I know we are supposed to get bloods done around 9am, empty stomach and 24 hours since last dose of thyroxine.
However what happens if I’ve had a disrupted night’s sleep. Woke at 5am, tossed and turned for some time, went back to sleep and then had the test done at 9am. Can this dramatically skew the results? Are TSH, T3 and T4 that sensitive?
It is personal choice. Many get bloods done early as it makes a small difference to TSH and this is important when the GP is dosing by TSH.
My surgery does not do early bloods for thyroid so I get mine done at 2pm. I keep the time consistent.
My TSH is suppressed and will always be so that discussion has long gone. I take my last dose of levo 24 hours before hand and my last dose of lio at 6am.
Dk123
I don't sleep well and I'm up 2 or 3 times at night for the bathroom. Sometimes I don't get back to sleep properly but maybe just drift. But I always do my home tests around 8.30-8.40am and my GP tests as early as they can give me. TSH doesn't matter for me as it's always suppressed anyway, but I haven't noticed any difference in my FT4/FT3 regardless of how my sleep has been the night before the test.
Ok thanks for sharing, keen to see a few more responses before I post up my recent blood tests results.
I f you 're just talking about one night of disrupted sleep . i doubt it would affect TSH .
The high point (if you still have much of one on levo) has already happened in the very late evening /early morning and it's downhill from there, so i would have thought that day's TSH should still be whatever it was going to be, however early you woke up .
I do wonder of long term altered sleep pattern (like permanent night shift) may have an effect but haven't seen any studies on this.
I have read that the peak in TSH is often blunted once we are taking thyroid hormone replacement, and even in healthy people not everyone has a big range between highest and lowest TSH.
As far as i know FT4 and FT3 have more to do with time of dose than time of day. The only reason early morning tests are advised here is to get the highest possible TSH .
Where did those ‘supposed to get’ come from.... where’s the rationale.... I’m asking the universe here.....
The most important thing is consistent timing for every test so results can be compared over time and that the test reflects actual usual steady state thyroid function i.e. no perturbation from changes to dose regime just to facilitate a test...
I suspect part of the problem is the unphysiological practice of taking all the levothyroxine in one dose on waking which floods the body with excess free t4 before it equilibrates over many many hours - the functional thyroid system doesn’t do that, it drip feeds in more or less even pulses over each 24 hr period. So if we have to avoid testing within 24 hrs it kind of indicated we shouldn’t be taking it all at once if it could skew our blood levels so much....
I like to know what my highest tsh and lowest thyroid levels are and to be totally in control of the time of test for consistency and comparability, so I test at home late in the evening just before my next thyroid replacement dose which I split into 4 over 24 hrs, in other words There is a 5-6 hr gap between last dose and blood draw and that last dose would be only 1/4 of the total for the 24HRS. In this way I get to see the actual effect of my thyroid replacement without any change to ‘accommodate’ a test and there is no concern about unphysiological or unusual peaks or troughs.
Some people seem to stop their levothyroxine for 24HRS in case it helps show a higher tsh if the want to convince a doctor to prescribe more thyroid! That really is madness. The thyroid system is highly sensitive to disruptions and adverse effects seem to come from the body trying to find a balance from the unnatural feeding regime of thyroid hormones compared to the balanced demand and supply of a healthy system.
Timings for thyroid blood test
Blood tests - time taken 
Timing of blood tests
