Thyroid UK
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Help with supplements please

I am scared I will overdose on B12 and vitamin D this won't happen will it? I really think I should take some. Thankyou

Serum vitamin B12 207 (190 - 900)

Serum ferritin 25 (30 - 400)

Serum folate 2.3 (2.5 - 19.5)

Total 25 OH vitamin D 40.3 (25 - 50 deficient)

Taking 800iu vitamin D3, 1000mg B12, 5mg folic acid and 210mg ferrous fumarate

4 Replies

Vitamin B12 is water soluble so your body excretes the excess that it cannot store.

Vitamin D is not water soluble and is stored in your body so you should check your levels every 6 months if supplementing and adjust the dose accordingly.


Karla1990 No, you wont overdose, in fact you're not taking enough.

Serum vitamin B12 207 (190 - 900) - 1000mg B12

Serum folate 2.3 (2.5 - 19.5) - 5mg folic acid

Well, the folic acid I assume is prescribed but the B12 wont be.

Do you have any signs of B12 deficiency Bear in mind that taking folic acid can mask signs of deficiency so you will have to think back to before you were taking it.

If you have signs of deficiency then please post on the Pernicious Anaemia Society forum for further advice, quoting these results, your ferritin and any iron results, and any signs of deficiency

You may need testing for pernicious anaemia and you may need B12 injections.

I have read (but not researched so don't have links) that BCSH, UKNEQAS and NICE guidelines recommend:

"In the presence of discordance between test results and strong clinical features of deficiency, treatment should not be delayed to avoid neurological impairment."

And an extract from the book, "Could it be B12?" by Sally M. Pacholok:

"We believe that the 'normal' serum B12 threshold needs to be raised from 200 pg/ml to at least 450 pg/ml because deficiencies begin to appear in the cerebrospinal fluid below 550".

"For brain and nervous system health and prevention of disease in older adults, serum B12 levels should be maintained near or above 1000 pg/ml."

If you have no signs of deficiency and the PA forum suggest no need for further testing, then your B12 is seriously deficient and desperately needs increasing. You would need to start with 5000mcg methylcobalamin sublingual lozenges then when the bottle is finished change to 1000mcg as a maintenance dose. But do not continue self supplementing until you have had advice from the PA forum.

Folate should be at least half way through it's range.

You can't overdose on B12 as any excess is excreted.


Serum ferritin 25 (30 - 400) - 210mg ferrous fumarate

Have you had an iron panel, full blood count and haemoglobin test carried out? You should with this ferritin level so ask your GP if he hasn't already done it. You need to know if you have iron deficiency anaemia. If you have then you will need 2 or 3 ferrous fumarate daily, and with that under range ferritin you will probably need the maximum amount.

Also, it will help if you start eating liver regularly, maximum 200g per week due to it's high Vit A content, and eat lots of iron rich foods

Take each iron tablet with 1000mg Vitamin C to aid absorption and help prevent constipaton. Always take iron 4 hours away from thyroid meds and two hours away from other medication and supplements as it will affect absorption.

Ferritin should be half way through it's range with an absolute minimum of 70 for thyroid hormone to work.


Total 25 OH vitamin D 40.3 (25 - 50 deficient) - 800iu vitamin D3

The recommended level is 100-150nmol/L.

Well, 800iu D3 isn't going to raise your level. It is hardly a maintenance dose for someone with a reasonable level. You need serious supplementation and my suggestion is D3 softgels like these and take 5000iu daily for 3 months then retest.

Once you've reached the recommended level you then you'll need a sensible maintenance dose which may be 2000iu daily, it's trial and error so it's recommended to retest once or twice a year to keep within the recommended range. You can do this with a private fingerprick blood spot test with City Assays

There are important cofactors needed when taking D3

D3 aids absorption of calcium from food and K2-MK7 directs the calcium to bones and teeth where it is needed and away from arteries and soft tissues where it can be deposited and cause problems.

D3 and K2 are fat soluble so should be taken with the fattiest meal of the day, D3 four hours away from thyroid meds.

Magnesium comes in different forms, check to see which would suit you best and as it's calming it's best taken in the evening, four hours away from thyroid meds

Check out the other cofactors too.


Thankyou the only things that came back out of range for complete blood count was MCV 78.1 (80 - 100) and MCHC 376 (310 - 350)

Iron panel was in range 6.2 (6 - 26)

Transferrin saturation 16 (10 - 30)


That suggests iron deficiency anaemia. If you are only prescribed 1 x ferrous fumarate then your GP hasn't given you enough.

NICE Clinical Knowledge Summary for iron deficiency anaemia treatment (which will be very similar to your local area guidelines):

Have a read through but this is the treatment:

How should I treat iron deficiency anaemia?

•Address underlying causes as necessary (for example treat menorrhagia or stop nonsteroidal anti-inflammatory drugs, if possible).

•Treat with oral ferrous sulphate 200 mg tablets two or three times a day. ◦If ferrous sulphate is not tolerated, consider oral ferrous fumarate tablets or ferrous gluconate tablets.

◦Do not wait for investigations to be carried out before prescribing iron supplements.

•If dietary deficiency of iron is thought to be a contributory cause of iron deficiency anaemia, advise the person to maintain an adequate balanced intake of iron-rich foods (for example dark green vegetables, iron-fortified bread, meat, apricots, prunes, and raisins) and consider referral to a dietitian.

• Monitor the person to ensure that there is an adequate response to iron treatment.

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