Vitamin B12 Deficiency: What You Need to Know

Medically Reviewed By Lauren Castiello, MS, AGNP-C
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Vitamin B12 deficiency is a condition in which the body has inadequate stores of vitamin B12. Vitamin B12 is a nutrient that is essential to many processes in the body. A vitamin B12 deficiency can cause symptoms such as fatigue, mood changes, decline in mental ability, and mouth ulcers. Vitamin B12 is essential for many aspects of health, including the production of red blood cells. Healthy numbers of red blood cells are critical for delivering oxygen and nutrients to the body’s cells and tissues.

A low level of vitamin B12 may affect the function of the body.

This article will discuss the symptoms, causes, and treatments of vitamin B12 deficiency. It will also discuss complications and how you can improve your vitamin B12 level at home.

What is vitamin B12 deficiency?

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Vitamin B12 is a water-soluble vitamin gained from the food you eat. Vitamin B12 is necessary for the function and development of the central nervous system, healthy red blood cell production, and DNA synthesis.

To maintain optimal health, you need to consume vitamin B12 daily and effectively absorb it in the digestive tract.

Most people get enough vitamin B12 by including a variety of foods in their diet.

Foods that naturally contain vitamin B12 include lean red meats, poultry, fish, brewer’s yeast, and dairy products. Food producers may also add vitamin B12 to some breakfast cereals, breads, and other fortified food products.

Uncontrolled or untreated vitamin B12 deficiency can lead to complications, such as anemia, nerve damage, and growth irregularities.

What are the symptoms of vitamin B12 deficiency?

Symptoms vary depending on the individual, the underlying cause, the severity of the deficiency, and other factors. In some cases, symptoms can be vague, take years to develop, or may not be noticeable.

A low level of vitamin B12 can affect the gastrointestinal tract, the cardiovascular system, and the nervous system.

Symptoms may include:

Neurological symptoms may include:

  • lack of balance and affected reflexes
  • impaired memory, cognition, and judgment
  • psychological conditions, such as depression, dementia, confusion, personality changes, or developmental delay
  • paraesthesia, the feeling of pins and needles, and altered sensation
  • disturbed vision
  • loss of taste or smell
  • convulsions

What causes vitamin B12 deficiency?

Various conditions may cause a low level of vitamin B12, including:

  • pernicious anemia
  • atrophic gastritis
  • surgery or trauma to the gastrointestinal system
  • gastrointestinal disorders, such as celiac disease, Crohn’s disease, or fish tapeworm
  • autoimmune endocrinopathy from conditions such as diabetes or hypothyroidism
  • congenital conditions and hereditary genetic abnormalities, such as Imerslund-Gräsbeck syndrome

Some medications can affect how your body absorbs vitamin B12. These include anticonvulsant medications and medications that treat diabetes, acid reflux, and peptic ulcers.

A less common cause is diet, not eating enough foods that contain vitamin B12.

What are the risk factors for vitamin B12 deficiency?

Factors that may contribute to developing a vitamin B12 deficiency include:

  • being an older adult
  • having a health condition that affects absorption of nutrients
  • undergoing gastrointestinal surgery
  • eating a vegan diet

People who eat no dairy or eggs have a higher risk of developing vitamin B12 deficiency if they also do not eat meat. As a result, infants that consume breast milk from people who do not consume animal products may also develop vitamin B12 deficiency.

Additionally, a pregnant person with pernicious anemia may increase the risk of the infant being born with a vitamin B12 deficiency. In this case, the infant’s deficiency can be severe even if the gestational carrier’s deficiency is only mild.

How can you reduce your risk of vitamin B12 deficiency?

An underlying condition that prevents your body from properly absorbing vitamin B12 makes it difficult to maintain a healthy level of B12. In this case, you must successfully treat the underlying condition.

In addition, eating a diet that includes a sufficient amount of vitamin B12 can help. Vitamin B12 is present in lean red meats, poultry, fish, and dairy products. Some foods, such as breakfast cereals and other grains, are fortified with vitamin B12.

A 2016 study suggests the following meat-free or plant-based sources of vitamin B12:

  • egg and milk products, such as yogurt
  • soy beverages and products
  • breakfast cereals fortified with B12
  • nutritional yeast

Mushrooms, seaweed, and fermented foods such as tempeh, sauerkraut, and natto may offer vitamin B12. However, the amount of B12 in each can vary greatly.

