Hello. I am on T3 only (no thyroid) and organising blood tests. Is it correct to take blood 4 hours after the early morning T3 dose ?

[Trakehner]

I'm new here... any advice on the timing of blood tests for those on T3 only?

[Lalatoot]

It depends on whether you want to measure the peak or the trough.If you have bloods 4 hours after a dose you will measure FT3 at a peak. If you take bloods 8 - 12 hours after a dose you will measure FT3 in a trough.

[Trakehner in reply to Lalatoot]

Thank you very much for you reply.

Without going into detail, I have had problems getting a stable T3 dose for years. I've been told to measure my FT3 levels 4 hours after a morning T3 dose and then when my FT3 levels were elevated and my TSH raised, was told I was on too much T3.

In order to see whether I am on the right dose regime, do I need to get tested at 4 hrs after a morning dose and 8-12 hours after an evening dose to establish FT3 peaks and troughs? Presumably on the correct dose, my TSH should be very low or suppressed at both times and my FT3 levels if taken on average should not go beyond the top of the FT3 range?