Vitamin B12

Methylcobalamin or cyanocobalamin?

Cyanocobalamin is a common supplement form; methylcobalamin, adenosylcobalamin and hydroxocobalamin are also available. The body can convert cyanocobalamin and hydroxocobalamin into active forms. NIH reports no evidence that absorption differs by supplement form, so the word “methyl” alone does not establish an advantage. 1

Why are tablet doses so much higher than the food reference?

The proportion absorbed falls sharply as the dose rises: NIH estimates about 2% absorption from a 500 µg dose and 1.3% from 1,000 µg. This helps explain why a treatment tablet can contain far more than a daily intake reference; it does not mean everyone needs a treatment-sized dose. 1

B12 in supplements and fortified foods is already free rather than bound to food protein. It therefore bypasses the initial release step in digestion. Oral and sublingual products have not shown different efficacy in the evidence summarized by NIH. 1

The cause of deficiency guides the choice

Injections are used for conditions such as pernicious anemia, malabsorption and severe deficiency. High-dose oral treatment can also raise blood levels, but the small comparative trials leave important symptom outcomes unanswered. A product comparison cannot replace a diagnosis of why B12 is low. 1 2