Best time to test for T3 please?

[TaraJR]

My GP took me off my 150/175 Levo 3 weeks ago, and I am now on 40mcg T3 daily. I'm due a blood test on Thursday. Is there a best way to do that? Eg test early morning / no food or meds beforehand? I know that applies when on Levo, but don't know what's best when on T3 only. Thanks in advance

[Starfish123]

Hi,

I have heard with regards to T3 to test in the morning as early as possible but not to have taken any T3 for 24 hours before test as not to skew results.

I'm not on T3, hopefully if something is wrong with the above someone more knowledgeable will be along to correct me.

Hope it helps

[jimh111]

I take L-T3 at breakfast and bedtime. If I have a blood test I take the bedtime dose and have the blood taken in the morning before taking the morning dose. If you have the blood drawn within hours of ingesting the L-T3 it may give spurious results. If you leave it too long then it is difficult to factor in the half-life.

When I get my fT3 result I add on about 10% to get a rough idea of what the average daily level is. If you wait 24 hours you don't really know if your T3 half life is 24 or 48 hours or whatever. In which case you can't really calculate how much you should upscale the result to get the true figure. I'd have the blood taken reasonably soon but at least three hours after ingestion.

[Angel_of_the_North]

Early am, same as when on levo. Don't take T3 for about 12 hours before hand. That's a big drop in meds - do you feel OK?

[greygoose]

Are they testing the FT3? Because TSH and FT4 won't tell you anything when you're on T3 only. They will both be low - TSH possibly suppressed. I hope your doctor knows that.