From Wikipedia, the free encyclopedia

Vitamin B12 deficiency
Other namesHypocobalaminemia, cobalamin deficiency
Cyanocobalamin.svg
Cyanocobalamin
SpecialtyNeurology, hematology
SymptomsDecreased ability to think, depression, irritability, abnormal sensations, changes in reflexes
ComplicationsMegaloblastic anemia
CausesPoor absorption, decreased intake, increased requirements
Diagnostic methodBlood levels below 120–180 picomol/L (170–250 pg/mL) in adults
PreventionSupplementation in those at high risk
TreatmentSupplementation by mouth or injection
Frequency6% (<60 20="" old="" years="">60 years old)

Vitamin B12 deficiency, also known as cobalamin deficiency, is the medical condition of low blood levels of vitamin B12. In mild deficiency a person may feel tired and have a reduced number of red blood cells (anemia). In moderate deficiency there may be inflammation of the tongue and the beginning of neurological problems including abnormal sensations such as pins and needles, while severe deficiency may include reduced heart function and greater neurological problems.

 Neurological problems may include changes in reflexes, poor muscle function, memory problems, decreased taste, and in extreme cases psychosis. Sometimes temporary infertility may also occur. In young children symptoms include poor growth, poor development, and difficulties with movement. Without early treatment, some of the changes may be permanent.

Common causes include poor absorption from the stomach or intestines, deficient intake, and increased requirements. Decreased absorption may be due to pernicious anemia, surgical removal of the stomach, chronic inflammation of the pancreas, intestinal parasites, certain medications, and some genetic disorders. Medications that may decrease absorption include proton pump inhibitors and metformin. Decreased intake may occur in vegetarians or people who are malnourished. Increased requirements occur in people with HIV/AIDS, and in those with rapid red blood cell breakdown. Diagnosis is typically based on blood levels of vitamin B12. Elevated methylmalonic acid levels may also indicate a deficiency. A type of anemia known as megaloblastic anemia is often but not always present.

Treatment consists of using vitamin B12 by mouth or by injection; initially in high daily doses, followed by less frequent lower doses as the condition improves. If a reversible cause is found, that cause should be addressed if possible. If no reversible cause is found - or when found it cannot be eliminated - lifelong vitamin B12 administration is usually recommended. Vitamin B12 deficiency is preventable with supplements containing the vitamin: this is recommended in pregnant vegetarians and vegans, and not harmful in others. Risk of toxicity due to vitamin B12 is low.

Vitamin B12 deficiency in the US and the UK is estimated to occur in about 6 percent of those under the age of 60, and 20 percent of those over the age of 60. In Latin America, rates are estimated at 40 percent and they may be as high as 80 per cent in parts of Africa and Asia.

Signs and symptoms