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Vitamin B12 Deficiency Anemia

This form of anemia occurs as a result of a lack of vitamin B12 (cobalamin). Vitamin B12 is essential for the formation of red blood cells, in particular. This anemia develops very slowly, after months or years of vitamin deficiency. The elderly are the most affected: about 12% of them would be deficient in this vitamin, without necessarily having anemia.

Vitamin B12 is obtained by eating foods of animal origin, such as meat, eggs, fish and shellfish. For most people, food brings much more B12 to the body than it needs. The excess is stored in the liver. It is possible to suffer from anemia because of a lack of B12 in the diet, but it is infrequent. Most often, anemia results from a problem of absorption of the vitamin.

The pernicious anemia affects 2% to 4% of the general population 2 . It is most likely under-diagnosed because the symptoms are not always obvious to detect.

Causes of Vitamin B12 Deficiency Anemia

An inability to properly absorb vitamin B12 in food: this cause is the most common. Here are the main elements that can lead to poor absorption.

A lack of intrinsic factor . The intrinsic factor is a secreted molecule in the stomach, which allows the absorption of vitamin B12 in the small intestine by binding to it (see diagram). For the link between intrinsic factor and B12 to occur, there must be a normal degree of acidity in the stomach. When anemia is caused by a lack of intrinsic factor, it is called pernicious anemia or Biermer anemia. Genetic factors would intervene.

Low acidity in the stomach  60% to 70% of vitamin B12 deficiencies in the  elderly  are due to a lack of gastric acidity 1 . With age, the cells of the stomach secrete less stomach acid and also less intrinsic factor. Regular and prolonged use of   antacid 3 drugs , such as histamine blockers (eg ranitidine) but in particular the class of proton pumps inhibitors (eg, omeprazole), also increases the risk 1 .

Metformin intake. People taking metformin, mostly to treat diabetes, are at higher risk of vitamin B12 deficiency 4 .

An autoimmune disease ( Graves’ disease , thyroiditis , vitiligo, etc.): in these cases, autoantibodies will bind the intrinsic factor, making it unavailable to bind vitamin B12.

Chronic bowel disease , which prevents the passage of vitamin B12 through the intestinal wall (eg, Crohn’s disease, ulcerative colitis or celiac disease). Vitamin supplementation is usually offered by the doctor to prevent deficiencies. In the case of celiac disease, absorption of vitamin B12 returns to normal once the  gluten-free diet  is adopted. Any other disease that causes malabsorption, such as chronic pancreatitis or very rarely parasite infestation, can cause vitamin B12 deficiency.

Some surgeries in the stomach or small intestine . Patients receive vitamin B12 supplementation as a preventive measure.

Anemia may also be due to a  lack of vitamin B12  in  the diet . But this situation is rather rare, as only small amounts of B12 are needed to meet the body’s needs. In addition, it has the capacity to make significant reserves, which can be sufficient for 3 or 4 years. Proponents of strict vegetarianism (also called  veganism ), who do not consume protein of animal origin, may suffer from anemia in the long run if they do not otherwise meet their B12 needs (see Prevention). Research has shown that 92% of vegans have a vitamin B12 deficiency if they do not take a supplement, compared to 11% of omnivores.


The vitamin B12 deficiency anemia moved very slowly, insidiously. This anemia can be treated easily and quickly. From the first days of treatment, the symptoms subside. In a few weeks, the deficiency can usually be corrected.

However, it is important to treat this type of anemia, because with the years,  neurological symptoms  can appear (numbness and tingling in the extremities, gait disorder, mood changes, depression, psychosis, dementia symptoms, etc.). These symptoms are longer to disappear (sometimes 6 months or more). Sometimes there are still some sequels.

People with pernicious anemia are slightly more at risk for stomach tumors than the rest of the population.

Diagnostic of Vitamin B12 Deficiency Anemia

The anemia caused by B12 deficiency is detected by various blood tests. The following anomalies are signs of it:

  • A decrease in the number of red blood cells, white blood cells and platelets;
  • A decrease in the hematocrit, that is, the volume occupied by the red blood cells relative to that of the blood;
  • A rate of hemoglobin lowered;
  • An increased size of red blood cells (mean cell volume or MCV): it may, however, remain stable if iron deficiency anemia (iron deficiency) is also present;
  • A change in the appearance of red blood cells and white blood cells, visible through the analysis of a blood smear.

There may be vitamin B12 deficiency without anemia.

The doctor also checks the levels of vitamin B12, folic acid and iron in the blood. We must also discover the cause of anemia. If a vitamin B12 deficiency is detected, a search for autoantibodies against the intrinsic factor is often undertaken.

Symptoms of Vitamin B12 Deficiency Anemia

There are not always obvious symptoms. These appear gradually.

The typical symptoms of anemia are: tiredness, pale, sometimes yellow skin tone, dizziness, increased heart rate, and increased shortness of breath on exertion.

A weak appetite.

Sometimes nausea and disturbed digestion (diarrhea or constipation).

The tongue red and dry.

Neurological symptoms, in case of greater deficiency: numbness and tingling in the extremities, poor coordination, mood disorders, memory loss, dementia.

People at risk

  • Men and women  65 years old and over.
  • People from Northern Europe (Caucasians) and African Americans.
  • Vegetarians and vegans
  • Patients with autoimmune diseases (Graves, vitiligo)
  • People who use metformin and some anti acids
  • People with certain types of surgeries in the stomach or intestines
  • People with malabsorption of any cause (crohn, celiac, chronic pancreatitis …)

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