Are there nationally set set parameters for minimum and maximum levels of T4, T3, and TSH,, or does each Health trust's lab set its own?

[HilaryB]

[helvella Administrator Thyroid UK]

The reference ranges are related to the lab and the testing technology they use. Quite possibly every single lab in the country has at least slightly different ranges.

I do not know how labs fit to trust boundaries - but it seems likely that at least some labs will do work for more than one trust, and some trusts might even have more than one lab. So I doubt whether trust boundaries are the defining aspect.

Rod