Does TSH blood test have to be a 'fasting' bloo... - Thyroid UK

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Does TSH blood test have to be a 'fasting' blood test please?

Music1 profile image
23 Replies

Was asked to book another blood test in 4 weeks as they are raising my Levo prescription again. When I went to book bloods I said "as early in the morning as possible please as it's 'fasting'". I was told "no... you should have breakfast first as this can affect your results and maybe that's why your levels are so high". I think I've always been told this was a 'fasting test'. Would food make a difference or ?

Many thanks in advance. Thought I'd ask you all, as you're the experts :)

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SeasideSusie profile image
SeasideSusieRemembering

Music1

Depends which member responds. 99% of responders here will tell you to delay breakfast until after the blood draw.

Check out Diogenes (Dr John Midgeley, advisor to ThyroidUK) reply in this thread, his reply is the 9th one down

healthunlocked.com/thyroidu...

and he says

TSH falls after eating, but FT4 not affected. Don't know about FT3 but suspect it will behave like FT4.

Always advised here is "When booking thyroid tests, always book the very first appointment of the morning and fast overnight (water allowed) . This gives the highest possible TSH which is needed when looking for a diagnosis, an increase in dose or to avoid a reduction. TSH is highest early morning and lowers throughout the day. It can also lower after eating and coffee also affects TSH. Also, take your Levo after the blood draw because if you take it before then your FT4 will reflect this and show higher than what is normally circulating. We usually advise 24 hours between last dose of Levo and blood draw so if you take your Levo in the morning then delay until after the test, or if you take it at night then delay that dose until after the test. These are patient to patient tips which we don't discuss with doctors or phlebotomists.

"

Music1 profile image
Music1 in reply to SeasideSusie

Thanks SeasideSusie. I think I have always fasted. I am desperate for my TSH to go down so I can start IVF. I've always had bloods roughly same time in the morning and they've fluctuated between 2-5. Strangely enough, when I had a TSH test done at 8am it was apparently 10. Whether that was a mistake with the lab, or that the test was done so much earlier in the day I'll never know. I want it to go down, so part of me says "eat something so it will go down", but I also want it to be accurate so ivf will work, or if I get a BFP a pregnancy will last I feel like I should 'fast'. Have had increase from 100mg to 150mg as the increase from 75-100 in 4 weeks didn't make a difference. Thank you for your reply.

SeasideSusie profile image
SeasideSusieRemembering in reply to Music1

Music1

The fact that you have Hashi's complicates things with antibodies fluctuating and messing your levels up.

Music1 profile image
Music1 in reply to SeasideSusie

I had no idea. What a mess. How one thing affects everything else :( Feel like I'm falling apart. Thanks for reply :)

Angel_of_the_North profile image
Angel_of_the_North in reply to Music1

But if it goes down because you ate (and your thyroid hormones are really too low for a successful pregnancy) and you then fail to conceive or miscarry, how would you feel?

Music1 profile image
Music1 in reply to Angel_of_the_North

You're absolutely right. I had no idea that food, or later in the day would make it go down. Whenever, I've seen the locums they haven't mentioned that. As much as I want to start ivf I wouldn't want it to fail or have a miscarriage. I've decided not to eat and have it at 10:30 am, and see if it's gone down just by increasing Levo 50mg. I'll have to pretend I have eaten etc, if they ask. Thanks so much for all your advice.

SeasideSusie profile image
SeasideSusieRemembering in reply to Music1

Music1

It would be best if you can get it done no later than 9am. Check the first graph for TSH levels throughout the day here healthunlocked.com/thyroidu...

I would cancel your 10.30am appointment, say you had something else arranged but had forgotten. Then ask to rebook first thing in the morning another day, just say it's more convenient for you if it's before 9am.

And there's no need to discuss anything about whether you have eaten with the nurse, she's unlikely to ask but if she does just say you didn't feel like breakfast that morning.

Music1 profile image
Music1 in reply to SeasideSusie

That's really interesting. I can't believe I had no idea. Nobody at my ivf clinic, GP surgery or locum etc have ever mentioned any of this. I just end up hearing things like "if you increase Levo your TSH comes done and T4 goes up.... it affects everything'. Oh, and I got told it looks like a butterfly in your throat." I mean seriously. These are professionals that have told me very little/ nothing and all of you on here have been amazing. I've just shown the chart to my other half and he was gobsmacked.

I will take your advice, rebook and try and get a test around 9/ 9:30. Thank you. You're a star :)

humanbean profile image
humanbean in reply to Music1

I've always wondered if doctors discuss the shape of the gallbladder or the pancreas or the spleen or the knee cap or any other internal bits of the body. It always seems to me that 99% of articles on the thyroid start with the phrase "The thyroid is a butterfly-shaped gland in the neck...".

Who cares what bloody shape it is!

Music1 profile image
Music1 in reply to humanbean

Lol. Exactly :)

in reply to SeasideSusie

Yep, don't tell them Music1 ! ;-)

The first time (after reading the advice on here) I nearly did let it out while chatting to the girl taking my blood. I mentioned that I wanted to get this over with as I was longing for a cuppa. She said with surprise "Fasting?" Realised I'd almost blown it I said that I could never eat breakfast first thing in the morning. Thankfully she accepted it. In theory fasting isn't necessary, in practice it's probably the best way to get the treatment we need.

