← The FormularyLong gameVitamin B12
Also known as Methylcobalamin / cobalaminEasy to get. Easy to miss.
B12 is genuinely worth supplementing for the people who need it, and genuinely pointless for the people who do not — and the marketing does not distinguish. If you eat meat, have a normal gut and are not on metformin or long-term omeprazole, your B12 is almost certainly fine and an energy strip is not going to change how you feel. If you are vegan, over sixty, post gastric surgery, or on those drugs, it matters a great deal and a blood test is cheap. Our products carry it because it belongs in a complex, not because tiredness is a B12 problem.
A water-soluble vitamin made by bacteria, not by plants or animals, which is why it reaches you almost entirely through meat, fish, eggs and dairy — or fortification.
Absorption is the interesting part: B12 has to be released from food by stomach acid, bound to a protein called intrinsic factor, and collected at the very end of the small intestine. Break any link — low acid, gut surgery, certain drugs — and the vitamin is in the food and not in you. That is why supplemental doses look absurdly large against a 2.4 mcg requirement: only a small percentage of a large dose gets through passively.
Required to build red blood cells, to maintain the myelin sheath around nerves, and to run the methylation reactions the body uses constantly.
Vegans and vegetarians, anyone over sixty, anyone on metformin or long-term acid-reducing medication, anyone post gut surgery. Everyone else: probably already sufficient.
Daily, any time. Methylcobalamin is the pre-activated form; cyanocobalamin is cheaper, more stable and works for almost everyone.
If you were deficient, correction over weeks to months, and the nerve symptoms take longest. If you were not, nothing.
Grade A as an essential nutrient. No tolerable upper limit has been set because no consistent adverse effect has been found at high intake. Supplementation does not improve energy, mood or cognition in people who are not deficient, which is the claim most often made for it.
Read the labelNo established upper limit — excess is excreted. Do not use B12 to self-treat fatigue: persistent tiredness deserves a blood test. Metformin and long-term acid-reducing medication lower absorption; tell your doctor you take it.
Evidence grades describe how well an ingredient is studied — A well-supported, C emerging — not a promise of results. Educational, not medical advice. Doses are typical ranges; follow the label on the product.