This is hydroxocobalamin -- The best form -- The most bioactivity of all forms -- The most expensive, too! Your body uses this to make methyl- and adenosylcobalamin. This form is often used in injections. I feel GREAT when I take it! Methylcobalamin makes me a bit nervous and sleepless, and tends to give me a Headache. Biotics Research makes the highest quality supplements anywhere. See their resveratrol as an example of the extremely high quality of their products