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Vitamin B12 Deficiency

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B12 deficiency can cause serious and irreversible damage to the nervous system and lead to difficulties in cognition, balance, motion, and an inability to create sufficient blood cells to supply the body with oxygen. Taking recommended B12 supplements is usually the best treatment.

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Take a quiz to find out if you have vitamin B12 deficiency.

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What is vitamin B12 deficiency?

B12 is an essential vitamin for the production of myelin, a compound that speeds up the conduction of nerve impulses, and the production of red blood cells, the cells that carry oxygen throughout the body. It only occurs naturally in diets containing animal byproducts.

B12 deficiency can cause serious and irreversible damage to the nervous system and lead to difficulties in cognition, balance, motion, and an inability to create sufficient blood cells to supply the body with oxygen.

The main and most effective treatment is taking B12 supplements with a specific recommendation from a medical provider.

You should visit your primary care physician to discuss your symptoms.

Vitamin B12 deficiency symptoms

B12 deficiency occurs more frequently in extreme poverty or in diets that intentionally restrict animal products (e.g. veganism, vegetarianism). Details regarding symptoms include the following.

Cognitive decline

Because B12 is important in the creation of myelin, as less of it is available within the body, the myelin that is created is thought to be of lower quality and then absent. This can lead to:

  • Changes in mood, depressed mood, and irritability
  • Insomnia
  • Cognitive slowing and forgetfulness
  • Dementia: This can occur in extreme cases.
  • Optic nerve breakdown: Psychosis and visual disturbances can occur due to the breakdown of the optic nerve also in extreme cases.
  • Movement disorders: B12 deficiency can also affect other parts of the nervous system involved in experiencing sensations or that allow the ability of nerves to conduct movement. Weakness and even complete inability to move limbs are associated with a B12 deficiency as well as an inability to feel sensation, vibration, or sense of where a limb is in space.
  • A loss of coordination and balance: This is also commonly associated with B12 deficiency. These symptoms may not occur with other signs and they may be the earliest or the most severe signs of disease.

Vitamin B12 deficiency quiz

Take a quiz to find out if you have vitamin B12 deficiency.

Take vitamin B12 deficiency quiz

Cardiovascular manifestations

It is important to note that there is not conclusive evidence that cardiovascular disease is caused by B12 deficiency. While there is an association between B12 deficiency and an increased risk of plaque buildup in the arteries, it is unclear whether this is caused directly by a B12 deficiency.

  • Chest pain and shortness of breath: This can develop in cases of severe anemia.
  • Hypoxia or a pale, bluish appearance: If there are insufficient healthy blood cells to carry oxygen from the lungs to the tissues, individuals may experience severe hypoxia (e.g. a low saturation of oxygen in the blood) and even a pale or bluish appearance.

Macular degeneration

Macular degeneration is a type of vision loss that occurs primarily in old age but is also associated with B12 deficiency. Over multiple years, it appears that B12 supplementation can lower the risk of macular degeneration. Macular degeneration is a leading cause of vision loss in the United States and is caused by deterioration of the center of the light-receiving part of the eye, the retina. It can be experienced by the following.

  • A wavy appearance of straight lines
  • A loss of the central vision
  • Difficulty focusing: The macula is important for many tasks that require focusing the eye, so reading, recognizing faces, driving and being mindful of driving signs may be impossible with advanced macular degeneration.


B12 deficiency contributes to an inadequate supply of functional blood vessels and an inability of the brain to properly communicate with muscles making movement difficult. More specifically, B12 deficiency can cause:

  • Weakness and fatigue from anemia
  • Paraplegia: This occurs via a loss of neurons in the spinal cord, which results in a loss of control the movement of the lower limbs and the perception of vibration, pressure, and individual limbs in space.
  • A difficulty with balance and coordination: The areas of the brain responsible for these actions are affected.

Causes of vitamin B12 deficiency

Causes of B12 deficiency can be related to inflammation of the stomach, effects of weight loss surgery, abiding by a vegan or vegetarian diet, medications, or malabsorption.

