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Vitamin B12 Deficiency: Symptoms, Causes & Treatment

Updated in March 2022

Vitamin B12, also known as cyanocobalamin, is an vitamin that is essential for the synthesis of DNA, RNA and myelin. It is also required for the development of red blood cells. This vitamin is usually stored in higher quantities than other B-complex vitamins in the body. 

Some conditions can lead to a lack of this vitamin, causing symptoms like palpitations, fatigue and tingling in the hands and feet. 

The main causes of B12 deficiency include Crohn's disease, vegetarian diets or a low level of intrinsic factor, which is a substance the promotes the absorption of this vitamin. 

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Main symptoms 

A lack of vitamin b12 can lead to noticeable nervous system or cardiac symptoms. The most common symptoms include:

  1. Frequent fatigue or weakness
  2. Pernicious anemia
  3. Shortness of breath
  4. Palpitations
  5. Vision disturbances
  6. Loss of sensitivity or tingling in the hands and feet
  7. Lack of balance
  8. Confusion or memory loss 
  9. Possibility of dementia, which can be irreversible 
  10. Loss of appetite or weight loss with no apparent reason
  11. Frequently occurring mouth or tongue lesions 
  12. Irritability
  13. Recurrent feelings of sadness

In children, a lack of this vitamin can lead to growth impediments or delays, as well as megaloblastic anemia. 

What can cause a B12 deficiency 

A vitamin B12 deficiency can occur for many reasons, such as:

  • Changes in the stomach: Pernicious anemia can be caused by a decrease in intrinsic factor levels. This is a protein that is necessary for the absorption of B12 in the stomach. In addition, gastric acid is helps to separate B12 from the food that contains it. Gastritis or the use of certain medications can block or neutralize the acidity of stomach acid, which can interfere with the concentration of this vitamin in the stomach.
  • Changes in the intestine: People with Chrons disease who have a compromised ileum or have had their ileum surgically removed are unable to absorb B12 efficiently. Another common intestinal condition that can lead to B12 deficiency is the overgrowth of bacteria or parasites.   
  • Changes to diet: Animal-based foods are a natural source of B12. Therefore, people who have little-to-no intake of food like meat, fish, eggs, cheese and milk may experience a deficiency. People at highest risk for a deficiency are older adults, alcoholics, strict vegetarians or people with eating disorders. 

In addition, the use of medications, like antibiotics, metformin and medications that treat gastritis or ulcers (like omeprazole) may experience decreased B12 absorption in the intestine. Therefore, many people who use these medications may also be advised to supplement. 

How it is treated

Treatment for a B12 deficiency will vary depending on its cause. With pernicious anemia, for example, period IM injections of B12 and other B-complex vitamins may be necessary. 

When the cause is diet-related and there are no absorption abnormalities noted, the doctor may advise oral or injection supplementation of vitamin B12. He or she may also advise you to increase your intake of food that is rich in this vitamin. 

It is important for vegetarians to consume food that is rich in B12, like milk, tofu and grains, for example.

It is usually not possible to have excessive levels of this vitamin, as any excess B12 can be easily eliminated in the urine. However, people who have a history of polycythemia, cobalt allergy, cyanocobalamin allergy or are post-operative should not use B12 supplements without medical supervision.