The upper limit of the official TSH range (4.7 if I remember) is far too high, and they don't seem to take it seriously until it goes over 10! So it's best to get tested when the level is likely to be at its highest.

Music1 profile image
Music1 in reply to

That's so funny. I'm the kind of person that would say that. You're both right, thanks for your advise. As much as I want it to go down so I can start this ivf thing I wouldn't want it to result in a miscarriage either. Shame she's put me in for 10:30am. That's quite a long time for me to even go without a coffee :)

in reply to Music1

I wasn't even fibbing, as it takes an hour or so to want breakfast after I get up, only a cup of tea

Lavellekelly profile image
Lavellekelly in reply to SeasideSusie

I take mine about about midnight so should I not take it the night before a blood test

SeasideSusie profile image
SeasideSusieRemembering in reply to Lavellekelly

The recommended time gap is 24 hours. If you normally take yours about midnight, and have your blood test at, say 9am, if you left off your dose the night before it would be 33 hours which is too long and will give a false low FT4. Just for one day why not alter the timing of your Levo and take it around lunchtime/early afternoon, So if you took it at, say, 2pm, had blood test next day at 9am, that would be 19 hours which would be fine. I alter the timing of my thyroid meds when I am doing a test.

Music1 profile image
Music1 in reply to SeasideSusie

That's an interesting thought. Can I get some advice. I have a blood test at 10:30am on Friday 28th. I usually take Levo at 11pm every evening. Normally the night before a test I wouldn't have any. If I take my Levo at 10:30am on Thursday morning (so blood test would be 24hrs apart) would I also take my normal dose at 11pm on Wednesday or will I be overloading the system? Sorry, hope this makes sense?

SeasideSusie profile image
SeasideSusieRemembering in reply to Music1

Music1

Well, some people take their dose once weekly, so you wouldn't overload your system but why not find a window around lunchtime, you can take it 1 hour before lunch. Timing of Levo affects FT4 rather than TSH so as you're looking for an increase in dose I'd concentrate on getting TSH as high as you can so

you really need your appointment no later than 9am.

Music1 profile image
Music1 in reply to SeasideSusie

Thanks for clarifying. Again, I didn't know Levo affects T4 rather than TSH. I want my TSH to go down low enough so I can start ivf asap, but also not affect an ivf result or cause miscarriage later. Do you think Endos at the hospital would take timings/ food and everything else into consideration? The other Endo I saw once seemed really 'laid back' and didn't care too much. Gosh, once a week.... blows my mind. I will take your advice. Thank you so much for writing and advice etc. Best wishes x

SeasideSusie profile image
SeasideSusieRemembering in reply to Music1

Music1

Do you think Endos at the hospital would take timings/ food and everything else into consideration?

No, not at all. There is the very rare specimen that does tend to agree with what we advise (one of the Admin's endos if I remember correctly), but it's generally just not worth discussing as they will ridicule the idea.

TSH to go down low enough so I can start ivf asap, but also not affect an ivf result or cause miscarriage later.

Slightly different from your situation, but I have 4 grandchildren who didn't take breath because my daughter-in-law was undiagnosed, so the plight of hypo patients and miscarriage is very close to my heart, I would hate to think of anyone else going through what she and my son went through and the heartbreak of carrying a tiny white coffin into church :(

So do everything you can to get that high TSH and an increase in Levo to eventually bring down your TSH to where it needs to be to avoid the risk of miscarriage.

Music1 profile image
Music1 in reply to SeasideSusie

Bought tears to my eyes. Such heartbreaking news. I totally get it now. I'm so sorry. I wouldn't want anyone to go through anything that heartbreaking. I don't think I could do it myself. Nobody should have to go through that. <sob>

I will do everything I can now to get a high TSH and keep asking for increase in Levo to bring it down. <tears> I asked about how diligent Endos were at hospital as I was told if I did get pregnant they would monitor things to prevent mc. I kind of think, we have to take responsibility ourselves and not depend on GP or anyone else out there. It's personal experience and wonderful people like yourself and others on this site that I now listen to. So sorry and sad to hear of your daughter-in-law. Hugs. Thank you for sharing. Will totally follow just your advice x

SeasideSusie profile image
SeasideSusieRemembering in reply to Music1

It was a long time ago, she went on to have 3 children, the youngest is 15 now but sadly one of the lost pregnancies was twins :(

Anyway, think positive, you will have lots of support here, there will be others who have been in your situation, so stick with the forum and ask for support and you will get it in shed loads :)

Lavellekelly profile image
Lavellekelly in reply to SeasideSusie

Thanks for the info x

Eating before the test can lower TSH levels, and TSH naturally drops through the day. Since most doctors are TSH obsessed we need to get the highest possible level in a blood test. No point telling/asking doctor or nurse - it's a patent to patient tip. Doctors a0 Don't know much about how thyroid works and b) don't want to spend their practice money on treating you.

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