Vitamin B12 Deficiency

General text about anemia can be found here and text about vitamin deficiencies is written here.


Vitamin B12 or cobalamin is a compound that is not produced by our organism and we must to take in the diet. This substance co-works with folate (folic acid) and they are both necessary for proper creation of new cells including erythrocyte production in the bone marrow. Folic acid deficiency has a similar effect as vitamin B12 deficiency, but the symptoms are not usually less severe.


The lack of cobalamin may be caused by insufficient dietary intake. Typically, it is a case of chronic alcoholics and malnourished homeless people. More threatened are the alcoholics who drink hard liquors as vitamin B12 is present at least in beer. Larger amount of vitamin B12 is present in animal products including eggs, liver and other visceral organs. Vegetarians are another high-risk group of people, especially strict vegans who do not accept any animal products, so they are deficient in vitamin B12 very real risk.


Another possibility is malabsorption of cobalamin in the digestive tract. This can occur in various intestinal disorders causing the malabsorption syndrome.


An important reason of B12 malabsorption may be chronic atrophic gastritis, which is chronic inflammation of stomach mucosa caused by autoimmune process. From an unknown reason, our immune system starts to produce autoantibodies that begin to attack stomach mucosa. The mucous membrane of the stomach produces a special compound called the intrinsic factor, which is necessary for proper absorption of cobalamin in the intestine. Chronic inflammation of the gastric mucosa disrupts production of the intrinsic factor causing B12 malabsorption and so-called pernicious anemia. Chronic autoimmune gastritis is a risk factor for development of gastric cancer. Let us just add that surgical removal of a substantial portion of the stomach or of the small intestine may also impair absorption of B12 vitamin.


Anemia is the most typical manifestation of vitamin B12 deficiency. The patient suffers from anemic syndrome including weakness, fatigue, pallor, dizziness and exertional shortness of breath. The symptoms are related to insufficient oxygenation of muscles and brain. The lack of vitamin B12 (and folate) also manifests with deteriorated mental performance, tingling sensations of the extremities, diarrhea, oral thrush and non-infectious inflammation of the tongue (redness, burning sensations). The troubles are caused by impaired regeneration of mucous membranes in the digestive tract and nerve fibers.


The blood tests show decreased level of hemoglobin and enlarged volume of erythrocytes (larger erythrocytes). Serum level of vitamin B12 may be stated in a laboratory from a sample of venous blood. When the deficiency is confirmed, it is advisable to perform an upper GI endoscopy to examine the stomach mucosa and to acquire a small biopsy sample of the mucosa for histological examination to confirm or rule out the chronic stomach inflammation.


The best prevention is adequate dietary intake of B12 vitamin. When the problem is caused by malabsorption, it is necessary to supplement vitamin B12 in injection form. Patients with diagnosed chronic autoimmune gastritis should undergo regular upper GI endoscopy with taking samples of gastric mucosa to rule out precancerous mucosal changes.


The treatment consists mainly of regular administration of high doses of vitamin B12 in form of regular intramuscular or intravenous injections. The patient's blood count is repeatedly monitored to evaluate the effect of therapy. When the underlying cause is the chronic gastritis, the patient should be regularly endoscopically checked (see Diagnosis and Prevention).


Jiri Stefanek, MD  Author of texts: Jiri Stefanek, MD
 Sources: basic text sources