Thyroid UK
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Non fasting blood tests due. What if I decide to fast? Would it be to me advantage??

Please see my posting "GP would not refer..." (sorry very lengthy - I was upset!) as I have insisted on further tests as I am supposed to feel normal now - but not.

I have been asked to NOT fast, but what difference will it make if I do, will it help my case or not? Can they tell if I have fasted? :O

She insisted that all my results were normal, and to 'pacify' me agreed to VitD, Cacium, B12 (I think) Ferrous and a couple of other tests. She was vague.

Thank you,


8 Replies

I really do not have any idea. The only time I am asked to do a fast before a blood test is if they are going to check my cholesterol, so all my other tests have been done without fasting.

I am sorry you were upset and hope you settle down a little over the weekend.



Which bloods are you having done?


Just added to question above. Thanks.


I fasted, not intentionally of course, I dnt eat breakfast, I do feel it will make a difference to your results, my came back out of sinc. Dont think they can tell, after all I presume its the TSH test you are having done?



Hi,no the labs won't test TSH again because I'm 'normal' at 3.7. Also see my response to all below ... somewhere. ? )


x x


Hi Fasting used to be for cholesterol and diabetess tests. Now, the new rules are that fasting is not needed. I used to fast before my diabetes so severe, now told I must not, there is no difference in my results. However I know not to take any thyroid meds or Beta blockers on the morning of the test until afterwards. I have so many blood tests ,the results are blatant.I also have a lot of other weekly tests and the other meds I have ( a great many ) do not effect those tests.



In my experience a fasting blood test measures you fat and sugar levels in your blood, it is for your cholesterol levels, I don't think, as you are measuring your thyroxin levels it will make any difference to your blood results for this test but not eating sensibly WILL make a difference to your well being. 'They' will only know if you tell them and why would you want to fast anyway? Thyroid problems already play havoc with your metabolism.


Thank you every one for the responses, and explaining to me before the tests.

Because of waves of nausea (??) since developing HypoT. I have only a drink in the morning until my body wakes up. Usually about break time - 10 ish. Otherwise I have a healthy appetite! Some blips have been pointed out by other good people on this site and I have made a note - but I just wondered if it would make a difference.

Only if fasting showed clearly hidden blips in previous thyroid tests would I have fasted.

The tests are not for Cholesterol or Diabetes, I know they are OK. So that's prob. why I have been told not to bother with fasting; as it's not necessary.

That's absolutely fine.

Thank you all.



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