Vitamin B12, or cyanocobalamin, is a water-soluble vitamin. It is essential for cell growth and multiplication of cells. Inadequate concentrations of vitamin B12 indirectly decrease the concentration of folic acid, causing its functional deficiency. Low levels of B12 can cause anemia and damage to the central nervous system.
Normal and Abnormal Range
The normal level of vitamin B12 in serum is 150 to 660 pmol, or 200 to 900 pg/ml. Seventy percent of vitamin B12 in serum is protein-bound, and this constitutes the active form. The plasma concentration of vitamin B12 is the best routine measure of B12 deficiency, which should be suspected whenever the concentration falls below 150 pmol.
Sources of Vitamin B12
Vitamin B12 comes from ingestion of foods of animal origin, including fish and shellfish, red or white meat, liver, eggs and milk products. Vegetable products are free of vitamin B12. Strict vegetarians can have low vitamin B12 unless they consume multivitamin supplements or B12-fortified foods, like breakfast cereals, fortified soy products, fortified energy bars and fortified nutritional yeast.
Low B12 Conditions
Conditions that affect the stomach can cause B12 deficiency, because B12 requires intrinsic factor for absorption, which is produced by cells in stomach. Malabsorption conditions of the small bowel, pregnancy, dietary deficiency, HIV infection and certain drugs, like omeprazole, metformin and carbamazepine, can also cause low B12 levels.
Signs and Symptoms of Low B12
Low levels of vitamin B12 can cause production of abnormally large cells, called megaloblasts. Low levels can also cause the death of these cells during maturation, a phenomenon referred to as ineffective hematopoiesis. Severe deficiency affects all types of cells in the blood, resulting in decreased white and red blood cells and platelet deficiency. This can result in a depressed immune system, a megaloblastic type of anemia and clotting abnormality. Vitamin B12 deficiency can irreversibly damage the nervous system, causing abnormal pain and a "needle" sensation in the hands and feet, decreased vibration and position senses, with resultant unsteadiness, confusion, moodiness, loss of memory and decreased vision. The patient may exhibit delusions, hallucinations or even overt psychosis.
Treatment and Prevention of B12 deficiency
You can keep your vitamin B12 level normal by adequate diet intake. Strict vegetarians should take multivitamins and fortify their food intake. Vitamin B12 is available as an intramuscular injection or as an oral administration. It can also be combined with other vitamins and minerals as an oral supplement. Doses of 1 to 100 mcg are used for deficiency.
- "Goodman & Gilman's The Pharmacological Basis of Therapeutics," 11th edition; Laurence L. Brunton, John S. Lazo and Keith L. Parker; 2006
- "CURRENT Medical Diagnosis & Treatment 2011"; Stephen J. McPhee, Maxine A. Papadakis, Michael W. Rabow; 2011