Vitamin B12 Deficiency

What is Vitamin B12 deficiency?

Vitamin B12 is also known as cyanocobalamin and plays a vital role in cellular metabolism, particularly DNA synthesis and energy production. Vitamin B12 is absorbed in the small intestine after combining with a factor called the intrinsic factor that is released from the stomach. The deficiency of vitamin B12 causes the body to produce abnormal red blood cells leading to megaloblastic anaemia. Apart from this, it hampers transmission of nerve impulses and affects many other tissues like the hair follicle, spinal cord, etc.

What are the main associated signs and symptoms?

The early symptoms are mentioned below:

• Tiredness
• Lack of energy
• Breathlessness
• Fainting
• Headache
• Pale skin
• Sore tongue
• Ulcers in the mouth
• Irritability
• Weight loss
• Loss of appetite
• Tingling and numbness of limbs
• Early greying of hair

The severe symptoms are as follows:

• Decline in mental abilities
• Plaque formation in the blood vessels
• Obesity
• Hypertension
• High cholesterol
• Osteoporosis
• Loss of vision

What are the main causes?

Some of the causes of the deficiency are mentioned below:

• An autoimmune condition called pernicious anaemia that results in malabsorption of B12 in the intestine
• A family history of pernicious anaemia
• Lack of vitamin B12-rich foods in diet, such as fish, eggs, meat, and mushrooms
• Insulin and acidity medications that prevent adequate production of intrinsic factor in the stomach
• Surgical removal of the stomach or intestines
• Severe diseases of intestines like inflammatory bowel diseases
• Cancer
• Pregnancy

How is it diagnosed and treated?

A general examination of the patient, which involves a physical assessment of symptoms along with a detailed history helps diagnose the condition.

Blood tests include

• Haemoglobin levels – Less haemoglobin levels indicate anaemia
• Vitamin B12 levels
• Picture of red blood cells – Larger size of blood cells indicate a deficiency
• Measurement of indicators of B12, i.e., serum homocysteine or methylmalonic acid
• Schilling test to detect pernicious anaemia

The treatment modalities include

• Supplementation of oral or injection vitamin B12
• Dietary changes to include more foods that are rich in vitamin B12.

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3. Oh R,Brown DL. Vitamin B12 deficiency. Am Fam Physician. 2003 Mar 1;67(5):979-86. PMID: 12643357
4. Langan RC,Zawistoski KJ. Update on vitamin B12 deficiency. Am Fam Physician. 2011 Jun 15;83(12):1425-30. PMID: 21671542
5. Wolfgang Herrmann et al. Causes and Early Diagnosis of Vitamin B12 Deficiency. Dtsch Arztebl Int. 2008 Oct; 105(40): 680–685. PMID: 19623286
6. National Institutes of Health; Office of Dietary Supplements. [Internet]. U.S. Department of Health & Human Services; Vitamin B12.

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