Why Low T4 but good FT4 result?

[NWA6]

Just looking for some insight/educating on low T4 but good FT4 result.

T4 62.6 (66-300)

FT4 17.4 (12-22)

I am on combo treatment so I think it’s really good that I’ve got a good FT4 result.

[greygoose]

T4 is actually called Total T4. There are two types of T4: bound and Free. Total T4 is the total of all the T4 you have in your blood - bound and Free. And, the problem is the test doesn't tell you how much of each. Bound T4 cannot be used by the body, so it's logical to want to know how much Free you have available for use.

I don't know for sure, but I would imagine that the answer to your question is that you have more Free T4 than bound T4, so the total is under the range. But, you obviously have quite a bit of FT4, so that's alright.

[Digger031145]

So what is your ft3?

[NWA6 in reply to Digger031145]

6.58 (3.1-6.8)

[Digger031145 in reply to NWA6]

What dose of t4 and T3 are you on and how long after your last dose was your blood draw?

[NWA6 in reply to Digger031145]

All good 130396, I’m quite clued up on blood tests and what’s what. I’m just looking for specific info here about low T4 but good FT4 🤗