"Longterm vegans should supplement Vitamin B12 - yes, I agree. But it turns out taking B12 has possible risks, like some other supplements. Today we look at research showing the potential problems of raising your B12 blood levels too high, which could include death. If you’re a longterm vegan, DO take B12, but be careful not to go hog wild. I discuss why I’ve temporarily stopped taking B12, and am monitoring my levels. My decision to coast for a bit is based on recent research, discussed in this video.
If you adhere to a vegan diet, B12 supplementation is prudent. I also recommend having yourself tested for vitamin B12 deficiency every few years. The most appropriate test for evaluating B12 status is the urine test for methylmalonic acid (MMA). Elevated MMA is currently the best tool for detecting vitamin B12 deficiency, and is considered to be superior to testing for serum B12 directly. An alternative and less costly screening blood test is Homocysteine."