If you test high --make sure you did not take any vitamins a week before the test.

If you test high and don't take vitamins, then ask for a MMA test.
This will show if the B12 is in the active form and working. MMA should be low in this test to show active B12.

If MMA test is high, then you most likely have the DNA mutation of the MTHFR enzymes which activate cobalamin in the body.

Anyone showing high B12 when vitamins are taken daily, is rather meaningless.... it is an artificial elevation. The ranges were made from people NOT TAKING any vitamins at all.

You are not likely to have high B12 from food, as there is not enough to elevate it ... unless the food or energy drink is heavily fortified.

High B12 with no supplements, indicates several disease states potentially present. Some cancers of the blood, some liver disease, kidney disease, intestinal overgrowth of unwanted organisms, sometimes present as high serum B12. High levels of inactive B12 indicate the MTHFR mutation. The tests measure all forms of B12 and not just the methyl form.

Excess B12 in the serum will be eliminated by the kidneys (unless they are damaged and not working well).
High levels only indicate disease in the body, but the B12 itself is not toxic. For those with the rare condition called polycythemia vera, excess B12 may contribute to the red blood cell elevation. But this is evident in the CBC testing.