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Thyroid UK
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Blood tests!

Hi, I'm new on here :-),I had the radioactive drink about 10 years ago, I'm starting to feel unwell-poss under active, I remember my doctor said that there are two types of blood tests 1-only show if there is a 10% change in levels, where as the other is more detailed, before I had the drink my level was about 9% difference, so only the more in depth test showed up, how ever my new doctor hasn't heard of this before (I think it's more expensive for them to do), if someone could confirm this for me and name what test I should ask for I would really appreciate it. TIA

4 Replies

Have you not been having yearly blood tests since then? I'm not sure I understand what tests you mean.

For general thyroid function, most GPs will test TSH and T4 levels. It is also advisable to get T3 levels checked but many GPs wont or are not able to do this. Endos can or you can get them done yourself.


Welcome to our forum, and am sorry you aren't feeling so good at present.

I always think if someone has had their thyroid gland knocked out or removed it can be a bit more problematic.

I am not too sure what your first doctor said about the two types of blood tests but it was probably only the TSH and T4.

As you have been on levothyroxine for about ten years now (I assume) and you are having clinical symptoms you need a Full Thyroid Function Test (GP may not do all of them but you can get those he doesn;t do privately and we have recommended labs).

You can tell GP you've taken advice from the NHS Choices Thyroiduk.org.uk for info on dysfunctions of the thyroid gland and because you are having clinical symptoms you would like to have:-

TSH, T4, T3, Free T4, Free T3, Thyroid Antibodies, B12, Vit D, iron, ferritin and folate.


Tick off the symptoms you have.

The blood test should be at the earliest possible, fasting (you can drink water) and allow a gap of 24 hours approx between last dose and test and take afterwards. This may prevent doctor adjusting dose unnecessarily.

Always get a print-out with the ranges and you can post for responses from members.


makes no sense to us whatever

we need the actual blood test results you have and to which you are legally entitled

if its taken 10yrs for you to become underactive you are very lucky

many people after RAI become underactive very rapidly

the tests that should be done are








as all are inter related and levels must be correct


Thank you, I have been tested every year or so but the test come back normal, as they did before until I had the other test which showed the change/difference!,I will ask for the actual numbers of the results, seeing the doctor on Wednesday .Thanks.


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