Vitamin B12 deficiency: an overview and more


Vitamin B12 deficiency is a fairly common disease in children and adults. In addition to low dietary intake, other factors that can cause vitamin B12 deficiency include gastric bypass surgery and gastrointestinal (GI) malabsorption diseases .

Diagnosing a vitamin B12 deficiency can be challenging because there are many symptoms that resemble other conditions, such as fatigue, muscle weakness, and cognitive difficulties.

Treatment generally involves taking vitamin B12 supplements or injecting the vitamin. If you have a disease that predisposes you to vitamin B12 deficiency, it is important to address the medical cause as well.

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Symptoms of vitamin B12 deficiency

Due to the complex and overwhelming role that vitamin B12 plays in the body, there are many potential symptoms.

Many symptoms are associated with four main categories of vitamin B12-related complications:

Complication of vitamin B12 deficiency Symptoms
Anemia (violation of red blood cells) Fatigue, dizziness, paleness, and heart palpitations.
Neuropathy (nerve degeneration) Tingling, numbness, weakness, and balance problems.
Myelopathy (spinal cord injury) Sensory problems, numbness, tingling.
Dementia Cognitive impairment and behavioral changes.


Vitamin B12 plays a role in the production of red blood cells (erythrocytes), which normally carry oxygen throughout the body. Since oxygen is a vital part of your body's energy production, if there is a defect in red blood cells (which occurs when vitamin B12 is deficient), anemia develops .


Vitamin B12 is also a vital part of a healthy nervous system, and its absence causes slow degeneration of nerves in the brain, spinal cord, and peripheral nerves. The weakness and imbalances associated with neuropathy (impaired nerve function) can be exacerbated when anemia is also present .


Myelopathy, a spinal cord dysfunction, occurs when neurons in the posterior spinal cord are damaged. This leads to muscle weakness and the inability to recognize light touch, vibration, and proprioception (a sense of position). Some symptoms similar to neuropathy are also common.


Vitamin B12 deficiency can cause dementia , leading to memory and cognitive loss, behavior changes, and self-care problems. With a severe and chronic deficiency of vitamin B12, psychosis can develop.

Other symptoms

Other symptoms and signs of vitamin B12 deficiency can include :

  • Low white blood cell count, which increases the risk of infection.
  • Low platelet count, which increases the risk of bleeding.
  • Headache
  • Weightloss
  • Mood swings, especially depression
  • Behavior changes
  • Trouble walking
  • Loss or diminished sense of smell.
  • Swollen tongue (called glossitis)

Symptoms of vitamin B12 deficiency usually develop gradually over weeks to months and generally do not improve without treatment.


The two main causes of vitamin B12 deficiency are inadequate intake and malabsorption in the intestines.

Inappropriate consumption

Vitamin B12 is found in animal proteins such as fish, meat, and milk, and in some fortified grains. Regular vegetarians or vegans who do not take supplements can develop a B12 deficiency due to inadequate dietary intake of the vitamin. People who abuse alcohol and the elderly are also at risk for vitamin B12 deficiency .


Because vitamin B12 is absorbed from the intestines through a complex process that relies on a protein called intrinsic factor , intestinal malabsorption can also lead to vitamin B12 deficiency.

Causes of intestinal absorption of vitamin B12 include :

  • Pernicious anemia, an autoimmune disease in which antibodies attack cells that release intrinsic factor.
  • Inflammatory diseases of the gastrointestinal (GI) tract, such as Crohn 's disease and celiac disease .
  • Long-term use of certain medications, such as metformin and proton pump inhibitors (PPIs)
  • Gastric bypass surgery, which involves the resection of parts of the stomach and / or small intestine.
  • Gastrointestinal resection surgery, which is a treatment for serious medical problems such as intestinal obstruction or cancer.


While the diagnosis of vitamin B12 may seem straightforward, it is not always obvious. This is because many of the common symptoms of vitamin B12 deficiency overlap with the symptoms of other health conditions.

Your healthcare team may consider a variety of diagnoses in addition to vitamin B12 deficiency as they work to explain your symptoms.

History and physical exam

In addition to a medical history that can reveal symptoms such as unexplained fatigue, numbness, and tingling, a physical exam can reveal signs of vitamin B12 deficiency .

For example, a weak and fast pulse or pale fingers can be a sign of anemia. Decreased feeling in the legs and decreased reflexes can be a sign of neuropathy. Finally, confusion or communication difficulties are common signs of dementia and depression.

Lab tests

Laboratory tests, such as a complete blood count (CBC) and vitamin B12 levels, can confirm the diagnosis of vitamin B12 deficiency .

Also, often with a vitamin B12 deficiency, a specific type of anemia called macrocytic anemia (not to be confused with pernicious anemia) can be identified by a blood smear . Red blood cells appear large and can vary in shape and size.

Visualization and specialized tests

While certain imaging tests and nerve conduction studies (NCV) may be helpful in evaluating the effects of a vitamin B12 deficiency, they do not provide a specific pattern of results that matches this deficiency. Therefore, if you are satisfied, the results should be considered in conjunction with other evaluations.

Watch out

Vitamin B12 deficiency can be controlled with oral (oral) or intramuscular (IM) injections of the vitamin. If decreased absorption is one of the causes of vitamin B12 deficiency, you may need an injection to get it absorbed. directly on your body.

The cause of your B12 deficiency should be addressed whenever possible, especially if you have not undergone surgical resection or are unsure why you have low levels of this vitamin.

Depending on the cause of the vitamin deficiency, you may need to continue taking vitamin B12 supplements throughout your life, even after your symptoms improve .

Recovery from a vitamin B12 deficiency takes time, and you may not feel any improvement during the first few months of treatment. The improvement can be gradual and last six to 12 months.


You may continue to suffer from long-term vitamin B12 deficiencies, such as numbness, tingling, and weakness. These effects can upset your balance. Working with a physical or occupational therapist can help you optimize your ability despite these long-standing challenges.

Also, memory problems may improve as vitamin B12 levels are adjusted, but you may continue to experience some cognitive (thinking) deficits for a long time.

Rehabilitation and cognitive therapy are challenging, but they can help you maximize and improve your thinking and problem-solving skills.

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Vitamin B12 deficiency can be difficult to diagnose because the effects and symptoms are so varied. You may not experience the sudden effects of vitamin deficiency, but instead go through periods of gradual or intermittent decline in vitamin B12 levels, resulting in subtle or temporary symptoms.

If you have inflammatory gastrointestinal disease or have had a gastric resection, you may need preventive treatments such as regular injections of vitamin B12 to avoid vitamin B12 deficiency.

Frequently asked questions

  • Normal levels of vitamin B12 are 160 to 950 picograms per milliliter (pg / ml) or 118 to 701 picomoles per liter (pmol / L).

  • This is quite common. In the United States, about 6% of adults younger than 60 are B12 deficient, but nearly 20% of adults older than 60. Deficiency is more common in older adults, as the ability to metabolize vitamin B12 decreases with age.

  • Yes, there are several medications that can interact with B12 and cause malabsorption. These include acid-reducing drugs (histamine 2 receptor antagonists and proton pump inhibitors) and metformin.

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