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Vitamin B12 deficiency can have many causes.

If you think you may be vitamin B12 deficient, please see our What to do next page for more information on your next steps.

The six most commonly identified causes of B12 deficiency are

  • An inability to absorb B12 from food. Please note, vitamin B12 is only found naturally in animal products.
  • A diet deficient in B12- for example, following a vegan or vegetarian diet.
  • Autoimmune pernicious anaemia.
  • A genetic defect (including MTHFR, MTRR)
  • Medications that hinder the body’s ability to use B12- for example metformin and acid suppressants. 
  • A secondary deficiency in a child, stemming from the mother being vitamin B12 deficient either prior to conception, during pregnancy or during nursing.

Below is a comprehensive list of potential causes of vitamin B12 deficiency

  • Toxic exposure
  • Decreased stomach acid
  • Atrophic gastritis
  • Autoimmune pernicious anaemia
  • Helicobacter pylori
  • Gastrectomy, partial or complete
  • Gastric bypass surgery (weight loss)
  • Intestinal resection
  • Partial or complete ileectomy
  • Gastrointestinal neoplasms
  • Malnutrition
  • Eating disorders  – anorexia – bulimia
  • Inadequate diet
  • Vegetarianism / veganism
  • Malabsorption syndromes
  • Alcoholism
  • Crohn’s disease
  • Coeliac disease (gluten enteropathy)
  • Diphyllobothrium infection
  • Blind loop syndrome
  • Diverticulosis
  • Inflammatory bowel disease
  • Small bowel overgrowth (SIBO)
  • Tropical sprue
  • Gastric irradiation
  • Ileal irradiation (bladder, cervix, uterus, prostate)
  • Inborn errors of B12 metabolism
  • Transcobalamin II deficiency
  • Pancreatic exocrine insufficiency & Chronic pancreatitis
  • Imerslund Gräesbeck syndrome
  • Zollinger – Ellison Syndrome
  • Bacterial overgrowth (small bowel)
  • Fish tapeworm
  • Advanced liver disease

Medicine / Drug induced causes – Please note this list is not exhaustive

  • Antacids
  • Colchicine – treatment of gout
  • H2 Blockers (Zantac, Tagamet, Pepcid)
  • Metformin – diabetes drug (Glucophage)
  • PPI’s – Proton pump inhibitors (Omeprazole, Nexium, Prevacid, Protonix)
  • Nitrous oxide anaesthetic
  • Nitrous oxide recreational abuse (laughing gas / whippets / hippy crack)
  • Levodopa – treatment of Parkinson’s
  • Mycifradin sulphate (Neomycin) – antibiotic
  • Para aminosalicylates – antibiotic
  • Phenytoin (Dilantin) – anti-epileptic
  • Potassium chloride (K-Dur)
  • Cholestyramine (Questran)
  • Chemotherapy and radiation treatment

Conditions which have an increased demand for B12…

  • Chronic haemoltic anaemia
  • Hyperthyroidism
  • Multiple myeloma
  • Myeloproliferative disorders
  • Neoplasms
  • Pregnancy

Personalised help…
If you would like personalised help either with reaching a diagnosis, or with receiving proper, effective treatment from your healthcare providers post-diagnosis, please see the Work with me page.

Who’s at risk?

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