I ve recently had a blood test to check Active B12 (holotranscobalamin) levels and it s come back as high. The standard range is 25.1 to 165 and my result is 256 (as the test doesn t measure above 256). This was a surprise as I m vegetarian so if anything I expected I may be low. I can t find much about high Active B12 levels online, other than suggesting they can be a symptom of serious problems such as blood cancers and liver/kidney problems. My other blood results (including liver and kidney function tests, red and white cell counts and platelets) have all come back fine. The only slightly high result was for Mean Cell Volume - a reading of 101, with a standard range up to 99. Should I be concerned with the high active B12 result? Thanks.