Vitamin B12


Vitamin B12 (also called cobalamin) is a water-soluble vitamin that is absorbed in the intestine, in order to help in the formation of red blood cells in the bone marrow, for healing and regeneration of skin and tissue and to help the body with its immunity.

Required Daily amount:

Life Stage Recommended Amount
Birth to 6 months 0.4 mcg
Infants  7–12 months 0.5 mcg
Children 1–3 years 0.9 mcg
Children 4–8 years 1.2 mcg
Children 9–13 years 1.8 mcg
Teens 14–18 years 2.4 mcg
Adults 2.4 mcg
Pregnant teens and women 2.6 mcg
Breastfeeding teens and women 2.8 mcg


a. Natural:

  • Eggs
  • Curds
  • Milk
  • Paneer
  • Meat (Poultry)

Vegetarians may have limited sources of Vitamin B12, as well as those on vegan diets. It is important to maintain healthy levels, by taking vitamin supplements if required. There may be cereals and grains also fortified with vitamin B12.

b. Supplements:

Supplements of vitamin B12 are available as both tablets and intramuscular injections, taken alone or in combination as multivitamins or B complex.

Health Benefits of Vitamin 12

  • Vitamin B12, helps in the formation of red blood cells which help to maintain hemoglobin level in the body. This carries oxygen to all body cells and tissues and aids cellular activity and metabolism. A deficiency of B12, results in abnormal forms of red blood cells in the peripheral blood, called macrocytes. Anemia caused due to low vitamin B12 levels is called Megaloblastic anemia.
  • It is also used in the formation of myelin sheaths of the nerves, which helps in conduction of impulses to transmit sensations, in addition to acting as a protective coating over the nerves. Deficiency of vitamin b12 therefore causes neuro-psychiatric symptoms like muscle pain, tingling numbness, delirium etc.
  • Vitamin B helps with immune function of the body
  • It also aids the formation of DNA in body cells
  • Studies have shown that vitamin b12 decreases the level of homocysteine in the blood, which is beneficial to patients with heart disease or ischemic stroke.

Deficiency of Vitamin B12

a. Nutritional defect

The most common cause of vitamin B12 deficiency is decreased intake in the diet. This is most commonly found with people on a purely vegetarian or vegan diet.

b. Decreased absorption:

  • In order to be absorbed by the body, vitamin B12 molecules require the presence of Intrinsic Factor (IF), a protein made by the stomach. Some people have a rare disease, which prevents the production of Intrinsic Factor, due to which they are unable to absorb the required amount of vitamin B12 from food sources or supplements. This is known as Pernicious Anemia.
  • Others may have conditions affecting the intestine which also hampers the uptake of vitamin B12, like Crohn’s disease, celiac disease, parasitic invasion.

Individuals with Vitamin B12 deficiency exhibit:

  1. Signs of Megaloblastic anemia, like weakness, lightheadedness, shortness of breath, pale skin and eyes. Blood tests may reveal a decrease in white and red blood cell count as well as platelet count, due to suppression in production in the bone marrow (pancytopenia)
  2. Neuropsychiatric manifestationswhich include myelopathy, neuropathy, dementia, and rarely optic ( nerve to the eye)  nerve atrophy SACD- Subacute Combined Degeneration of the Spinal Cord, typically includes a spastic paraparesis, extensor plantar response, and impaired perception of position and vibration, and may have associated peripheral neuropathy causing  stocking type numbness ( tingling numbness in the extremities), stiff limbs  and absence of ankle jerks. This is because the nerve fibres that control movement and sensation are damaged.
  3. Infants and children exhibit failure to thrive, movement difficulties and delayed milestones, and may show signs of jaundice.
  4. Rapid heart rate or tachycardia
  5. Memory loss, change in moods, depression, delirium, loss of memory –
  6. Gastro-intestinal issues like constipation or diarrhea
  7. Angular Stomatitis and cheilosis (inflammation at corners of the mouth)
  8. Macroglossia (inflamed, enlarged tongue pressing against the teeth)
  9. Bleeding gums

Excessive Intake of Cobalamin:

There are no known side effects of vitamin B12

Interactions with other medications

Certain medications can reduce the absorption of Vitamin B12 from the intestine like

  1. Antibiotics like chloramphenicol
  2. Antacids like Ranitidine, used to treat peptic ulcers
  3. Metformin used in the treatment of diabetes.


  1. Serum or blood levels of vitamin B12 can be measured to indicate deficiency. Correspondingly, serum homocysteine and serum lactate dehydrogenase levels are also known to be high in B12 deficiency. Peripheral blood examination (i.e. looking at the blood on a slide under a microscope) shows characteristic large, red blood cells called macrocytes, suggestive of Megaloblastic Anemia.
  2. T2 weighted Magnetic resonance imaging (MRI), show lesions classically involving the posterior and lateral columns of the spinal cord, indicating SACD.


Vitamin B 12 supplements can be given orally to those patients do have a nutritional deficiency, i.e. those who do not consume enough of the vitamin through food sources. For severe deficiency, or for those who have difficulty in absorbing the vitamin from the intestinal lining (malabsorption, Crohn’s disease, etc.) may need to take intramuscular injection supplements of the vitamin. This is not stored in the body for very long, so patients need to be monitored for levels to avoid deficiency in the future.

Disclaimer: The above information is for awareness and education purposes only and cannot be used for diagnosis or treatment of any condition. Please consult with a physician for any concerns or questions