Video narration
How does vitamin B12 get from your meal into your bloodstream-does it just pass straight through the gut? Think of B12 as a package moving through a delivery system. In food, it arrives attached to proteins, so it is not ready for delivery. In the stomach, acid and digestive enzymes unpack it, freeing the B12 package. Here's the turn: B12 cannot simply cross into your blood. It needs a carrier. That carrier is intrinsic factor, a stomach-made protein. Intrinsic factor picks up B12 and carries it onward. The pair travels through the small intestine to the ileum, the final checkpoint near its end. There, B12 is admitted through the intestinal wall. From there, it enters the bloodstream. So the answer is: B12 must be unpacked, carried by intrinsic factor, checked at the ileum, and sent into your bloodstream.