B12 is not in a standard chem screening panel.

It has to be requested separately.

Doctors have various agreements with various lab facilities.
The term fatigue labs is easier to write out than the various tests for fatigue separately. It is like using speed dial on your phone.

I have never heard of "fatigue labs"...so that may be unique to that particular doctor or lab setting.

Thanks for the info. What's are the relevant blood tests to ask for? Do they do hormone screening as well, or would you have to see an endocrinologist for that?

Many GPs order hormone tests, thyroid tests, etc. Interpreting them however, may be good or poor, depending on the education of the doctor.

The B12 test is often poorly interpreted, with really low values still being called "normal". Many doctors still don't know that 400pg/ml is now considered the new acceptable low.