Vitamin B12 deficiency

Vitamin B12 deficiency, also known as cobalamin deficiency, is the medical condition in which the blood and tissues have a lower than normal level of vitamin B12.

Mild deficiencies may have few or absent symptoms. In moderate deficiencies, feeling tired, feeling faint, mouth ulcers, rapid breathing, upset stomach, pallor, hair loss, decreased ability to think and joint pain and the beginning of neurological symptoms, including abnormal sensations such as, numbness and tingling, and tinnitus may occur. Severe deficiencies may include symptoms of reduced heart function, suppression of bone marrow, as well as more various severe neurological symptoms possibly including sensory loss, abnormal balance and reflexes, memory and consciousness impairment, smell and taste problems, depression, irritability, confusion, and psychosis. If left untreated, some of these changes can become permanent. Onset of deficiency may take years to develop. In exclusively breastfed infants of vegan mothers, undetected and untreated deficiency can lead to poor growth, poor development, and difficulties with movement.

In healthy adults, vitamin B12 deficiency is not common, mainly because body stores of the vitamin are substantial and turnover is slow, with relatively low dietary requirements. Risk factors may occur possibly more in elderly people due to impaired intestinal absorption, and in children, premenopausal women, and pregnant women, whose diets are low in animal foods.

Causes are usually related to conditions that give rise to malabsorption of vitamin B12, particularly autoimmune gastritis in pernicious anemia.