most people (who haven't supplemented) will be okay ... however that's just statistics. Levels at which people who are being treated for B12 deficiency report feeling okay tend to be much higher on average which is where the 900+ comes from - don't know that there is any hard science on why levels need to be higher after supplementation - but my pet theory is around high levels from supplementation kicking off another auto-immune response that shuts down the transport to cells (functional B12 deficiency) and the answer to that seems to be keeping levels so high that there is enough B12 available to beat the response.

I'd suggest trying for a couple more tests - look at folate - if that is low then symptoms will be very similar to B12 as the two are used together as Marz says. Also look for MMA and homocysteine (both will be elevated if your body doesn't have enough to recycle them into useful building blocks) but the levels can also be elevated by other things - including low folate in the case of homocysteine. There is an active B12 test which looks at amounts of B12 that are bound to transport mechanism and useable at cell level (either called Active B12 or holo-T).

If you are looking for a diagnosis of B12 deficiency then don't supplement until you have had everything tested.


Serum folate, in the same test, was 44.22 (8.83 - 60.8)


so definitely not low. Would suggest trying for MMA and/or homocysteine to see if either of those are high.

Possible that there may be a B12 involvement but because the symptoms overlap with so many other things its difficult to know for sure.

Assuming that your thyroid is under control.


Thanks for the input. I have to say i'm getting really confused. On the B H tests my TSH was 2.16 but the total T4 was 74 ( 64.5 - 142).


You may also like...