Dr. Fung recommends eating your normal diet for 3-5 days following an extended fast, then fasting for 12-14 hours (or whatever was ordered) for your bloodwork, otherwise your lipid panel can be skewed.
I think that for the things you listed, there would be no problem even if you still fasting as they had the blood colected. The turnover rate for red blood cells is at least a month, your body is very efficient with vitamin B12, to the point that even in EV reposition therapys we have to wait a little to see results, the only one i am not so sure is the T3 and T4 count.
Fasting won’t affect these values, except maybe the b vitamins.
Thyroid, RBCs won’t change much unless your fast is crazy long. Maybe not even then. Lipids and glucose require at least 12 hours fasting when measured anyways. During longer fasts they stabilize to early fasting values.
As someone mentioned though, you will have ketones in your bloodbath urine. If they are testing for that, it will show up.