Vitamin B12: Function, Deficiency and sources of Vitamin B12

Vitamin B12 (cobalamin) belongs to group of B vitamins which is a most structurally complicated vitamin. As it is a water-soluble vitamin, i.e. it absorbs in water and passes through blood stream; excess of it is immediately excreted from body. Therefore, our body needs B12 in sufficient amount.

Vitamin B12 function in the body

It plays crucial role in our body to work properly. It is important vitamin to keep nervous system healthy as well as for metabolism of each and every cell of human body by taking part in the synthesis of fatty acids and amino acids.

Also, this complex vitamin supports in production of DNA and red blood cells. It helps to prevent major diseases and birth defects. Additionally, it maintains normal brain function and keeps your mood up.

Not only this, but B12 is also an energy enhancer as it is important in energy metabolism. As Vitamin B12’s role is in cell production, it promotes healthy hair, skin and nails.

However, human body does not make on its own, so you need to get it from diet or supplements. Vitamin B12 is naturally found in animal products including meat, fish and dairy products.

Recommended daily intake of this vitamin is about 2.4 mcg. Human body stores B12 in liver for 3-5 years, so if you consume more it will be saved for future use.

Vitamin B12 deficiency

Vitamin B-12 deficiency occurs when you don’t consume enough of it from daily food or supplements. It is a medical condition in which blood levels of B12 are too low. The changes in level of vitamin B12 depend on how much B12 is obtained from diet, how much is secreted and how much is absorbed.

Vitamin B12 deficiency is more common in elders. The deficiency can lead to severe and irreversible damage, especially to nervous system and brain. Lower amount of B12 reduce healthy red blood cells (anemia).

Mild deficiency of this vitamin make you feel tired and promote lower number of red blood cells. Moderate case of this triggers neurological problems such as abnormal sensations like pins and needles or inflammation. Severe deficiency affects hearth health and causes greater neurological problems.

People are at risk of B12 deficiency when:

  • Elders
  • Following strict vegan diet
  • Inflammatory bowel disease
  • Gastritis
  • Chronic alcoholism
  • Having any medications that affects vitamin levels
  • Digestive disorder
Low levels of vitamin B12 can cause:
  • Poor brain functions
  • Permanent nerve damage
  • Temporary infertility in women
  • Memory loss
  • Increase the risk of stroke
  • Anemia
  • Peripheral neuropathy (nerve impairment)
  • Myelopathy (disease of the spinal cord)

Signs and symptoms of vitamin B12 deficiency

A mild deficiency may not have any perceptible symptoms, but more significant deficiency can have noticeable symptoms. Here are some signs and symptoms of vitamin B12 deficiency:

  • Weakness, fatigue, light-headedness
  • Depression, confusion or memory problems
  • Neurological changes such as tingling and numbness in hands and feet
  • Difficulty in maintaining balance
  • Pale or yellowing skin
  • Weight loss
  • Rapid heartbeat and short of breath
  • soreness of the mouth or tongue
  • constipation, diarrhea, loss of appetite
  • Dementia
  • Blurred or disturbed vision as a result of untreated B12 deficiency
  • Mood changes
  • bleeding gums
  • Anemia and pernicious anemia
  • In infants symptoms like poor growth, no desire for food and eventual growth problems if the deficiency left untreated.

All these symptoms sometimes mistaken as vitamin B12 deficiency as diagnosis of the deficiency is very complex. You need to consult a doctor for the proper understanding of the deficiency.


Diagnosis take place through blood tests or urine test. These tests check vitamin b12 deficiency by considering several factors:

  • Red blood cells count
  • level of folate and b12 are measured
  • methylmalonic acid (MMA)
  • homocysteine

Both MMA and Serum homocysteine are more accurate in diagnosing B12 deficiency due to their high b12 levels. Doctor suggests tests to get sure about deficiency based on symptoms you have. So consult a doctor if any of above symptoms you are experiencing.

Sources of vitamin B12

B12 is present in animal foods naturally, so if a person is omnivorous then that fellow can get enough of the vitamin. As it’s not generally available in plant foods, vegan or vegetarian people can get it from B12 fortified foods or supplements. Some great sources of B12 includes:

  • eggs
  • fortified cereals
  • Animal liver and kidneys (especially lamb liver)
  • Pork, Beef, chicken and poultry
  • Fortified Nutritional Yeast
  • Meat
  • fortified soymilk
  • Fish (Tuna, haddock)
  • Dairy products (milk, cheese, yogurt and other milk products)
  • Vitamin b12 supplements

Include b12-rich foods or supplements in your diet as a first step to treat b12 deficiency.

Vitamin b12 deficiency treatment

The very first step you can start to beat b12 deficiency is to make a habit to get proper diet with adequate amount of b12 for body. Deficiency symptoms can be easily avoidable by healthy diet.

If you are a vegan and not eating animal products, include fortified grains or soy-products in daily food intake to cover recommended intake of b12.

Vitamin b12 deficiency treatment depends on how much low level of b12 you have. If you have trouble in absorbing b12 or pernicious anemia, then you need high dosage of supplements or shots of vitamin.

There are many vitamin b12 injection or oral supplements available for treating deficiency. An adult should take daily supplement of vitamin b12 if deficient.

If the deficiency is a result of any underlying health condition then consult your doctor before proceeding to any of these treatments.

How much vitamin B12 do you need?

How much vitamin b12 you need is normally depends on your age and the state if pregnant or breastfeeding. Below is the list of average daily recommended intake for different ages:

Age Recommended Daily Intake (mcg)
birth to 6 months old 0.4 mcg
Infants (7 – 12 months) 0.5 mcg
Child (1 – 3 years) 0.9 mcg
Child (4 – 8 years) 1.2 mcg
Child (9 – 13 years) 1.8 mcg
Teenagers (14 – 18 years) 2.4 mcg
Adults (19 and older years) 2.4 mcg
pregnant women 2.6 mcg
Breastfeeding women 2.8 mcg

Start and maintain healthy balanced diet to serve your body sufficient amount of necessary vitamins and nutrients. By doing so you can prevent vitamin b12 deficiency. You can also choose to take supplements but make sure you let your doctor know about it so that he or she can make you aware about the dosage and side effects of it if any.