I'd ask for the DNA test for MTHFR genetic errors. If you have this you will need special folate too... called methylfolate.

People with this inherited error cannot methylate (activate) B12 and folic acid and become deficient in the face of plenty of the other forms.

Vit D is always good to get tested. 50 is the number to strive for.
RX D2 does not work, so if you need it buy D3 OTC and use 1000IU daily for every 10 points you need to raise.

Some people get B6 tested. If you do stop all fortified foods and vitamins about 3-5 days before the test.

Zinc/copper ratio can be revealing. Some people with poor nutrient absorption get low in these two.

Calcium and magnesium also. But the mag test is only good for very low or very high readings. The in between "normal" is not revealing of need or symptoms.

Some people get B1 done (thiamine)...low thiamine leads to nerve symptoms.