Vitamin B12 deficiency

Vitamin B12 deficiency

Description, Causes and Risk Factors:

ICD-10: E53.8.

Vitamin B12 (cobalamin) plays an important role in DNA synthesis and neurologic function. Vitamin B12 deficiency can lead to a wide spectrum of hematologic and neuropsychiatric disorders.

Deficiency of vitamin B12 affects every cell in the body, but is most severely felt in the tissues where the cells normally divide rapidly, as in the blood forming tissues of the bone marrow and in the gastrointestinal tract. The nervous system is also affected and this may lead to degeneration of nerve fibres in the spinal cord and peripheral nerves.

The true prevalence of vitamin B12 deficiency in the general population is unknown. The incidence, however, appears to increase with age.

In humans, only two enzymatic reactions are known to be dependent on vitamin B12.

    In the first reaction, methylmalonic acid is converted to succinyl-CoA (Succinyl-Coenzyme A) using vitamin B12 as a cofactor. Vitamin B12 deficiency, therefore, can lead to increased levels of serum methylmalonic acid.

  • In the second reaction, homocysteine is converted to methionine (A crystalline amino acid containing sulfur; found in most proteins and essential for nutrition) by using vitamin B12 and folic acid as cofactors. In this reaction, a deficiency of vitamin B12 or folic acid may lead to increased homocysteine levels.

Vitamin B12 deficiency is most often caused by an inability of the body to properly digest and absorb vitamin B12. The inability to absorb vitamin B12 can be caused by diseases and conditions including:

    Pernicious anemia (a result of atrophic gastritis with poor B12 absorption).

  • Celiac disease (sensitivity to gluten from wheat and other grains, causing intestinal damage).

  • Atrophic gastritis (a condition in which the stomach lining is inflamed and becomes thin).

  • Crohn's disease (an inflammatory bowel disease that can affect any part of the intestine).

  • Surgical removal of a portion of the stomach or small intestine, such as with bariatric surgery.

  • In addition, some medications that treat diabetes, acid reflux, and peptic ulcers, for example, can affect how well your body can absorb vitamin B12.

  • Less commonly, vitamin B12 deficiency can occur as a result of not eating enough foods that contain vitamin B12. Foods that contain vitamin B12 include lean red meats, poultry, fish, brewer's yeast, and dairy products, such as milk, cheese, and yogurt.


Symptoms may include the following:

    Appetite loss.

  • Coordination disturbance (possibly ataxic gait if not treated).

  • Depression, disorientation, irritability, memory loss or impairment, and/or personality changes.

  • Facial pain, normally coming on one side at a time.

  • Fatigue and malaise.

  • Impairment of the sense of smell.

  • Lichtheim's disease (Subacute combined degeneration of spinal cord).

  • Mania and psychosis.

  • Migraines, which may follow after experiencing a temporary blind spot in the field of vision, at the center.

  • Nerve shock felt on a side of the body.

  • Neurological symptoms (sensory disturbances, irreversible nerve cell death, etc.).

  • Pernicious anemia and megaloblastic anemia (with enlarged blood corpuscles).

  • Pain in the hands - stabbing and/or tingling.

  • Shortness of breath, presenting without chest pain.

  • Sore, raw spots at the mouth corners, which can come and go.

  • Tingling along the back of the thighs.

  • Tingling and numbness in the extremities.

  • Tongue itching and/or tingling.

  • Twitching eyes, either on the eyelid or below the eye, typically in one eye at a time.

  • White spots on the skin, which may become dry, flaky, and raw as time passes.


The diagnosis of vitamin B12 deficiency has traditionally been based on low serum vitamin B12levels, usually less than 200 pg/mL (150 pmol/L), along with clinical evidence of disease. However, studies indicate that older patients tend to present with neuropsychiatric disease in the absence of hematologic findings.Furthermore, measurements of metabolites such as methylmalonic acid and homocysteine have been shown to be more sensitive in the diagnosis of vitamin B12deficiency than measurement of serum B12levels alone.In addition, folic acid deficiency can cause falsely low serum vitamin B12levels. One studyrevealed that approximately one third of patients with folic acid deficiency had low serum vitamin B12levels.

In addition, the doctor may order a Schilling test, a procedure during which the individual is given Vitamin B12 injections and tablets before tests are run to determine whether the vitamin is being absorbed properly. If the Vitamin B12 levels in blood are borderline, tests for blood levels for metabolites (e.g., homocysteine and methylmalonic acid) could be performed in order to either confirm or rule-out the diagnosis of cobalamin deficiency. A bone-marrow test may be performed in some cases, to allow for examination of cells under the microscope in order to further confirm the diagnosis.


Vitamin B12 deficiency

After the diagnosis of vitamin B12 deficiency has been made and a treatment plan has been initiated, follow-up is important to determine the patient's response to therapy.

Most cases of vitamin B12 deficiency that are due to the body's inability to properly absorb the vitamin through the digestive tract can be prevented only by successful treatment of the underlying cause. However, you may be able to lower your risk of vitamin B12 deficiency by:

    Eating a diet that includes a sufficient amount of vitamin B12, which is found in lean red meats, poultry, fish, and dairy products, such as milk, cheese, and yogurt. Various food products such as breakfast cereals are also fortified with vitamin B12.

  • Taking vitamin B12 supplements as recommended if you are at high risk for developing vitamin B12 deficiency, such as if you follow a vegan diet or have celiac disease or Crohn's disease.

  • Keep in mind that some medicines that treat diabetes, acid reflux, and peptic ulcer disease can affect how well your body absorbs vitamin B12. Most important, talk with your health care provider about any supplements, prescription medications, and over-the-counter medications you take.

Pharmacological Treatment Options May Include:

Treatment of vitamin B12 deficiency involves replacing the body's depleted stores of vitamin B12. This generally includes:

    A series of vitamin B12 injections, which may need to be a life-long treatment in cases in which the body cannot absorb vitamin B12.

  • Oral vitamin B12 replacement therapy may also be prescribed. Vitamin B12 may also be given through a nasal spray, or in a sublingual form that is absorbed under the tongue.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.


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