My b12 has been 150-190 for 4 years now. my other labs are normal, negative for pernicious anemia, no symptoms that imply ibd, negative for celiac, and no other cause found. no real symptoms but folate is a bit high. should i just supplement?

B12 deficiency can be treated by over-the-counter, oral B12, supplements, ask your pharmacist about these. B12 deficiency should have a valuation and diagnosis by primary care physician.

Your B-12 levels are far too low and need to be supplemented. Would not be surprised if you have at this point early neurological complications. Initially, at least, I would recommend starting monthly B-12 injections and later going to oral or sublingual preparations.