Thyroid UK
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when to have labs on NDT/question about FT3 levels?

OK, sorry if this question has just been asked before. But I have been wondering about something lately; namely, what your FT3 levels should look like when you go to the lab, if you follow the advice to go there 24 hours after taking NDT. Because, if FT3 levels are at the top range or even slightly out-of-range 24 h after taking NDT, does that not mean that they were more or less twice as high the day before; that is, just after taking NDT...?

My lab has uses reference ranges of 1.8-3.8 for FT3. On 5 grains of Armour (I had labs 24 h after taking any meds), my FT3 levels were 2.9, and my doctor concluded that Armour was not working for me.

One thing that is interesting, and that my doctor commented on, was that my FT3 levels looked exactly the same when I was on T4 drugs only.

So, to sum up, twenty-four hours after taking 5 grains of Armour, my FT3 levels were mid-range.

So, in a situation like that, what is it advisable to do? Raise Armour until FT3 levels look like...what? Or go to the lab right after taking NDT, rather than waiting 24 hours...?

2 Replies

thecat, dose should be increased to relieve symptoms not to target lab values. Ideally FT3 will remain within range rather than over. I explained why thyroid replacement should not be taken prior to testing and how to estimate normal circulating FT3 in the link below.




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