What's the best way to get an accurate TSH reading?

Hi, I'm diagnosed subclinical hypothyroid and for reasons too complicated to go into here my last blood tests showed 'normal' TSH and FT4. I don't believe they were accurate and I want to get my doc to retest them. I've never done anything special to guarantee accuracy but I know that there is an optimum way of doing them, I'm just not exactly sure what it is!

So, what is the best way of getting an accurate blood test result for the two conventional NHS tests? I rise at 10 am (I think they're supposed to be done not long after rising?) so I'd be grateful for any advice on how to arrange my blood test appointment to get the best out of it. Thanks!

30 Replies

  • Chancery, TSH levels fluctuate according to circadian rhythms. They're always 'accurate' but TSH is highest early in the morning and drops after eating and drinking anything but water, which is why members looking for a diagnosis or dose increase are advised to have an early fasting test.

    Have a look at the graph in this link healthunlocked.com/thyroidu...

  • Thanks, Clutter. Really, it seems, looking through the graphs, that it makes no real difference when you have it taken, if you are up and about at the hours I am. Certainly mine have been all over the place, time-wise, between 2PM and 5 mostly, with only one in the morning, and it wasn't much different from the others - certainly not higher. I would have thought, also, that your own circadian rhythms could be slightly different from a mean average. I will, however, go without breakfast this time and see if that makes any difference, other than me potentially fainting, that is!

  • Chancery, it may be worth getting the earliest appointment available which can make the difference between being over range in the morning and considerably under range later in the day.

    I schedule my blood draw around 2-3pm because TSH is lower then and I don't want endo reducing dose because TSH is over suppressed.

  • My FT4 always seems to be about the same - on the low side. It was my TSH that had plummeted from 5.2 to 1.9. Wouldn't it make sense to follow your lead and have an afternoon appointment, which I usually have, so that my TSH will have elevated (if it's going to)?

  • Chancery, no, I just edited my post, TSH is LOWER mid afternoon, so my cunning plan is flawed.

    To get a diagnosis you need TSH at it's highest which is around 2am but phlebotomy ain't open then so it's the earliest blood draw you can arrange.

  • Ah, that makes more sense! Right-ho, I will drag myself out of bed at the earliest hour then, and forgo the Oatibix. Ta!

  • Take something with you to eat straight after the blood test. I usually take a banana and maybe a bottle of water. MariLiz

  • Good advice, Mariliz, thanks. I'm not a fainter, but there's always a first time. Banana it is....

  • Hi Chancery, Try to get up early on the morning of your blood test and then your TSH may be back up to around 5. There is a real difference between early morning and afternoon test results.

  • I'm going to try, Muffy. I'm going to ask for a phlebotomist appointment, rather than my doc. She only works mornings, so hopefully I should be able to get some indecently early hour (can't believe I'm actually WISHING for an early appointment - I hate them!)

  • Could well be worth the effort, even if difficult for you. At least that would be a start for you. Good luck.

  • Thanks! X

  • The more important tests is the free t3 . I would see if you can get that or order yourself.

  • I have had it done once before, Faith, but my doc freely admitted he had no idea what it meant or what the results meant. He knows how to interpret the standard tests - no point in trying to motivate him with anything fancier!

  • Many take their health into their own hands. Getting testing without a referral and self treating. Doctor don't seem to know how to treat this at all.

  • I don't blame them. At the moment I'm just keeping my stats under a watchful eye; I'm not in a hurry to be treated, but I do want to know what's going on. I'm happy to rely on the TSH testing. I just want to make sure I get the most accurate reading so that if there is a problem it isn't being casually dismissed. My doctor's big on dismissing!

  • TSH testing is not accurate and is a Pituitary Hormone, not a Thyroid Hormone. My Pituitary reading is suppressed from Thyroid meds and a doctor would lower my thyroid meds based on that alone, if that's all they look at. Yet, i am not overmedicated, in fact, full of hypo symptoms. It is just not accurate or a good look at the full picture.

    If you are hypothyroid with symptoms, you should be in a hurry to start treatment. Especially if you have Hashimotos.

  • Unfortunately, Faith, there's a few things that could be causing me problems, so it's not possible to be sure what's hypothyroid and what isn't. I'm on Carbamazepine which, depending on who you read, either disrupts thyroid or just gives dodgy readings in blood tests. It was my hope that I would be able to get off the drugs and so get a better picture of the thyroid, but I'm stuck on 300mg of the drug, so that won't be possible. That's why I want a retest, because I'm not sure what role having the drug removed (in hospital) played on my last blood test, since the two things were close together.

