Vitamin B12: Deficiency Symptoms, Sources, and Treatments

Vitamin B12 is a vital nutrient for our body and most talked about vitamin. They play a very crucial role in keeping our nervous system, blood cells healthy, and synthesis DNA. It also helps in the prevention of megaloblastic anemia (a type of anemia) which causes weakness in body.

Since our body does not make vitamin B12 we need it to from food ( primarily animal-based) or dietary supplement.

It is a water-soluble vitamin. Hydrochloric Acid in our stomach helps to extract B12 from food or supplement and it gets combined with protein before getting absorbed in body.


Your body stores excess vitamin B12 in the liver, so if you consume more than the RDI, your body will save it for future use.


It is found naturally in some food including meats, fish, poultry, eggs, and dairy. It is also available in the market in the form of capsules and tablets as a dietary supplement. 

Vitamin B12 is found in almost all multivitaminsDietary supplements that contain only vitamin B12 or  with nutrients such as folic acid and other B vitamins (complex) are also available.

Vitamin B12 Deficiency Symptoms

Deficiency of Vitamin B12 has numbers of adverse effect and need medical attention immediately if you find any of the mentioned symptoms.

Typical symptoms are megaloblastic anemia, fatigue, weakness, constipation, loss of appetite, and weight loss. Lack of vitamin b12 also causes a change in neurology due to which you may feel numbness and tingling.

Deficiency symptoms also include megaloblastic anemia, fatigue, weakness, constipation, loss of appetite, weight loss, depression, confusion, dementia, poor memory, and soreness of the mouth or tongue.

In infant deficiency may cause thrive problems, movement problems, overall development.

The neurological symptoms of deficiency can occur without anemia, so early diagnosis and intervention are important to avoid irreversible damage. 


Many of these symptoms are general and can result from a variety of medical conditions other than vitamin B12 deficiency. (1)

Vitamin B12 treatment


In most cases, vitamin B12 deficiency is treated with injections as it is more effective and immediately absorbed. Oral doses are also the most common and

are generally effective. The effectiveness of oral doses depends on the absorption capacity of the body.

It is available in various form of injection, pills, capsules, sublingual and nasal gel.


You can also get the recommended amount  by eating a variety of foods such as fish, meat, poultry, eggs, milk, and other dairy products.


The amount of vitamin B12 you need each day depends on your age. Average daily recommended amounts for different ages are listed below in micrograms (mcg):


Recommended Dietary Allowances (RDAs) for Vitamin B12 
0–6 months*0.4 mcg0.4 mcg  
7–12 months*0.5 mcg0.5 mcg  
1–3 years0.9 mcg0.9 mcg  
4–8 years1.2 mcg1.2 mcg  
9–13 years1.8 mcg1.8 mcg  
14+ years2.4 mcg2.4 mcg2.6 mcg2.8 mcg

* Adequate Intake

Vitamin B12 Food sources

  • Liver and Kidneys (animal organ Meat):
    These are rich sources of B12 and a good deal of nutritious food. It contains about 70.7 mcg B12 per 3 ounces of meat. It also contains vitamin A and B2 with copper and selenium.
  • Clams:
    Clams are very high on nutrients especially B12. It is also a good source of protein and it contains 84 mcg in 3 ounces. These small shellfish also provide iron and are good source of antioxidants.
  • Sardines:
    These are small fish power packs with most of the nutrients.It is a food source of omega-3 fatty acids.
  • Beef:
    Beef is an excellent source of vitamin B12. 3 ounces of beef provides 1.5 mcg of B12. It also contains B2, B3, and B6.
  • Fortified cereal:
    It is good vegetarian sources of B12 and is synthetically made without using any animal products. You can get 6 mcg in 1 cup. Cereal comes will the variety of added minerals and vitamins which are important for our body and are a good food option for both vegetarians and non-vegetarians.
  • Tuna:
    Tuna Fish are rich in vitamins minerals and protein. They are widely consumed worldwide. You get 2.5 mcg in 3 ounces of tuna.
  • Trout:
    Trout is freshwater fish and you can get 5.4 mcg of B12 in 3 ounces. These are also great source protein, healthy fats, and B vitamins.
  • Salmon:
    Salmon is well known for having one of the highest concentrations of omega-3 fatty acids. You can get 4.9 mcg of B12 in 3 ounces.
  • Milk and dairy products:
    Milk and dairy products like yogurt and cheese are great sources of protein and several vitamins and minerals, including vitamin B12. You can get 1.2 mcg of B12 in one cup of low-fat milk.
  • Eggs:
    Eggs are a great source of complete protein and B vitamins, especially B2 and B12, and provide 0.6 mcg in one large egg.


Vitamin B12 can interact or interfere with medicines that you take, and in some cases, medicines can lower vitamin B12 levels in the body. 


Tell your doctor, pharmacist, and other healthcare providers about any dietary supplements and medicines you take. They can tell you if those dietary supplements might interact or interfere with your prescription or over-the-counter medicines or if the medicines might interfere with how your body absorbs, uses, or breaks down nutrients. 


People should get most of their nutrients from food, advises the federal government’s Dietary Guidelines for Americans. Foods contain vitamins, minerals, dietary fiber, and other substances that benefit health. In some cases, fortified foods and dietary supplements may provide nutrients that otherwise may be consumed in less-than-recommended amounts.