Vitamin B₁₂ (Cobalamin) and Folate Deficiency

Abstract

Although deficiencies of vitamin B₁₂ (aka, cobalamin) and folate can present similarly with megaloblastic anemia, vitamin B₁₂ alone causes neuropsychiatric disorders. Therefore, replacement of the correct vitamin is essential to ensure a prompt cure. In developing countries, deficiencies of both vitamins commonly arise from dietary insufficiency. But in developed countries, malabsorption of vitamin B₁₂ is more common, especially because of food fortification with folate. The cause of deficiency of folate is often found in the past 6 months, whereas vitamin B₁₂ deficiency due to autoimmune pernicious anemia or food-B₁₂ malabsorption presents insidiously. Upon clinical suspicion of deficiency, conventional tests for serum folate and vitamin B₁₂ are appropriate, and specialized metabolite tests are needed when conventional test results are equivocal. However, in the setting of hemolysis or vitamin B₁₂ deficiency, the serum folate can be normal despite tissue folate deficiency. There are several established indications for prophylaxis with vitamin supplementation in the appropriate clinical setting.