Is an early morning blood test on an empty stomach just for a higher TSH?

[Pinkpetite]

Hello, can I just ask is it just B vitamins you don't take a week before your blood test? I've stopped vit D, zinc and magnesium too just in case. Also is the advice 'empty stomach early in the morning for the blood test' just to get a higher TSH? If so, and as my TSH is always less than 0.01, is it alright to have a tea or coffee beforehand? Or will the coffee affect the result?

I have to go to a hospital that is further away than usual so if possible would need at least a cup of tea, would that be better than coffee?

[jimh111]

An early morning blood test will give a higher TSH (if that is desirable). I've seen no evidence that short term (< 1 day) fasting affects TSH. There was one badly designed study which appeared to show TSH was affected by food. This was corrected by the same team who did a follow up study a few years later showing food had no effect.

Coffee affects absorption of levothyroxine but I have not seen any studies that suggest it would affect TSH.

If your TSH is always below the limit of detection I can't see any benefit in losing sleep and going without food in an attempt to change something that can't be measured!

[Pinkpetite in reply to jimh111]

Yes. The consultant is not concerned about my TSH. Only my T3 and T4.

[SeasideSusie Remembering]

Pinkpetite

can I just ask is it just B vitamins you don't take a week before your blood test?

It's actually biotin that affects blood test results and B Complex contains biotin. So any supplement containing biotin should be left off for 3-7 days before any blood test.

I've stopped vit D, zinc and magnesium too just in case

No need. Just take them after the test on the day. The reason biotin affects results is because most labs use biotin in the testing procedure and this is what causes the problem.

Also is the advice 'empty stomach early in the morning for the blood test' just to get a higher TSH? If so, and as my TSH is always less than 0.01, is it alright to have a tea or coffee beforehand? Or will the coffee affect the result?

Certain foods affect TSH and coffee or other caffeine containing drinks affect TSH. Tea contains caffeine as does Cola drinks and some energy drinks, etc. Best to have water only before the test. However, if your TSH is always suppressed and nothing makes it move then you may not want to bother. My TSH is always suppressed but personally I follow the advice always given here.

[jimh111 in reply to SeasideSusie]

We've debated the absence of evidence that food affects TSH for a long time. What concerns me now is that this is based on 'Chinese wispers' and is now spreading to assertions that caffeine affects TSH.

There have been silly studies in rats showing various effects. e.g. pubmed.ncbi.nlm.nih.gov/641... showed that injecting the equivalent of 20 cups of coffee into newborn rats increased TSH. A similar study pubmed.ncbi.nlm.nih.gov/610... found it lowered TSH. Unnecessary cruelty is my view.

A review pubmed.ncbi.nlm.nih.gov/610... states "In man, typically consumed oral doses of caffeine have little or no endocrine effects. A person must consume 500 mg caffeine (equivalent to 5 cups of coffee) in one sitting for there to be any possible endocrine effects."

I usually study a paper before citing it but it seems a pointless waste of time in this case. Is there ANY evidence that coffee lowers TSH in the short term? Is this not just a case of one internet doctor referencing another who has skimmed a vague reference they have seen in another online profit site? Is their any study that demonstrates that normal coffee drinking affects TSH?

A desire to be cautious and helpful is in danger of promoting hysteria and consequent dismissal of valid concerns. We need to follow the evidence.

[SeasideSusie Remembering in reply to jimh111]

We've debated a couple of things before and we're never going to agree. Others say the same thing yet you always pick up my posts, never anyone else's. I remember asking you before not to respond to any of my posts and you don't seem to be able to respect that. If you want to make your point, don't do it where it says "Reply to SeasideSusie". Please respect my wishes this time.

[jimh111 in reply to SeasideSusie]

Sorry, I'd forgotten all about that. The coffee thing is new, over the last year or so and there's a danger that it becomes accepted albeit false. I'll make a mental note to not reply but it would help if you could cite orginal research if you introduce new concepts.

[Pinkpetite in reply to jimh111]

I would only have one coffee beforehand anyway. Thanks.

[Pinkpetite in reply to SeasideSusie]

OK thanks.

