Thyroid UK
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Can i ask my doctor for a blood test to test for vitamin deficiencies?

I was on 125mg of levo and recently had a blood test just for T4. The doctor gave me a phone blood test result that said i needed to reduce the levo by 25mg. He said to have a re-test in two months time. I have since asked for vitamin D & B and cortisol to be tested and for a copy of my blood test result as I have no idea of my levels. I also asked the doctor why he doesn't test me for T3 - he said they don't do this now. The doctor wants to see me to "discuss" the additional tests for vitamins and cortisol. Can anyone give me some tips on what i should be asking for/saying?

Many thanks

4 Replies


Do you mean your GP reduced Levothyroxine dose because the TSH result was low? Phone the surgery and ask the receptionist to read you your thyroid results and ranges (figures in brackets after results). FT3 seems to be rarely tested in primary care these days. If you want FT3 tested you can order private tests from Blue Horizon and Genova via

You can ask for vitamin and mineral testing but your GP will only agree if s/he thinks they are clinically necessary. Hypothyroid patients often have low vitamin and mineral levels so we usually advise members to ask for ferritin, vitamin D, B12 and folate to be checked. A serum cortisol test will rule out abnormally low or high cortisol. Many members prefer a private saliva cortisol test which indicates cortisol levels throughout the day. Your GP is unlikely to accept the results of a saliva cortisol test.


Thank you for this. If I have my own T3 test how will I be able to interpret the results and will my GP want to do anything about it? Also is there a recommended website to get my cortisol level checked? If my GP does not accept the saliva cortisol test then is there any point in having it done? Will the doctor test for a serum cortisol it again do I have to source that myself? I think the TSH level was low hence the reduction in Levo but I have asked for a copy of the tests to compare to previous tests


To argue for clinical necessity for vitamin B12, folate, vitamin D and ferritin tests you need to have signs and symptoms that cannot be attributed to lthe change in your levo doses alone. As he has asked you to reduce your dose he will most likely refuse to do them this time.

In addition to this lots of doctors still don't understand the significance of ferritin levels so will not test for it. Instead they will just test your haemoglobin level. Ideally they should actually be testing both if you are pre-menopause regardless of when they last tested you, or if you are post menopause and haven't done a full blood count in the last 12-18 months.

If he refuses you are best getting your own tests. If the results are then out of range as you have asked for them - and make sure you ask for them again and it is recorded on your notes you have asked even if he refuses - then he will have to treat you and this will save you money on retesting.

Please note "out of range" is not the same as "not optimal".


Thank you - what is the difference between haemoglibin and ferritin? I think I am probably pre menopausal. Where do I get my own tests done and will they reliable? Is there any particular test that you think is important to have?


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