Vitamin B12 deficiency can lead to some serious health problems. Prolonged B12 deficiency can lead to nerve degeneration and irreversible neurological damage. Anemia is another health disorder that can result due to B12 deficiency. B12 is vital for DNA synthesis. B12 deficiency can disrupt DNA production and abnormal cells called megaloblasts occur resulting in anemia.

Inadequate amount of Vitamin B12 can also weaken the immune system and the body’s natural resistance leading to excessive tiredness, breathlessness, listlessness, pallor, and poor resistance to infection.

Generally B12 deficiency is a result of the body’s inability to effectively absorb Vitamin B12 from the small intestine rather than a result of inadequate dietary consumption. Absorption of B12 requires the secretion from the cells lining the stomach of a glycoprotein, known as intrinsic factor. Certain people are unable to produce intrinsic factor putting them at a greater risk of developing a condition called as pernicious anemia. This type of anemia can be treated with injections of B12.

Non meat-eaters (including vegans and some vegetarians) generally get their required B12 from reabsorption than from dietary sources. Reabsorption is the reason it can take over 20 years for deficiency disease to develop in people changing to diets absent in B12. Contrary to this, if B12 deficiency is the result of failure in absorption it may take only 3 years for deficiency diseases to occur.