Methylcobalamin (MeCbl): This is the most active form in the human body.
Cyanocobalamin (CNCbl): This synthetic version of vitamin B12 is created in a lab, which makes it the cheapest supplement option.
Hydroxocobalamin (HOCbl): Bacteria naturally creates this form of vitamin B12, making it the main type found in most foods.
Adenosylcobalamin (AdoCbl) : The energy formation that occurs during the Citric Acid cycle requires this form of B12.
The energy formation that occurs during the Citric Acid cycle requires this form of B12. Although naturally occurring, it is the least stable of the four types of B12 outside the human body and does not translate well into a tablet-based supplement. It can be difficult to find this one in supplement form, although some supplements, like Vegansafe™, have been able to stabilize it.