Vitamin B12 is mainly used in the body for red blood cell development and also maintenance of the nervous system. It is absorbed after binding to intrinsic factor (secreted from parietal cells in the stomach) and is actively absorbed in the terminal ileum. A small amount of vitamin B12 is passively absorbed without being bound to intrinsic factor.

Vitamin B12 is found in meat, fish, eggs, milk but not in plants

Causes:

• pernicious anaemia: most common cause
• post gastrectomy
• vegan diet or a poor diet (vit B12 is only found in animal products)
• disorders/surgery of terminal ileum (site of absorption)
  • Crohn's: either diease activity or following ileocaecal resection
• metformin (rare)

PC

• sore tongue and mouth
• neurological symptoms
  • the dorsal column is usually affected first (joint position, vibration) prior to distal paraesthesia
• neuropsychiatric symptoms: e.g. mood disturbances

Investigations

• macrocytic anaemia

Management