What causes vitamin b12 deficiency?

What causes vitamin b12 deficiency?

by Jigar Parmar on Jan 27, 2023

  • Almost half of the indian population suffer from vitamin b12 deficiency.
  • As we know, Inadequate diet causes nutritional deficiency. But, furthermore some conditions and diseases are also the reason for such nutritional ( vitamin b12 ) deficiency.
  • Causes of B12 deficiency can be related to nutritional deficiency due to strict vegan or vegetarian diet, inflammation of the stomach (gastritis), malabsorption, medications, post - surgery efect on body, habitual alcoholism, diabetes mellitus

Plenty of conditions can set the stage for vitamin B12 deficiency :

  • Hypoclorhydria Inability to Produce Hydrochloric Acid in stomach: hydrochloric acid helps separate vitamin B12 from protein so it can be absorbed.
  • Lack of Intrinsic Factor: a protein in the stomach that bonds with vitamin B12 to help the body properly absorb the vitamin b12.
  • Pernicious Anemia: a specific (autoimmune) type of megaloblastic anemia that doesn’t allow the body to properly absorb vitamin B12, which can lead to other symptoms and health problems down the road.
  • Stomach/​Intestinal Disorders: diseases such as malabsorption,Crohn’s or celiac disease, chronic diarrhoea can make it difficult to absorb sufficient vitamin B12 in small intestine.


1. Strict Veganism or Vegetarianism:

  • 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 treat vitamin B12 deficiency with either a vitamin b12 supplements or by removal of cause like  inflammation, malabsorption etc.
  • In parts of the world where veganism or vegetarianism have existed for long periods of time, there is frequent B12 deficiency.
  • Although, there is good source for vitamin b12 in vegan or vegetarian diet, you can check out for more info (link to blog)


2. 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 H-pylori bacteria.
  • Autoimmune-related: The body's own immune cells target the stomach inner layer and The substance called intrinsic factor get destroyed, and without it, normal amounts of B12 are inadequate for digestion.
  • infection-related: H pylori bacteria are more common causes of gastritis, which are too difficult to cure and this complaint occurs nearly 3 to 4 times a year.
  • This H.pylori bacteria infection is treated with antibiotics, and you will get relief of abdominal pain and heaviness but it tends to releps in later in the year.


 3. Malabsorption:

  • In the ileum of the gut a later portion of the small intestine, the vitamin B12, who is binded  to intrinsic factor are get absorbed. In the 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 vitamin B12, resulting in anemia and neurological signs.


4. Medication:

  • Medications for gastroesophageal reflux disease (GERD -known as acidity, abdominal pain and regurgitation of food or sour fluid in mouth) 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 protein - intrinsic factor within the stomach. 

  • Also there are list of medication which are interfering with vitamin b12 absorption you can check (blog link)


5. Major surgery:

  • Surgery produces stress in body, thus its more prone to get ill-effect on stomach, decreased appetite, indigestion, malabsorption, stress ulcers etc,
  • Further more specific on During weight loss surgery, it is possible, though not uncommon, for the antrum (stomach part) 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.


6. Habitual alcoholism:

  • The bad habit of drinking alcohol ( daily more than 50ml ) causes damage to your liver and malabsorption of nutrients through the small intestine. it will lead to weight loss, diarrhoea, and osteoporosis.
  • Alcohol causes metabolic disturbance in the liver thus, it leads to fatty liver or cirrhosis of the liver.

Malabsorption of the body's required nutrients like vitamins, carbs, protein, fats, and electrolytes leads to weakness and weight loss and the body needs additional multivitamin supplements to maintain health.


7. DM:

  • Diabetes mellitus is a condition in which body does not control proper amount of sugar in blood and leads to consequences of hyperglycemia like a polyphagia, polydipsia, and polyuria.
  • In our body homoeostasis is maintained for our health, as the amount increases than the body increases the amount of water to maintain blood composition.
  • Gi system disturbs due to increased sugar and water content in blood, which leads to increased gastric motility - diarrhoea, bacterial overgrowth - infections, kidney damage etc.
  • Thus with such altered health conditions and common drug for dm metformin which decreases vitamin b12 absorption, a person has to monitor increased vitamin b12 requirement. 



  • Illness, altered health, or any diseases directly or indirectly affects gestro-intestinal system and leads to indigestion and malabsorption of essential vitamins like vitamin b12.
  • So, if you are dealing with such a given cause in life then you have to monitor your vitamin b12 in your body and the increased requirement of vitamin b12 to maintain your healthy life.