From the recommended timing protocol in the sticky posts
T3 has a shorter half life and many split dose to reduce chance of early onset and prolong its action. The last dose should be taken between 8 - 12 hours before the blood draw. Those who don't split dose are recommended to do so the day before the blood draw.
I am confused by this. If I normally take 15mcg in one dose in the morning but the day before testing I split my dose and take 10mcg 8-12 hours before testing the result will show the median level of serum T3 based on only 10mcg and not representing my full dose. So how is that useful?
If I wait to take the whole dose until 7-8pm I'll have an awful day
I felt grumpy about this and decided to take as normal and test on the same timeline as my T4 but fully accept that the results are useless because serum T3 is down to baseline. I'm going to have to do it again.
Can anyone comment please on the utility of taking only a portion of the dose within the desired 8-12 hour window or shall defer the whole 15mcg to 12 hours prior to test and chose to have an awful day the day before testing?
Many thanks
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Pearlteapot
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Pearl, you devise your own testing protocol that suits you and you interpret your results accordingly. Nothing is written in stoneIf you don't want to measure ft4 and ft3 at their highest then do not test 2 to 4 hours after doses.
If you want to measure ft4 and ft3 at their lowest then count the number of hours between your doses and leave the same number of hours between your dose and blood test
If you want an average level of ft4 and ft3 then leave a gap of half that number of hours .
Then interpret your results accordingly such as this is the lowest my ft4 gets or this is the average level.....
Fasting and first thing testing is done to get the highest TSH. But if you don't focus on TSH then test when you want and no need to fast. This allows you to time your tests to make minimum changes to your dosing . Take your full dose as per usual and take a blood test 8 to 12 hours later and you will have the average levels. Take your doses as usual and test 24 hours later and you will have your lowest levels.
What you do is up to you as long as you decide what your doing and then do it each time to compare like for like and as long as you understand the implications of the gap you leave giving you lowest, average or highest levels.
Thanks slowdragon, but if I do that the first 2 x 5mcg doses will already be at base line by 8am the next morning and only the final 5mcg 9pm dose will be reflected in my serum, that's the bit that I don't understand about it. Sorry if I'm being dense.
if was taking T3 ( i'm not) , i'd want to know the peak 4 hrs after my usual dose (for myself only, not the Doctor)
i'd also want to know the mid point 8-12 hrs after my usual dose ,
So i'd do two tests privately at 'whatever time of day' to fit with whenever i usually took my dose (knowing i could ignore those TSH results , so time of day of testing is not very important)
Then i'd have full information about my usual fT3 levels for my own purposes . i'd know if my fT3 ever spiked horribly over range or not .. and i'd decide on how to test routinely for GP/Endo based on that knowledge .
Testing T4 / T3 Is not a "right answer / wrong answer" situation, the timings we use to test Levo or T3 depends entirely on what information we want to know , and on who is going to be seeing it....... is it someone using their intelligence , or is is someone with their hands tied by guidelines (or ignorance) who has the power to screw up your quality of life if they fiddle with your dose when yo feel well. .
i too have always had a bit of a "?" about the utility of testing 8 -12 hrs after taking 5 mcg if the usual daily dose is more like 30 mcg taken in one go in the morning . .
But what ever you decide to do re GP/ Endo testing . you need to find something that can be done consistently so you can see any changes in your levels , and that doesn't leave you unable to function for the day
Thanks so much tattybogle - that has switched on a light for me. Yes this is for me, not for Endo. And you're so right, I don't have to arrange my dose timing around a morning test if I'm not testing for TSH although I suppose I'll get false highs for T4 if testing after 8 hours after dose. I'd got all fixated on 9am fasted testing but that is entirely driven by TSH. Brilliant, thanks.
Yes, once I see the outcomes I'll settle on a consistent system for Endo. Suspect it will mean taking T4 in the morning and full T3 dose at bedtime for a 8am test and having a bit of a bad day.
I take 50mcg levo and 5mcg lio at 6am and 50mcg levo and 2.5mcg lio T3 at 10pm. So approx a 16 hour gap and an 8 hour gap between doses. It suits me!
