Test preparation

[Mickeydooley]

I know I’ve asked before and I’ve read all the advice regarding testing etc but I’m still a bit confused. I’m having blood tests done tomorrow morning (8.40am) and will be fasted and have taken my last dose of levo this morning. I also take metavive daily and have been advised to take the last dose 8-12 hours prior to test. Since I usually take my levo and metavive together in the morning why would I give myself an extra dose tonight before the tests? It’s not what I usually do and surely it will raise my levels? Or maybe I shouldn’t have taken them this morning? Your advice would be appreciated.

[MaisieGray]

No, when that suggestion is being made, you aren't required to take a second dose; but to to adjust the time today, of your dose, so that the gap between taking it and having blood drawn, is 8 - 12 hrs.

[Mickeydooley in reply to MaisieGray]

Oh dear! I misunderstood! Doh! I took the metavive this morning with my levo. I assume it would be best now not to take any more before my tests tomorrow?

[SeasideSusie Remembering in reply to Mickeydooley]

No, you've taken your thyroid hormone replacement dose for today, don't take any more.

However, due to taking your Metavive this morning, if there is any T3 in it (and they don't disclose any hormone content) then you will get a false low FT3 result from your test. This is why, when taking T3, NDT or Metavive (hoping it contains some T3) that the last dose is 8-12 hours before the blood draw. Any close to the blood draw and the FT3 result will show a false high, any longer and it will show a false low.

So If your test is including FT3 and you want that to be accurate, tomorrow's test wont be any good. If it's important to have an FT3 result, cancel the appointment and rearrange it for a few days time and get the timing right of your thyroid hormone replacement, i.e last dose of Levo 24 hours before tet, last dose of T3, NDT or Metavive is 8-12 hours before test even if it means altering the timing of your doses the day before.

[Mickeydooley in reply to SeasideSusie]

Thanks for your reply. I wasn’t thinking this morning and just took everything. My t3 is already fairly low and I’m visiting an endo next week to discuss. Unfortunately I can’t get another appointment for bloods in time for this meeting.

[Mickeydooley in reply to SeasideSusie]

Didn’t need to worry about the T3 being low! Got results yesterday and after asking specifically for T3 and antibodies to be done they weren’t! I got 8 pages of test results including admission profile and FBC but only TSH and T4 tested! Ah well! Was obviously hoping for too much! Will be interesting to see what endo says on Monday. Will take my medichecks results with me although I know he won’t look at them. The endo isn’t a thyroid specialist anyway.