Inflammation of the Stomach (Atrophic Gastritis)

Atrophic gastritis is a type of inflammation of the lining of the stomach often called the gastric mucosa. It can affect different parts of the stomach and can be caused by either autoimmune processes in which the body's own immune cells attack the stomach or by inflammation caused by a pathogen (e.g. H pylori).

  • Autoimmune-related: The body's own immune cells target a special part of the stomach called the antrum near the top that produces a compound that allows for the absorption of B12 later on with digestion. The substance is called intrinsic factor, and without it, normal amounts of B12 are inadequate for digestion.
  • Pathogen-related: H pylori pathogens are more common causes but often does not affect the antrum. When it does, it is treated with antibiotics.

Weight loss surgery

During weight loss surgery, it is possible, though not uncommon, for the antrum to be damaged or even partially removed. A smaller stomach that can hold less food obviously restricts the amount of food an individual can consume. If the antrum is damaged it can severely reduce the ability to digest B12 and lead to a B12 deficiency.


Diets that contain very little or no animal products may not contain B12 in sufficient amounts to counteract the loss of B12 through normal daily activities, and over a long period of time, this can lead to B12 deficiency. It is important to supplement B12 in these cases with either a vitamin or with yeast which may have B12 depending on the type. In parts of the world where veganism or vegetarianism have existed for long periods of time, there is frequent B12 deficiency.


Medications for gastroesophageal reflux disease (GERD), if taken over a long period of time, can also cause a lack of B12 absorption. The most common medications include proton pump inhibitors and histamine-2 receptor blockers (or PPIs and H2 Blockers as they are more commonly known). These medications may interfere with the acidity of the stomach which separates B12 from the proteins that it is attached to and frees it to bind to carrying proteins within the stomach.


In the ileum of the gut, a later portion of the small intestine, vitamin B12 that is bound to intrinsic factor is absorbed. In conditions where the ileum is damaged, it is significantly more difficult to absorb vitamin B12. Surgery, intestinal resection, and inflammatory diseases affecting the ileum, particularly Crohn's disease, can cause a lack of ability to absorb B12, resulting in anemia and neurological signs.

Vitamin B12 deficiency quiz

Take a quiz to find out if you have vitamin B12 deficiency.

Take vitamin B12 deficiency quiz

Treatment options and prevention for vitamin B12 deficiency

B12 deficiency can be a mild condition with good outcomes if caught early and appropriately addressed. However, you should also be mindful of more concerning symptoms that can indicate serious complications.

Vitamin supplementation

The most successful treatment for vitamin B12 is vitamin supplementation if there is a problem with sufficient intrinsic factor. Supplementation can be done via oral vitamins or via intramuscular injection, but in early and moderate stage disease, supplementation can reverse defects. However, prolonged damage to the bone marrow or the nervous system can be permanent.

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When to seek further consultation for vitamin B12 deficiency

Treatment of vitamin B12 deficiency is essential because disease from a B12 deficiency is reversible if treated early enough. If it is not treated early enough it can lead to bone marrow failure, or an inability to produce enough types of blood cells to supply the body's needs, as well as demyelinating nervous system disease or permanent deficits in cognition.

At the first signs of the following, you should seek immediate medical care, especially if they are severe enough to interfere with your daily routine.

  • A loss of coordination
  • Uncharacteristic confusion
  • A loss or change of sensation
  • Chest pain
  • Lightheadedness
  • A loss of color (pallor)

Questions your doctor may ask to determine vitamin B12 deficiency

  • Do you have trouble sleeping?
  • Have you been feeling more tired than usual, lethargic or fatigued despite sleeping a normal amount?
  • How long has your current headache been going on?
  • Are you having difficulty concentrating or thinking through daily activities?
  • How severe is your headache?

Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.

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The stories shared below are not written by Buoy employees. Buoy does not endorse any of the information in these stories. Whenever you have questions or concerns about a medical condition, you should always contact your doctor or a healthcare provider.
Dr. Rothschild has been a faculty member at Brigham and Women’s Hospital where he is an Associate Professor of Medicine at Harvard Medical School. He currently practices as a hospitalist at Newton Wellesley Hospital. In 1978, Dr. Rothschild received his MD at the Medical College of Wisconsin and trained in internal medicine followed by a fellowship in critical care medicine. He also received an MP...
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