Who should get tested for vitamin B12 (cobalamin) deficiency, and which is the best test to use: serum B12, methylmalonic acid (MMA), or holotranscobalamin levels?
This concludes our five-part video series on B12 this week. If you’re new to the issue, Vegan B12 Deficiency: Putting It into Perspective, and Safest Source of B12 are good places to start. The consequences of B12 deficiency can be grave (see Inverted Rabbit Sign). But getting enough is easy; B12 can be taken weekly (see Cheapest Source of Vitamin B12), or daily (see Daily Source of Vitamin B12). See my full recommendations.
2019 Update: My vitamin B12 recommendations have changed to reflect the latest science and labeling changes. If you’re relying on getting all your B12 from fortified foods, make sure you get at least one serving at each meal containing at least 190% of the Daily Value listed on the nutrition facts label (based on the new labeling mandated to start January 1, 2020–the target is 4.5 mcg three times a day). Probably easier to just follow my supplement recommendations instead, which have also changed: at least 50 micrograms of cyanocobalamin once a day or 2000 micrograms of cyanocobalamin once a week.
I put out some new B12 videos in 2020. Please see all of my newest videos on the topic page.