Some medications that treat diabetes, acid reflux, and peptic ulcer disease can affect how well your body absorbs vitamin B12. However, continue taking all your medications as prescribed.

If you are concerned about the way your medication may be affecting your nutrition and health, contact your doctor. They will review any supplements, prescription medications, and over-the-counter medications you take. Your doctor can answer your questions and advise you on any changes.

If you are at high risk for developing a vitamin B12 deficiency, some clinicians recommend regular monitoring of B12 levels. Treatment for a low level of vitamin B12 should begin promptly.

How is vitamin B12 deficiency treated?

Vitamin B12 deficiency is treatable. Treatment involves replacing the body’s depleted stores of vitamin B12.

Your doctor will confirm a low level of vitamin B12 with a blood test. For people who are not getting enough vitamin B12 in the diet, oral supplements may be an effective treatment.

In cases where there is poor absorption of nutrients, larger doses or regular treatment may be necessary.

Treatment options generally include:

  • a series of vitamin B12 injections, a lifelong treatment if the body cannot absorb vitamin B12
  • oral vitamin B12 replacement therapy, including pills, drinkable liquids, and nasal and oral sprays
  • diet changes to include more lean red meats, poultry, fish, and dairy products
  • treatment of the underlying cause of the deficiency

Contact your doctor to develop a treatment plan that is best for you.

What are the potential complications of vitamin B12 deficiency?

If a low level of vitamin B12 is untreated, symptoms may worsen. Serious complications may develop, including:

  • anemia, with further severe complications such as heart failure
  • developmental delays in infants
  • congenital disorders
  • dementia
  • depression
  • disabling neurological conditions
  • increased risk of gastric cancer
  • increased risk of developing an autoimmune disorder, such as Hashimoto’s disease, rheumatoid arthritis, or type 1 diabetes

Other frequently asked questions

Here are some questions people often ask about vitamin B12 deficiency.

Why do B vitamin deficiencies lead to lack of energy?

Low levels of B vitamins impair the production of red blood cells and the supply of oxygen. An insufficient supply of oxygen may lead to feelings of fatigue and tiredness.

Is B12 deficiency serious?

Some cases of vitamin B12 deficiency are mild and easily treatable. Others, or untreated cases, can lead to serious complications. These can include bleeding, infection, brain or nerve function impairment, and congenital disorders or developmental delays in infants.

How can I raise my B12 levels fast?

You can raise your vitamin B12 level by including sources of B12 in your diet or taking supplements. Supplements can include over-the-counter tablets and liquids, as well as B12 injections.

Contact your doctor before starting any new supplement. As with all supplements and medications, B12 supplements can have side effects and risks. Your doctor will advise you on the most appropriate and safe option for you.

What is the main cause of vitamin B12 deficiency?

One of the most common causes of vitamin B12 deficiency is pernicious anemia. This is an autoimmune condition that damages the cells in the stomach. The body is then less able to absorb vitamin B12.

Read on here for more information about pernicious anemia, including its symptoms and treatment.

Which fruit is rich in vitamin B12?

Most fruits, vegetables, or other plant-based foods do not contain vitamin B12. Some may contain vitamin B12 in only trace amounts.

Vegan B12 supplements or supplements free from animal products can also help you meet daily nutritional requirements for vitamin B12. Contact your doctor for advice before starting supplements.


Vitamin B12 is a nutrient that is essential to the health of the body. Deficiency of vitamin B12 can lead to symptoms such as fatigue, neurological or psychological changes, mouth ulcers, and changes to sensation and vision.

Diet, some health conditions, gastric surgery, and certain medications may lead to vitamin B12 deficiency.

Treatment can include over-the-counter B12 supplements, B12 injections, as well as successful treatment of an underlying cause.

Complications of severe B12 deficiency can include infertility, developmental delays in children, and risk of further illness.

Contact your doctor regarding any symptoms of vitamin or nutrient deficiency.

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Medical Reviewer: Lauren Castiello, MS, AGNP-C
Last Review Date: 2022 Jun 16
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THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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