[CL3V3R-G1RL]

You know I've always thought about that. I'm from the United States and everybody here has told me to get blood work done in the morning. But I'm getting mine done in the afternoon. Cuz that's the only time they had open. So my appointment is on Monday at 1:30 in the afternoon. I can fast that long cuz I've trained myself to do that. But I wonder how much of a difference it makes in the TSH levels.

[SeasideSusie Remembering in reply to CL3V3R-G1RL]

CL3VER-G1RL

But I wonder how much of a difference it makes in the TSH levels.

Go to this website and scroll down to the first graph showing daily rhythm of TSH levels:

thyroidpatients.ca/2020/07/...

You will see that TSH is highest around midnight-3am then lowers, with a slight rise about 9am, then lowers throughout the day and starts to rise again about 8pm.

So you can see that if you can get an appointment at 9am you will have a higher TSH than one at 1.30pm which is just about the lowest level of the day.

If your doctor adjusts dose by TSH then the afternoon blood draw will do you no favours. You need the highest possible TSH if you're looking for an increase in dose or to avoid a reduction in dose.

[Pinkpetite in reply to SeasideSusie]

My Dr is focusing on the T3 and T4 as my TSH has been 0.01 for over 20yrs!

[SeasideSusie Remembering in reply to Pinkpetite]

In that case you don't have to worry about anything affecting your TSH.

My TSH has been suppressed for at least 20 years, I wish my GP would focus on FT4 and FT3 instead of TSH, all I get is "your overmedicated, your TSH is suppressed" and my request for her to look at the FT4 and FT3, which are always well within range, are completely ignored in favour of the TSH.

[Pinkpetite in reply to SeasideSusie]

Yes, it's like this at my Gp's.

[Black_puma in reply to Pinkpetite]

Same for me too, it's beyond ridiculous now

[jimh111 in reply to CL3V3R-G1RL]

Menstrual cycle has far more effect on TSH, see the bottom two graphs frontiersin.org/files/Artic... .

A further consideration is that these studies measure the quantity of TSH and not its bioactivity. TSH bioactivity can vary very considerably which is perhaps one reason it is not a good marker for thyroid status, a high TSH indicates primary hypothyroidism but beyond that TSH does not reflect hypothyroid signs and symptoms.

[CL3V3R-G1RL in reply to jimh111]

Makes sense. My last GP freaked when my levels of TSH went down according to him and up my dosage from 25 McG to 50mcg. I didn't understand that. Not would he bother to explain. I had my blood work back in 2019-2020 and it was good. However they were done at different times of the day. Yes he was solely focused on TSH levels. Anyways 2020-2021 I took a test around mid morning and he made changes which I thought it was a knee trigger reaction. My levels were 5.10. And I didn't react well to the 50. Begged him to put me back and he begrudgingly did. My levels adjusted again & I was good until may of 2021. He was concerned cause they were low again 4.75 TSH but this time he would just monitor on it. I got tired of him never wanting to explain things to me and I fired him. He told me there was no way to figure out if I had Hashimoto's. Nor was there anything that could affect TSH levels.

I'm seeing a new GP now and she seems very knowledgeable. 😊

[jimh111 in reply to CL3V3R-G1RL]

That's good. Of course a slightly elevated TSH of around 5 is associated with cardiovascular problems in the long term but you can check things like fT3,fT4 and cholesterol to see you are OK. We each have our own 'set point' so targetting an ideal TSH is not a good idea.

[Hidden]

Isn´t that for your blood sugar and insulin tests? As far as I know, they should be done on an empty stomach, about 12 hours after supper.

[jimh111]

Having a look at your previous posts a year ago it appeared you may be on too much levothyroxine. It would help if you could describe any current signs and symptoms along with any more recent blood test results. There are various reasons it's not good to have a very low TSH although some patients need a low or zero TSH.

[Pinkpetite in reply to jimh111]

This consultant did reduce my dose slightly so that I'm now on 125/150mcg alternate days. Doing gluten free does seem to make my levels better. My T4 was a bit high last time, out of the range slightly, there was no T3 done as it was a different hospital. I'm doing this blood test Tuesday so will see what these results are, this consultant then proposes to discharge me.