Causes

• pernicious anaemia
• tropical sprue
• bowel resection
• jejunal diverticula
• cobalamin malabsorption
• vegetarianism 

Note:

• 12%-17% of elderly people in the community have cobalamin deficiency, ^c but only 2% develop pernicious anaemia ^b

Pernicious anaemia , tropical sprue and bowel resection are the commonest causes of cobalamin deficiency

cause of cobalamin deficiency	% (95% CI)
pernicious anaemia c	76% (72% to 81%)
tropical sprue	9.6% (6.7% to 13%)
bowel resection	6.7% (4.2% to 9.1%)
jejunal diverticula	1.5% (0.3% to 2.7%)
food cobalamin malabsorption	0.7% (0.0% to 1.6%)
vegetarianism	0.5% (0.0% to 1.2%)
unknown	4.7% (2.6% to 6.7%)