I always have a blood test around 2pm. I take my lio T3 as normal that morning - that gives me an 8 hour gap between dose and testing (half the 16 hours) so I consider that an average level for ft3 result. I don't take my levo till after the test so a 16 hour gap for levo - I consider the result as the lowest level my ft4 gets to.
I fell into the routine by accident as my surgery don't do early morning blood tests for thyroid. But I'm happy with it as it means minimum disruption to my dosing and I am happy with the interpretation I put on the results.
that makes sense although half your Lio is 16 hours ago and will be back at base line so your test only reflects the morning dose. Unavoidable for splitters though.
But is is the reality that my body has every day. And at around 2pm every day that's what my level will be because I haven't changed any dose timings.I would do the same for my levo dose and take it as normal too but historically before I added lio I didn't take it before a test so I have just stuck to that t4 protocol.
when talking about 'base lines' and 'only measuring the morning dose' ,....you have to bear i mind that taking one large dose of T3 ( or T4) is highly unphysiological...... the ref ranges for fT3 (and fT4) are derived from 'healthy' people who have a constant drip feed supply of T3 from their thyroid over the course of the day ... so testing 8 hrs after a full dose is not more or less accurate than testing 8 hrs after half the dose .. they are both equally 'wrong' as neither of them bears any real relation to the ref range which was made from measuring the very steady state of fT3 that results from a small but constant T3 dribble from the thyroid ,plus the T3 that is constantly converted from T4
Splitting T3 into 2 or 3 smaller doses and testing 8 hrs after half or third of the total daily dose is actually much closer to 'reality' as far as comparing that result with ref ranges is concerned. (and is also much closer to physiological normality)
if you feel ok without needing to faff about splitting T3 everyday, then that's great make life easier as far as daily routine goes .. but it makes interpreting your fT3 level in relation to the ref range LESS close to the conditions under which that ref range was actually created.
hmmmm. I did find with splitting that I had many dips whereas I stayed steady on a single hit. But maybe I’ll give splitting another go. I haven’t been willing to experiment while I was seeing endo regularly but I’m not seeing him till end of August now and I’m pretty much on my optimum dose so I’ve got some wriggle room to play around with timings. Oh for a steady drip drip drip.
i've got one of those 'accidental' routine's too . i take 50mcg Levo a.m /62.5mcg bedtime. i always book tests at about lunchtime , fast until test and delay that mornings dose until after the test...... giving about 12 hrs from last dose levo.
lunchtime gives a good comparison with all my years of previous tests before i knew about TSH circadian rhythm, so i carried on doing it even once i realised TSH would be near lowest at that time ..... and i'm happy that 12 hrs post dose is going to be 'near as dammit' back at base line for fT4........... plus if GP gives me any gip about TSH i can always pull the "but it was tested at lowest point in the day" out of my hat ....and i'm long past the "but your TSH is low so you'll die" conversation with my GP so i don't mind if he sees the lowest anyway., he can have another row about it if he wants, but i'm not changing my dose unless i want to .
mainly for consistency .. so i know that no other 'variable' else has affected my TSH result apart from my circadian rhythm , and so it's simple to repeat exact same conditions at all future tests.. without having to remember what (if anything) i had for breakfast a year ago.
( i don't find it a problem to miss breakfast occasionally , so it's not a big deal for me ... if it was difficult to manage without food till lunchtime , i wouldn't bother fasting)
And partly because i know 'breakfast' can lower TSH by up to 30% in some people.... which i appreciate is cock-eyed logic since i'm deliberately testing pretty near the lowest point anyway.. but i suppose i don't want it to be any lower than it has to be .. if that makes any sense at all ,lol
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No it's not to preserve empty stomach for absorption .. on testing days i let myself off my 'wait an hour before food' rule .....i always... walk up to test / get test / swallow levo / go in pie shop over the road from the docs / buy pie / walk home down beach while eating pie .
Because i split my levo half am/ half bedtime it's not such a big deal if i mess up the absorption of one the halves by eating pie with it .. and i could add another 12.5mcg to bedtime dose to compensate for any loss of absorption if i wanted .
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