Fasting blood test

[Ness54]

I asked a question today which has confused me for some time on here, as you insist you fast before a blood test and my gp said you do not have to. I contacted Dr Philip Kelly consultant endocrinologist, Kings Hospital, London. He said for a TSH, T3,T4 blood test you do not need to fast.

[StitchFairy]

I was always told there's no reason to fast. As I never eat breakfast though, my tests are always fasting tests anyway.

[Ness54 in reply to StitchFairy]

I don’t eat breakfast either and I take my meds at night not in the morning, but I do like a coffee in a morning or I can’t function.

[StitchFairy in reply to Ness54]

Oh yes, I do have my 'first of the morning' coffee a while before the test. I don't think that would make any difference at all to thyroid test results. The important thing is not to take any thyroid meds until after the test. Which you don't, so that's ok

[Ness54 in reply to StitchFairy]

Yes I get up a 5 o’clock have my coffee, take my dogs out then go for my test at 8.30-9.00, thanks for your reply feel much more assured that I’m ok doing what I do.

[greygoose in reply to StitchFairy]

The coffee would affect your TSH, yes.

[StitchFairy in reply to greygoose]

By how much? It can't make a significant difference surely?

I thought coffee only affected absorption of medication. If I drink a mug of black coffee (I don't have milk or sugar) every time, then the resuts can be consistent for comparison purposes, and that's perhaps the important issue?

[greygoose in reply to StitchFairy]

Impossible to say by how much. The TSH is totally unpredictable, you never know what it's going to do or by how much.

Coffee does affect absorption of thyroid hormones, yes. But, it also lowers the TSH. And, if you have a doctor that only looks at the TSH, you could find yourself with a reduction in dose when you don't want one. So, no, as far as the doctor is concerned it's not just for comparison purposes. Of cours, if you're self-treating and no doctor ever sees the results, then it doesn't matter two hoots. You'll be looking at the FT3, anyway.

[StitchFairy in reply to greygoose]

Thanks. I'd like to see something that confirms what you say. Do you have a link to a paper perhaps? Always good to have the info to hand in case I need it

[greygoose in reply to StitchFairy]

I don't think I do. I'll have a look.

[SlowDragon Administrator in reply to StitchFairy]

ncbi.nlm.nih.gov/pmc/articl...

With ridiculous current incorrect over emphasis on TSH, anything that keeps TSH as high as possible is necessary

So getting blood tests as early as possible in morning and fasting is recommended as patient to patient tip

[RedApple Administrator in reply to SlowDragon]

Interesting that FT4 levels weren't affected, only TSH. Wish they had included FT3 for a more complete picture.

No mention of coffee in that paper though, which is what the OP is interested in.

[vocalEK in reply to SlowDragon]

Why were the poor people in Group C not receiving any treatment? Group C (overt hypothyroid with low free T4 and high TSH).

[SlowDragon Administrator in reply to vocalEK]

Perhaps that group were based in UK .....LOL

[vocalEK in reply to SlowDragon]

LOL, but very sadly.

[SeasideSusie Remembering]

Ness54

See 9th reply down in this thread, by Diogenes, Dr John Midgely, advisor to ThyroidUK, Scientist, thyroid researcher, many scientific articles about the thyroid and testing published.

healthunlocked.com/thyroidu...

GPs, endocrinologists (who are usually diabetes specialists not thyroid specialists) know very little about the thyroid and how to treat it, they're told it's easy, look at the TSH, ignore symptoms, and a little while pill will make all thyroid patients well.

[Hidden]

Hi Ness. In our region fasting tests for diabetes are recommended. After eating food the blood sugar will peak so having a test after breakfast may still be interpreted as too high or normal. If you have a fasting test for diabetes the results should be under 6 for fasting. If you have a test after a meal, the level should not be higher than 10. Tests for thyroid might alter if you have taken your morning thyroid dose. It may take about four hours for the thyroid hormones to circulate in the body before their effects slow down. Diabetes test are able to test for three months previously. Your endocrinologist has indicated that fasting thyroid tests are not necessary. That is the trouble with being a patient we don't know about testing methods so have to ask the GP if necessary.

