It's true I've just collected(not that I ever doubted advice) print out of results, 1st time I fasted (as ignorant of this b4 joining here) my tsh .07 previous test showed it at .35 range .39/4.20. I almost feel sorry for Dr and HCA at my surgery cause I kept asking about fasting all either said or implied I was stupid and yesterday she said "I've been doing this job for 16 years and I've never heard of that" she hadn't taken my blood but I was tempted to say well how bad is that all those people have suffered and been given false results cause of your ignorance!! I'm certainly gunning for Doc who told me not to believe everything I read!!! He'll be eating his words and I shall make it very clear that his should educate the staff taking blood and other Dr s there few sorry to rant!BUT please just KEEP telling ppl I know it's labourers BUT it is really worth it. Good health and happiness to you all

21 Replies

I'm not sure I understand your tsh was .35 and now it's even lower at .07. Surely that's not good news for you your doctor will now see you as even more below range?

Yes but because I fasted we now have a true picture of my figures before becausr I didn't know you were supposed to fast my results were skewed.

Best wishes

Unless you had done a non fasting test at the same time you can't be sure it made a difference. If fasting does lower TSH then that isn't really the true number as on a daily basis you wouldn't be fasting so result would be higher.

Fasting raises TSH in the blood stream, not lowers it. But TSH is lower later on in the say, which is why, if you are hypo and have a GP who treats on TSH you should have a fasting test as near to 8am a possible. Really, TSH on its own isn't very useful.

Most people don't eat while they are asleep, so it is an accurate record of your TSH first thing in the morning.

But it's not accurate if fasting has raised TSH from where it would normally be after eating breakfast. What is the point of having a TSH of 2.5 at the time of the test when normally day to day it runs at 1 or below, it's a false result, that's my thoughts and I will stick to my method, each to their own 😊

Why - when it varies by around 75% over the course of a day anyway? What you have to remember is that most GPs don't know that TSH varies through the day or after eating, so if you come in with a TSH of 0.7 they are probably going to suggest reducing levo (or certainly wouldn't give you an increase if you need it) whereas if you turned up with 2.1 they might. Fine not to if you self medicate, but worth knowing about if GP insists on dosing by TSH.

Well there was a big difference on fasting and non fasting and the Dr is now more proactive towards me so I consider it a win win situation and will fast next time so recreating the same situation

It's more important that you have your blood drawn first thing in the morning (and fasting if possible) than fasting later in the day. You need to look at the circadian rhythm and thyroid. If you had your last test at, say, 9.30 and having eaten, then this one was at 3pm and fasting, that alone could make a difference. The fasting is less important than the time of day of the test.

As bantam12 points out you don't live your life fasting so now you have a result that your doctor may use to reduce your medication but your tsh is functioning in a body that is not in constant fasting.

I make it a rule to fast before any blood test and to have them as early as possible in the day. I also do not take medication until after the test which is no problem as it is early in the morning

Yes, for several years now everyone has said to have blood drawn prior to eating that day.

Is that no longer the case? If so, how and why?

Thanks, looking forward to hearing about this - it is surely really important :-)

I don't fast before thyroid bloods, I want my results to show my normal daily level, not one that is only accurate for that day when I have a test. This is my personal view and I'm not saying either is right or wrong but why are we bothering with the TSH results anyway if it's meaningless as we are told many times.

It's not 'us' (as in patients who understand our condition) that's bothered with TSH, it's because TSH seems to be the only test that GPs consider and dose by.

Anyone looking for a diagnosis, dose increase or looking to avoid a dose reduction needs TSH to be as high as possible, and it is said that fasting overnight with water only will give a higher TSH. It only really means have your breakfast and a cuppa when you get back from the blood draw.

Surely its not meaningless if your problem starts with your pituatry gland

In which case, TSH won't really change whatever happens to FT4 and FT3, and also won't really be affected by taking meds and fasting. If you have secondary/central hypo, TSH is less than meaningless.

I've never been convinced by the evidence that I've seen for fasting for TFT tests, and whether or not doing so raises or lowers TSH. I'm happy to believe that an effect of fasting/eating on TSH may exist in some way, I'm just not sure what the effect actually is.

However, I do know for certain that there are some tests which should be done fasting e.g. iron testing, fasting glucose testing, cholesterol/lipid testing, and no doubt a few others as well.

If my doctor decides I need some blood testing and arranges for iron testing and TFTs to be done, do I fast (for the iron) or not fast (for the TFT)? I can't do both for the same blood draw, and the doctor is unlikely to allow me to have two lots of blood tests (for cost reasons!) when both can be tested from the same blood draw.

If I don't deliberately fast for TFTs then I can imagine a scenario in which one time I get a blood test I might have a Full English Breakfast beforehand. Another time I might be running late and I just have coffee. The time after that I fancy cereal or porridge. I don't know what effect all these different situations will have on my TFTs. I'm sure it reduces the comparability of results between tests though.

So I side-step the whole question by being as consistent as I can possibly be and by fasting for every single blood test. And for me that means, "Stop eating and drinking after about 10pm the night before (apart from water), until after I have the blood draw".

I have discovered one fly in the ointment though. If the blood test form doesn't specify overnight fasting then some people who take blood interpret this as saying "Thou must not fast!", and they get very twitchy if you have fasted. But if fasting is not required, then I interpret this as saying it doesn't actually matter, and the choice is mine. So I always fast. In my view, it maximises the comparability of my tests.

I must say I've never been asked if I fasted or not for any blood test. I think they just assume I've done what I was told.

I'm fairly new here so any info is good. I have never had any results given or actually asked for any. I had a cyst on my pituatry gland which was only discovered when i lost my periferal vision 10 years ago. This was not my first sympton but it was the one that detected the cause of my underactive thyroid and the reason for my panic attacks and my raging thirst and the need to drink a litre of water every 2 hours and at the same time need the loo all day in and all night. Even once this had been discovered no one gave a diagnosis of why even though booked in for surgery. then a new registrar asked same questions how do feel etc told tired all the time thirsty all time and he said i know what you have diabetes insipedus and prescibed desmopressom a replacement hormone for vasopressin. Previously i had been disgnosed by my gp with a thyroid problem when i had aching feet and was sent for a blood test. I first went to a gp with thirst problems loss of weight very irregular periods when i was 26ish my doc said who wants to bleed every month!! i then became fat.I now take 125 mg of thyroxin 100 mg twice a day desmopressom and 800 of acrete d3 twice a day . Still tired. I had an appointment with endo on monday this week and have been told my AGH is very low and have offered the hotmone which i would have to take via injection every day. Every time i go its someone different asking the same thing. Read my notes!! To have the AGH adult growth hormone i need several tests first i think including insulin stress test. Ive had the nhs adrenal test and that was fine.

Ps i thought pituatry released tft to make thyroid do its job

Tsh damn predictive text

TRH is hypothalamus and TSH is pituitary

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