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Thyroid UK
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Complete Blood Test with Ferritin on NHS

Hi All,

So my NHS GP has agreed to do a full blood test with ferritin for me, is there anything else specific I should ask to be done, does the NHS do b12 blood tests?

Also, should i stop supplementing in advance of the tests and if so how long? I am assuming since they wont be checking my T3 I can continue NDT therapy?

Thank you in advance everyone! xx

4 Replies


Ask your GP to check ferritin, vitamin D, B12 and folate.

If you are supplementing iron stop taking it 7-10 days before testing. If you want a baseline B12 result you need to stop supplementing 4 months prior to testing. If you just want to see that you are supplementing an adequate amount skip taking vitD, B12 and folic acid on the morning of your test.

If you are having TSH and FT4 tested leave 24 hours between last dose and blood draw which should be early in the morning fast (water only) as TSH drops after eating and drinking.


I am not a medical professional and this information is not intended to be a substitute for medical guidance from your own doctor. Please check with your personal physician before applying any of these suggestions.


What do you mean by "full blood test"? Do you mean full blood count?

Make sure you know exactly what the GP has agreed to do. A full blood count just gives measurements for red cells, white cells and platelets.

If you have symptoms of fatigue/tiredness and pain ask for ferritin, vitamin D, folate and B12. In addition request to have calcium and phosphate (alkaline phosphatase) measured for your "bone health", and iron panel tests.

It goes without saying you want your thyroid hormones all checked.

Be aware that the lab can refuse to do any of the tests the GP has requested.


Thank you Clutter and bluebug, I don't understand why it is so difficult to get the actual blood tests you need through the NHS?!! I constantly feel like I am being palmed off, why go through the process of taking blood and doing completely useless tests/diagnostics and not do the ones that matter?!! xx


ferritin, vitamin D, B12 and folate.

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