Thyroid UK

Active Vitamin B12

My next dim question ( sorry), but you guys have been so much help, unlike my GP until I went armed with info from here! Question about B12 I had it tested and the level was 58.9 ( 25.10-165.00). I know it is “normal” but is it enough. As you know I am taking Vit D, 150mcg levo, have a ferritin of 29 (10-300) and am considering going gluten free. Thanks as always

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I meant Active Vitamin B12


Look for the St. Thomas' Hospital ranges. They have a 'grey area' range which your score may fall into.

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St Thomas link says any Active B12 between 25-70 should be referred for further testing with MMA test

You could get homocysteine and MMA tested via Medichecks or Blue Horizon

But on Levothyroxine many of us just find we need B12 high and supplement regardless

Using test of Homocysteine levels to check for low b12

Good explanation on homocysteine

Oral as good as injections

B12 generally

Methylmalonic acid and B12

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Thanks as always Slow Dragon. I’m getting frustrated with the GP, I realise it is “guidelines”, but I wish they could be more supportive with advice regarding levels and supplements. I’m happy to buy them myself but would like it recognised .

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It would be unusual for your GP to test for “active” B12. They usually just test a serum B12 level that measures both the active (available for use) and inactive (unavailable for use) B12 in circulation.

To get a better idea of useable B12 at a cellular level, the active (holotranscobalamin) B12 test (HoloTC) measures only the active and is available on the national health at St Thomas’ Hospital with a referral from your GP. If this is found to be low then Intrinsic Factor and Parietal Cell Antibodies, MMA and Homocysteine can all be tested on the National Health and will highlight an inability to absorb B12 via the gut and also give Folate status.

Folate and B12 are both involved in the conversion of homocysteine to methionine and a deficiency of either can lead to elevated levels of homocysteine. Also, both can lead to the development of anemia.

If there is an issue it is important to determine whether it is the result of folate or B12 deficiency but both your serum levels of B12 & folate are too low anyway and the easiest supplement form of B-12 & folate to aid absorption is methylcobalamin & methylfolate.

Your FT3 & FT4 are too low so you are undermedicated. Your ferratin is also too low and very important in conversion of T4-T3. Members find supplementing Ferrous Fumarate taken with 500mg-1,000mg vitamin C will aid absorption and minimise constipation. Take iron tabs four hours away from Levo.



Thanks radd. I had my active B12 tested privately and various other things. My GP retested the VitD and FBC, LFTs, T3, TSH and FT4, ferritin and folate . I have just ordered an iron stauts check from Medichecks ( transferrin, total iron binding capacity ) to get further information.

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