I have recently had my routine blood word. He also did a B12 and D3 test. My B12 came back high at 1600. He rechecked it 10 days later and it was the same. I have Hashimoto's Thyroiditis and Mast Cell Activation Disorder. I know a high level can be caused by blood diseases and tumors but was wondering if it could be caused by my Hashimoto's or the MCAD or something less benign.