Thyroid UK
84,126 members99,104 posts

B12, Folate and Ferritin Advice

Hi all,

I have an under active thyroid and I recently had my B12, Ferritin and Folate tested and was hoping I could get some advice. The results were:

B12 - 308 ng/L (211-911)

Folate - 10.1 ng/ml (5.4 - 24)

Ferritin 163 mg/ml (10-322)

I know my B12 is low but as its in range and the IF antibodies came back normal the doc wont do anything. Does anyone have a recommendation of how much B12 to supplement to improve these levels? I have read sublingual is better and 1000mcg a day?

It would be good to have an opinion on the Ferritin and Folate as I have no idea if these are optimal at all?

I also just has a question about what vitamins and minerals people take daily and on what dose? I have done quite a bit of reading but I am finding all the info quite overwhelming. I currently take D3 1000UI a day as I had my D levels tested a while back and they were low but normal range.

Thanks very much

6 Replies


1.000mcg methylcobalamin should be ample to raise your B12 >500.

Folate and ferritin look good to me.

1 like

Cjtunnicliffe B12 below 500 can cause neurological problems. Recommended is very top of it's range, even 900-1000. With your level of 308 I would buy Solgar sublingual methylcobalamin lozenges 5000mcg to boost it right up. When you've finished that bottle (60 lozenges) buy the 1000mcg strength as a maintenance dose.

When taking B12 we also need a B Complex to balance all the B vits. Thorne Basic B is a good one and contains 400mcg methylfolate which will help raise your folate level.

Ferritin should be half way through it's range so yours is fine. You can maintain your level by eating liver regularly.

What was your Vit D level? 1000iu daily is a maintenance dose for a decent level, if yours is low then you probably need a fair bit more.

General supplements for thyroid and adrenal health, in addition to specific ones for known deficiencies, include

Vit C - 2000mg daily in divided doses, or some people like to take it to bowel tolerance so take more.

Selenium - aids conversion of T4 to T3 and helps reduce antibodies in Hashimoto's. 200mcg is the usual dose of selenium L-selenomethionine.

Personally I also take Krill Oil, Co-enzyme Q10 in Ubiquinol form (that's the converted form) and Probiotics.


Hi both, that's is extremely helpful thanks so much. I am experiencing quite severe B12 deficiency symptoms which is why I asked them to test it in the first place (my sister has pernicious anemia) and I'm really glad I did. The vit D test was a while ago (and I cant find the exact figure on my records) so I'm thinking I will ask them to test it again to double check.

I was taking a b complex tablet before Christmas but I stopped because I stumbled across an article saying that Biotin can falsely elevate your FT4 and T3 and lower TSH. I had some blood test results that indicated that this had happened which is why I stopped taking it (they tried to lower my dose based on these results). Do you know if it is ok to take B complex with biotin but just stop taking it a few days before the blood test, then start again after the blood has been taken?

Thanks again for your help!


have you looked at the information on the PASoc forum - for advice and support in trying to get a diagnosis of a B12 absorption problem? Have you tried writing to your GP to draw their attention to how dangerous using serum B12 as a single marker is?

1 like

Thanks Gambit, this is useful. I didn't know you could even write to your docs. Why is it such a struggle getting the right treatment for thyroid and B12. GPs seem to be so reliant on a narrow set of tests and 'normal' ranges (i.e. TSH only) but don't seem to consider how you're feeling.


generally I think they just aren't aware of the limitations of the tests they are interpreting and have a very poor understanding of stats and how ranges work.

Unfortunately tests also costs money and time ... but really difficult to understand why listening to patient and clinical evaluation is soooo far down the agenda.

1 like

You may also like...