Since B-12 is water soluble, no number is really "too high" because you will urinate out whatever your body will not use. The goal, I would say, is to keep your B-12 levels above 1000 when shown through blood work. I also recommend trying lipo shots vs straight B-12 (meth or cyan) since they also encompass essential amino acids to help with muscle growth, fat metabolism, and energy production in cells. Lipovimino has been personally working wonders for me. For more information, check out this website: http://www.agemanagementoptimalwellness.com/injectablesupplements.html or simply www.amowc.com