T3 life effect on TSH in blood draw: Will a dose... - Thyroid UK

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T3 life effect on TSH in blood draw

hw7342 profile image
8 Replies

Will a dose of T3 still have a lowering effect on TSH 20-24 hours after taking it? Thank you

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hw7342
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8 Replies
Judithdalston profile image
Judithdalston

Are you hoping to do a blood test to show no signs of T3 dose in your blood ie no raised FT3, nor suppressed TSH...in which no 20-24 hours is not enough. If it’s a private lab test wait till next week.

hw7342 profile image
hw7342 in reply to Judithdalston

You mean go without T3 until next week in order to show non suppressed TSH? Its an NHS one.. so I will be flagged if I get a TSH below 0.35. I self medicate T3 and NHS supply my levo but I think they will decrease it when they see my suppressed TSH. They don't know I self medicate, I have been managing it myself and I usually get private tests done.

Judithdalston profile image
Judithdalston in reply to hw7342

Ok, then much longer to get it out of your system...the wait 6-8 weeks between changing dose and retesting might be ok.

diogenes profile image
diogenesRemembering

Your TSH level doesn't respond as quickly as that. On any dose change it can take weeks or months for TSH values to alter significantly. There's a scientific term for this: hysteresis. This means delayed response up or down in any measurement after a change.

hw7342 profile image
hw7342 in reply to diogenes

Thank you diogenes!

hw7342 profile image
hw7342 in reply to diogenes

Hello sorry to bother you again. Does this mean that taking bloods as early as possible in the day and on an empty stomach to try and show TSH at its highest is a myth?

diogenes profile image
diogenesRemembering in reply to hw7342

No

helvella profile image
helvellaAdministratorThyroid UK in reply to hw7342

TSH changes through the day - highest in the wee small hours, and dropping through to the afternoon/early evening. This is a circadian rhythm which is independent of how high or low the values.

diogenes was talking about the change in TSH from one day to the next, one week to the next, one month to the next which are due to the pituitary reacting to thyroid hormone levels.

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