| Re: question on bloodwork
There are two ways T3 appears in the bloodstream. A portion of it is bound up in a protein that must be stripped off before the T3 can be absorbed by the cells. The other portion is "free", and readily usable by the cells. There is no way to know how much is bound and unusable if only the total T3 is measured. That's why it's preferable and more informative to measure only the free T3.
T3 uptake actually has nothing at all to do with the amount of T3 in the blood.
If there's an "other" blank at the bottom of the lab requisition form, fill in free T3. It's still possible that the lab in question doesn't even run the test, but it's worth a try.
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