B12 and vegetarian diet

According to Dietary Supplement Fact Sheet of Vitamin B12 (info provided  by a unit under National Institutes of Health of USA) in web page 

http://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/

Strict vegetarians and vegans are at greater risk than lacto-ovo vegetarians and non-vegetarians of developing vitamin B12 deficiency because natural food sources of vitamin B12 are limited to animal foods. Fortified breakfast cereals are one of the few sources of vitamin B12 from plants and can be used as a dietary source of vitamin B12 for strict vegetarians and vegans.

My note --- My opinion is : for vegans and vegetarians, a good source of B12 is B12 supplements obtained from your family doctor (GP) instead of buying from health supplements shops. Tell your doctor you are on vegetarian diet and get medical advice from him.