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first test fasting, second test not? could this make a difference?
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first test fasting, second test not? could this make a difference?

I recently was diagnosed by my gynecologist as having hypothyroid.  On the first test I was fasting for a blood sugar test and my thyroid results were TSH 5.65, T4 10.2, T3 19 (not sure what kind of test the T3 was said normal range was 24-39?).  They put me on 25mcg Synthroid (I have MVP and doctors were worried it would make me jittery to go higher).  I just went back last week and the tests come back with TSH 1.5 and T4 9.9 - they didnt do T3 this time because it was an in-house test and they dont do that one.  What I want to know is, if possibly because I was fasting the first time, my test results were skewed.  It just seems odd to me that such a low dose brought my TSH down so much.  I wonder if some how fasting drove my TSH up and I'm not really hypothyroid?
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154 Comments Post a Comment
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231441 tn?1333896366
hi,

fasting has no impact on results. Yes, such a low dose could normalise your results. regular monitoring will still be required.


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Avatar n tn
Ok, thanks, I'm new to this and figured that was just wishful thinking!
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Avatar m tn
you should fast for 14 hours before the blood test, and drinking too much water !
the result when fasting is the true one !
175 mcg/week is not too low dose ,it's an initial dose !
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168348 tn?1379360675
I think she is on 25mcg's not 175mcg/week ?
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Avatar m tn
what is the difference between 25 mcg/day and 175 mcg/week ??
the correct way is to say per week  !
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168348 tn?1379360675
OH .. my apologies .. you are so correct .. they are one in the same.  I misread the orig. post as 175mcg's per day ... I guess I got so worried for the member's health on that dosing that I missed you calculated the daily into a weekly dose :)

Sorry -

C~
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168348 tn?1379360675
That leads me to the post above .. if I fast but do NOT take my Synthroid that morning before my bloodwork will that affect my TSH results.  I've been on Synthroid for 2.5ysr and at this particular dose for 6 weeks.  Thought you may know .. thanks

C~
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Avatar m tn
when I do blood tests I always fast and don't take the med that morning but after the blood test !!

feel well !
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Avatar f tn
I also fast before labs and have them done at roughly 8.30-9am every time.
Consistancy is the key and yes...fasting and not fasting can give an inconsistant result.
So always fast before labs.
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Avatar n tn
Thanks for the input everyone!  I am also concerned because I am still having nervousness, would this be because my dose is low or high or what?
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