TSH and T3

[Soozysoosop]

Hi all

I am on liothyronine and levothyroxine. Have I read somewhere on this site that TSH is unreliable when on lio? Mine is always low so I tend to go on t3 and t4 levels

Thanks

[SlowDragon Administrator]

Correct, TSH is almost always suppressed on any dose of T3

Essential to test Ft4 and Ft3 plus vitamin D, folate, ferritin and B12

If taking any supplements that contain biotin remember to stop taking a week before ALL blood tests as biotin can falsely affect test results

Recommended on here that all thyroid blood tests should ideally be done as early as possible in morning and before eating or drinking anything other than water .

Last dose of Levothyroxine 24 hours prior to blood test. (taking delayed dose immediately after blood draw).

This gives highest TSH, lowest FT4 and most consistent results. (Patient to patient tip, best not mentioned to GP or phlebotomist)

If/when also on T3, make sure to take last third or half of daily dose 8-12 hours prior to test, even if this means adjusting time or splitting of dose day before test

[Soozysoosop in reply to SlowDragon]

Many thanks