    So, for now, I just want to keep a weather eye on it and see what it does. If I'm stuck on the drug and the hypothyroid readings keep coming in, then I think I might have to do something about it, but one step at a time!

  • Why are you on Carbamazepine ?

  • For trigeminal neuralgia.

  • I wanted you to know that Hypothyroidism can cause Nerve pain and Neuropathies, Joint and muscle pain and Osteoporosis too. There could be a connection between Hypo and this pain. No doctor will know this and you would have to do your own research.

  • Yes, I was told that recently by someone on here (not you, I hope; I have real brain fugue tonight!). I have looked into it a bit but it's limited because TN is a rare disease and they don't tend to look for causes, more for drug treatments, as it is considered incurable.

    But I am on that, yes. It's one of the reasons why I want to watch my thyroid figures; I'm not convinced that they are normal, and I'm not convinced they are not playing a (causative) part. I believe it's particularly true if hypothyroidism is left untreated for a long time, so yes, I reckon that might well apply to me. But thanks for the tip anyway; it's always reassuring when more than one person says the same thing!

  • I hope you are able to look into all of it further.

    Be aware that, again..i can't emphasize enough!!!..that, the TSH is not enough!! That people with thyroid hormone resistance, can have a normal thyroid panel yet are very hypothyroid. A really good thyroid panel is a ft4, ft3, reverse t3 and thyroid antibodies. Until you have those done, you really don't know that you are ok. The number you are watching is not going to give you an answer.

    Here is a list of symptoms that could indicate thyroid:


    Since the most common cause of Hypo is Hashimotos Disease, i have included this..this story about my life..lol!!


    I hope you pursue it.

  • Yep, got most of those symptoms, Faith. But my doc always says, probably quite rightly, in fairness, that those symptoms are so common and generic they could mean anything or nothing. I was tested for antibodies and found wanting. Nary an antibody in sight, so it's not Hashimoto's.

    I actually got results of an ANA test today, also negative. I think I've been tested for every autoimmune thing going, including coeliac and parietal cell antibodies and IF and all of it has been nil. I am the least autoimmune person on the planet, I think!

    I am reduced to thinking it is either non-coeliac gluten sensitivity, chronic inflammation or hypothyroidism. They are the only things left with any credibility, but my body isn't playing along. I am the most healthy unhealthy person I know!

    I shall keep going and hope that some day something will give me a clue as to what is actually going on with me. Trouble is with doing that, it can often be something disastrous that strikes and by then it's too late. But I don't know what else to do. My doc won't test for anything and I'm running out of ideas.

    Thanks for all your help.

    P.S. Is that your actual Facebook page, or does it just mirror your own story?

  • I guess you can believe your doctor and stay ill.

    You have had thyroid antibodies testing then? And they are both negative? I am sorry if you told me and i have forgotten. Normally if you have symptoms and they can't find anything, it is autoimmune. Food can make people quite ill too. Autoimmune and food sensitivities go hand in hand.

    No..it just Mirrors my life.

  • Hi Faith. Yeah, I had one set of antibodies tested - I think it's TPO? They were 3.5 - so low it's an insult to antibodies! I really do seem to be autoimmune free, unless they are being VERY cunning and hiding in plain sight somehow.

    Whatever is wrong with me, I don't think it's that, even although it FEELS like it is.

  • TSH has a distinct circadian rhythm which can fluctuate around 70-80% on the same day! There are other influences such as whether or not you have fasted, if you are sleep deprived and whether or not you are male or female. There are even seasonal fluctuations! Sleep deprivation can also increase your TSH. My advice to you is to have the test as early as you can in the morning and to fast at least 10 hours before you have the test. I have done this with considerable success. My GP sent me for a test (2.pm) and the result was TSH 2.5. Three weeks later an endo I was referred to, sent me for another TSH test. I went to the lab as hungry as hell at 7am with a TSH 4.2 result. The lab where I live has a TSH reference range 0.4 to 4.0

  • Thanks, Mongolia. I am quite prepared now to go in at some ungodly hour of the morning, starving like a wolf. I shall expect my TSH to be through the roof, or I'll want to know the reason why!

  • Fingers crossed and good luck!

  • Thanks!

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