Re: Phentermine and thyroid blood test
I don't know about the phentermine question. But TSH of 3.88 is still too high anyway. That kind of fast flux can happen with the most common cause of hypothyroidism - Hashimoto's thyroiditis. That could be what's going on.
It might be acceptable to sit and wait until your iron level is better, because that can cause mild hypoT. But I still think you're going to need thyroid replacement sooner than later.
"We can complain because rose bushes have thorns, or rejoice because thorn bushes have roses." Abraham Lincoln