Thyroid UK
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Free T3 and Free T4 - fasting before testing best?

Hi, going to see GP today to ask for a referral to an endocrinologist - the endocrinologist wants my free T3 and T4 to be tested prior to my seeing them - is that a good sign? What exactly are free T3 and T4? Am I right that it is best to fast prior to any thyroid tests? Can anyone recommend a good thyroid book where I can get sine more in depth information. 

Thanks so much for your help in advance, 


3 Replies

Is the NHS test or private one? 

If need to organise private one see thyroid Uk for more info

NHS rarely does FT3 test - even if requested by GP - which one reason so many here get private tests done 

Blue horizon - thyroid plus ten blood test - easy to do at home - will check all your thyroid levels, including antibodies (which is Hashimotos) plus also checks B12, folate and ferratin - theses are often low if have thyroid issues and need to be at top end of normal range 

Also important to check Vit d levels - see Thyroid UK 

Blood test ideally as early as possible (8am) DON'T take any thyroid medication in 24 hours before hand (take normal dose after blood test) - also no food or drink before test - but can drink water 


Wennieflower, arrange early morning fasting tests (water only) as TSH may be measured in addition to T4 and T3.

TSH is a pituitary hormone which responds to thyroid hormone levels (T4 and T3).  TSH is high when T4 and T3 are low and TSH drops when T4 and T3 are sufficient.


Thank you everyone - they are NHS bloods - having them done at 8.30am (earliest appointment possible). I'll only drink water! Thank you, Wennieflower 


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