What is the most likely reason for the development of a vitamin b12 deficiency ?

Vegans are especially at risk for B12 deficiency due to the lack of the vitamin in their diet. Vegetarians are also at risk but due to less strict dietary constraints their chances for B12 consumptions are drastically higher than a vegan's. B12 is found primarily in meat, eggs and dairy products.

2mcg of demopressin actate or half of the 4mcg/ml container.