Intrinsic factor

protein-coding gene in the species Homo sapiens

Intrinsic factor (IF), or gastric intrinsic factor (GIF), is a glycoprotein. It is produced by the parietal cells of the stomach.

IF is necessary for the absorption of vitamin B12 (cobalamin) later on in the ileum of the small intestine.[1] In humans, the gastric intrinsic factor protein is encoded by the GIF gene.[2]


  1. Pocock G, Richards C (2006). Human physiology: the basis of medicine (3rd ed.). Oxford University Press. p. 230. ISBN 978-019-856878-0.
  2. Alpers DH, Russell-Jones G 2013. Gastric intrinsic factor: the gastric and small intestinal stages of cobalamin absorption. a personal journey. (review). Biochimie. 95 (5): 989–94. [1]