[Miffie in reply to Hidden]

Why does your region have fasting blood tests for any diabetic testing? Is it perhaps for diagnosis? At that test a glucose drink is given and retested sometime later. These blood results are instant with any glucose meter

For diabetics, routine testing carried out by diabetic nurse or other for review purposes the test is for Hba1c which shows blood levels over a three month period. This is sent to a lab for testing.

Many diabetics are in serious trouble fasting without making significant changes to medication. For many fasting raises blood glucose levels. Fortunately no fasting rules in my area. I wonder how much this varies across the country and why? x

[Ness54 in reply to Miffie]

It’s for under active thyroid

[Miffie in reply to Ness54]

I read that hawii60 replied to you that fasting blood tests were for a diabetics. That was all I commented on. I never mentioned anything about thyroid testing. I do not understand why you made that comment. Having hypothyroidism and being diabetic I know the differences between the two.

[Ness54 in reply to Miffie]

I asked about fasting for my blood test for underactive thyroid, now people have changed the whole conversation around to fasting for diabetics. So I’m totally confused as to why all of a sudden hawii60 and Miffie are talking about diabetics, when there was no mention by myself about diabetics.

[Miffie in reply to Ness54]

I do apologise Ness54. I just replied to Hawii60 and then to further comment furthef following notification by Hawii60 later without going back to check the full thread. I never intended to break away from your question. Please accept my sincere apologies. There can be no excuse for bad behaviour especially by those like me old enough to know better. x

[Ness54 in reply to Miffie]

Apologies excepted and thank you. 👍🏻

[Hidden in reply to Miffie]

Yes you are right - times have changed. The three month test is the norm now but when I was first diagnosed nineteen years ago, I was allowed to have a glucose meter to test my blood when I need to. They stopped this to the detriment of diabetics who go off the rails, and do not have a testing kit. My testing kit recommended fasting blood levels. I always was told to have a fasting test even now for bloods sent away to lab. I live in Wales, and the diabetic care is pretty good, but it took me a couple of years to find out that though I had cut out sugar, my blood sugar was too high, So when I had multi grain intolerance, I realised that hidden carbs were increasing blood sugar. That tasty sausage roll, a nice savoury treat, was loaded with wheat, high carb, fats, and the sausage meat had little meat in it but had fillers of wheat and fat and glucose. Delicious as these treats were along with low calorie tonic which has sucralose in it which converts to glucose in the liver, a pattern of hidden sugars appeared. When I cut all these foods out, including wheat rye barley, malt, cornflour maize, and sorbitol(corn syrup) my blood sugars miraculously went down. The diabetic nurse was gobsmacked - but still thinks drugs are the answer to type 2 diabetics. I am still overweight and need to lose some weight but have to be careful of metabolism changes. I believe the glucose monitor helped me stay on the straight and narrow. Without it 3 months goes by and no tests in between, make people take drugs thinking they will stabilise their blood sugar. They did not help me at all. You still have to watch your eating carefully even when on drugs, so I thought I would feel better without drugs. It has worked. I walked about two miles round a park today which I would never have been able to do two years ago.

[Miffie in reply to Hidden]

Glad you are much better now than a couple of years back. I think the diabetic care I get is excellent. I have a meter as I take Victoza. I previously had Gliclazide which was always giving me hypos.

Still it is only Hba1c at diabetes reviews here, so no need to fast for bloods. x

[Hidden in reply to Miffie]

Thanks. Glad you are ok with drugs. I had a dreadful gut pain and blood after taking the most prescribed diabetic drug, which was given to me with a generic branding when I already knew it would affect me. I went peculiar after taking too much Gliclazide had the shakes, could not sleep and went hypo. Not too good with some drugs so tend to keep away from them.. I had thyrotoxicosis some time ago and the specialist I saw mentioned that diabetes was often linked to thyroid problems later on in life. He was right! From my reply to Ness see how I must have confused the issue with diabetes. As never was given proper thyroid tests except when hospitalised, the thyroid imbalance was never questioned as tests appeared normal. However I never had the full test to denote antithyroglobulin levels, so my prominent goitre, went unnoticed, and the weight gain was annoying. Since removing intolerances, and eating foods high in iodine, my goitre has shrunk.

