Should I fast?

[APAscot]

Am due for tsh, free t3 and free t4 on Wednesday. Should I fast? Asked nurse at last blood test before biopsy and she didn't really know but didn't think so. Think I've read on here that you should fast and have blood taken early morning. Very interesting reading everything on here. People are obviously very knowledgeable/experienced. Thanks for help

[Marz]

healthunlocked.com/search/f...

The above link takes you to almost 4000 other posts about fasting or not - here on this Forum ... There is a - Search Thyroid UK - facility where you type in your desired question. Are you on a phone ? - Click onto MORE above your Post and then click SEARCH on the Drop Down banner - ready to go ....

You have read here correctly - fast and as early as possible. Hope they do FT3 for you - most labs refuse - sadly.

[APAscot in reply to Marz]

Many thanks Marz. Will definitely fast and leave off the carbimazole for 24 hours. Have previously had ft3 tests so obviously lucky in our area.

Thanks to everyone for replying.

[Marz in reply to APAscot]

As you are Hyper and not Hypo of course it is critical they test T3

[bantam12]

I and others dont fast because having done it both ways results show no difference.

[shaws Administrator]

This is a link which which proves that fasting can affect results:

verywell.com/optimum-time-a...

[bantam12 in reply to shaws]

It doesn't actually prove anything, just says "may" affect results, my TSH is 0.03 whether I fast or not.

[jimh111 in reply to shaws]

This link states 'While fasting is not considered necessary when performing a thyroid blood test, studies have shown that early morning fasting translates to higher TSH levels, compared to those taken later in the day with no fasting'. This is where the confusion arises, the higher TSH levels are due to the blood being taken earlier in the day, not due to fasting. This study ijem.in/article.asp?issn=22... shows fasting does not make a difference. It's a bit difficult to understand the text but essentially you need to compare 'delta 1' and 'delta 2'. The eariier studies, including one by this team, made the elementary mistake of comparing TSH before breakfast with TSH after breakfast a few hours later. No need to be hungry.

[shaws Administrator in reply to jimh111]

I thought that was the reason we fasted and had test as early as possible i.e. to keep the TSH higher so that GP wont adjust dose down unnecessarily. You know many doctors, if TSH is lower i.e. test in afternoon may adjust the dose down or we remain undiagnosed if having a p.m. test..

Quote from above "studies have shown that early morning fasting translates to higher TSH levels, "

[jimh111 in reply to shaws]

'compared to those taken later in the day with no fasting.

[shaws Administrator in reply to jimh111]

I will still stick to the regime that has served me well for a few years now.

Especially since my GP told me that T3 converts to T4 so I said, "no doctor" its the other way round.

[jimh111 in reply to shaws]

You should have said 'Oh can I have some L-T3 so that I can convert it to T4'.

[shaws Administrator in reply to jimh111]

Cannot say that as I take T3 only.

He did prescribe but I've been buying my own for quite sometime now otherwise I would have had an instant reduction as I thought I was having a blood test for another reason. I had consulted him for something other than thyroid.

I had a blood test p.m. and I phoned to get the result. He told me to reduce dose as TSH was low. I said 'it will be low as I take T3 only'. He said but the Endocrinologist says - I said I don't care what an endocrinologist says as I had a blood test without being aware it was for my thyroid hormones and the results will be skewed.

I had a blood test 3 or 4 weeks before for my yearly thyroid blood test and they were fine.

Few can trust doctors to know very much at all except TSH and T4.

[silverfox7 in reply to shaws]

I always think as well that some test I have to fast because of glucose so better to fast for all to be more consistent. My surgery happy to do that as well but said to let them know so they can put that on the form as sometimes if something that needs fasting is on the form it saves them ringing up to make sure. That seems iffy anyway as it was was fearing something that needs fasting should the nurse have queried that with me anyway!