When to take test?

[Tuxi1]

Quick question - what time of day is it best to take a thyroid test?

[SeasideSusie Remembering]

Tuxi1

We generally advise no later than 9am. This is because TSH is highest early morning and lowers throughout the day.

As most doctors only look at TSH (which is a pituitary hormone) rather than the actual thyroid hormones - FT4 and FT3 - then if we are looking for an increase in dose or to avoid a reduction then we need TSH to be as high as possible.

However, your previous posts suggest that you are taking T3 only, in which case TSH is going to be very low or suppressed (and FT4 low), and when taking T3 only the only relevant result is FT3.

[Tuxi1 in reply to SeasideSusie]

Hi - Yes, I am on T3 only. I have to go to the hospital at 9am to have it done and there is usually an hour wait! will that be ok? Just got to get those timings right for the day before taking the T3! Got to get sorted! Thank you

[SeasideSusie Remembering in reply to Tuxi1]

As I said, early morning test is to give highest TSH when that is used to adjust dose. Your TSH is going to be very low anyway so it's irrelevant and FT3 test is the most important so the hour's wait wont make any difference.

Timing for your T3 the day before is to split your dose into 2 or 3, whatever is most suitable for you and the dose you take. Take the last portion of your dose between 9pm the night before the test and 1am, this gives the 8-12 hour gap.

[Tuxi1 in reply to SeasideSusie]

Ok - That's helpful - Hope I can find some answers with this being tested!

[Lalatoot]

It depends on the result you want. If your doctor is fixated on TSH for dosing then you need an early morning test - before 9am ideally as TSH is slightly higher then than it is the rest of the day.If you are on levo and lio your TSH is likely to be supressed anyway. If your doctor is okay with this and does not dose by TSH then you can take your blood test when you wish. As long as you follow the same routine every time so you can compare like for like.

I always have a blood test at around 2pm. My doctor access my non-existent TSH. 2pm allows me to take my lio in the morning as usual around 6am.