As mentioned tests have altered for thyroid tests, and was never aware that fasting tests were ever done. Thanks for helping catch up on information.

[SlowDragon Administrator]

Perhaps he hasn't read this research that clearly says it does make a difference

ncbi.nlm.nih.gov/pmc/articl...

TSH levels showed a statistically significant decline postprandially in comparison to fasting values. This may have clinical implications in the diagnosis and management of hypothyroidism, especially SCH.

As many people wish to take their Levothyroxine (and/or T3 ) immediately after blood test, they need to do so on empty stomach as well

Even NHS guidelines say get tested in morning BEFORE taking Levothyroxine

sps.nhs.uk/wp-content/uploa...

[Ness54 in reply to SlowDragon]

I don’t take levo, I take Armour, but I take my meds in the evening many hours after my last meal, I don’t eat breakfast but as I get up at 5am I do like a coffee and this was what I wanted to know was it ok or do I still have to fast befor my blood test at 8,30-9.00 because I find it a long time to wait before I can have a drink.of coffee, I know I can have water yak.

[RedApple Administrator in reply to Ness54]

I guess it depends on what your doctor is interested in. If he only looks at TSH, and what greygoose says above is correct, you might be best not to have the coffee either. Maybe the length of time between your coffee and the test might make it less of an issue though. If I were you, I'd keep doing what you're doing. Coffee is the most important meal of the day for me

[Jivedancer]

I have never been told to fast for thyroid blood test only cholesterol one I was advised to take my levothyroxine 30 mins before breakfast!

[SilverAvocado]

Overall, if you're happy with your dosage, and you're not at risk of having it altered due to the blood test, you can change the conditions or take it in any way you like.

If you care what the results are, it's best to take it in the most accurate fashion possible.

I would put most doctors into the category of not caring too much if the blood tests are accurate or correctly taken! Although most of the advice patients give is also given by some doctors in some places.

[Angel_of_the_North]

You don't need to, but your results will be different as eating (and drinking tea or coffee) can lower TSH. If doctors looked at thyroid hormones rather than TSH, it wouldn't be an issue, but they don't. Also, many doctors - even endos - don't even know that TSH has a circadian rhythm and varies through the day so that the timing of the test is important - so I really wouldn't value what the doctor says over patient to patient tips

[Quest2019]

I did not Fast. I also have the same Doctor!

[Celestialbeing]

I do not fast (food) for my thyroid BW. I use DTE NatureThroid in a split AM/PM dose. I take the AM dose at 6:30, wait 8 hours to do the BW at 2:30, then take my usual PM dose at 3:30. My levels are consistent and indicative of the proper dose for me.

[Angel_of_the_North in reply to Celestialbeing]

If you feel well, that's fine, but your TSH would show as higher if you were tested in the morning, fasting. As long as your free T3 is in the upper part of its range and you feel well, and your doctor doesn't try to lower your dose because your TSH is low - it's all good.

[Celestialbeing in reply to Angel_of_the_North]

Oh I tried testing that way too. The TSH has always remained .1. I have to keep the TSH suppressed due to losing my thyroid to PT cancer in 2012. Using DTE is best for me b/c when I used synthetic T4 I did not convert synthetic T4 into T3, nor did synthetic T3 work for me. For me, it is best to run the tests at the time I mentioned. I like my FT4 in lower end of range and FT3 in upper end of range. Of course, on DTE, the TSH is usually always < 0.1. As long as I receive the right dose and my thyroid-in-a-bottle levels are good then all is well. Sad that we know more than some of these endos.