Are elevated b12 and folate (folic acid) levels bad? cause of this? how to bring them down to normal levels?

No : Not bad. Usually caused by vitamin supplementation. No need to bring them down.

Needs evaluation: High B12 & folate (folic acid) is not dangerous per se (these vits. Have no known toxicity)& may not be serious, but high B12 may paradoxically be a sign of B12 deficiency & may also be caused by acute or chronic liver disease or leukemia, so deserves further evaluation-see http://healthyeating.Sfgate.Com/high-vitamin-b12-serum-levels-6037.Html high folate (folic acid) may be a sign of B12 deficiency or blind loop syndrome.