What’s the Difference between Vitamin B12 Deficiency and Pernicious Anaemia?

Pernicious Anaemia is the most common cause of Vitamin B12 Deficiency1 but it is not the only reason for patients becoming deficient in this vitally important vitamin.

Vitamin B12 Deficiency

Vitamin B12 Deficiency is a worldwide problem. ‘In the United Kingdom and United States the prevalence of vitamin B12 deficiency is around 6% in people aged less than 60 years, and closer to 20% in those aged more than 60 years2. One author has calculated that nearly 6 million people in the UK are deficient, whilst the figure for the USA is over 26.5 million. In India over 586,000,000 people are deficient in the vitamin.3

However, these figures need to be treated with caution, not because they may be exaggerated but quite the opposite; they are probably an understatement.
This is because of four major problems.
Firstly, nearly 40% of members of the Pernicious Anaemia Society had their deficiency wrongly diagnosed – the symptoms were attributed to some other illness.
And so that means that there are probably many millions of people who are feeling ill but who have yet to be told that they are B12 deficient.4
vitamin b12
Secondly, there is no consensus amongst scientists as to what levels constitute a deficiency and this is further complicated by the fact that different countries and different areas within countries UK will have different thresholds used to determine a deficiency. That means that in one particular part of a country you will be told your B12 levels are ‘normal’, yet if you lived in another part of the country you might be identified as being deficient. Some scientists believe even the highest thresholds that are used to define a deficiency are far too low. 5
Thirdly, there is the tricky issue of ‘sub-clinical deficiency’ where the patient’s serum B12 might be above the threshold used to define a deficiency yet he or she will have all of the symptoms of a deficiency in the vitamin.
Finally, there is now widespread acknowledgement that the machines used to determine the amount of B12 in patients are seriously flawed and give false high readings in many cases.6
All of the above make the task of diagnosing patients as being deficient in vitamin B12 often very difficult.

Vitamin B12: What Is It And What Does It Do?

Vitamins are essential nutrients, necessary for the proper functioning of our body. They can be divided into the fat-soluble vitamins A, D, E and K, and the water-soluble vitamin C and all B vitamins.

Vitamin B12 is also known as cobalamin. At the center of vitamin B12 is a metal: cobalt, hence the name cobalamin. The natural forms of vitamin B12 that occur in our diet are: methyl-, hydroxy- and adenosylcobalamin.

Vitamin B12 is essential for all kinds of systems in the body, including the health of the nervous system, the immune system, the cardiovascular system and the gastrointestinal system. If there is not enough vitamin B12 present in the body, because it is not properly absorbed or because too little comes in, these systems will work less well, resulting in all kinds of symptoms.

Causes of B12 Deficiency

There are many ways in which people can become deficient in Vitamin B12.

1. Diet

Vitamin B12­ is found only in foods that are animal based with the exception of seaweed (Laver Bread in Wales and Nori in Japan). Consequently, people who do not eat animal products run the risk of becoming deficient in B12. Those who exclude meat from their diet but do eat fish and dairy will be much less at risk of developing a deficiency because dairy products make B12 ‘more bioavailable’.

2. Gastric Atrophy (Atrophic Gastritis)

Atrophy is the medical word used to describe ‘wasting away’. Gastric Atrophy is the result of chronic inflammation of the stomach lining which means it cannot produce hydrochloric acid (needed to break down food), pepsin (that helps speed up the break-up of food) or Intrinsic Factor which is necessary to help ‘extract’ B12 from food. Atrophic Gastritis can be caused by advancing age, by Helicobacter Pylori or by Autoimmune Gastritis where the patient produces antibodies that destroy either the Parietal Cells or Intrinsic Factor or both.

Vitamin B12 Absorption

3. Intestinal diseases and infections

  • Crohn’s disease
  • Celiac disease
  • Chronic pancreatitis
  • Intestinal bacterial overgrowth
  • Fish Tapeworm (Diphyllobothrium)
  • Giardiasis (or Beaver Fever)
  • Tropical sprue
  • Intestinal lymphoma
  • Amyloidosis
  • Short bowel syndrome

4. Surgery

  • Gastic bypass
  • Partial gastrectomy
  • Ileal resections
  • Surgical Anastomosis

5. Medication

The following leads to the patient’s B12 being compromised in some way and to some degree or other:

  • Metformin (Type 2 Diabetes)
  • Proton pump inhibitors (PPIs), such as omeprazole, lansoprazole, and esomeprazole, and H2-receptor antagonists, such as ranitidine, cimetidine, famotidine, and nizatidine
  • Oral contraceptives (although suggested this is more redistribution than causing actual functional deficiency)
  • Colchicine (used to treat gout)
  • Cimetidine (used to treat peptic ulcers)
  • Phenobarbital, Pregabalin, Primidone and Topiramate (epilepsy)

WARNING: You should never stop taking your medication before talking to your doctor.

7. Nitrous Oxide (Laughing Gas) (N2O)

Now the UK’s second most recreational drug after marijuana. Also used in (dental) surgery and in Gas & Air. Deactivates the bodies stores of Vitamin B12.

8. Inborn errors in the transport or metabolism of vitamin B12

Transcobalamin deficiency, adenosylcobalamin deficiency (cblA, cblB, mut), methylcobalamin deficiency (cblE, cblG), combined adenosylcobalamin and methylcobalamin deficiency (cblC, cblD, cblF, cblJ).

  1. Andres E, Serraj K. Optimal management of pernicious anemia. Journal of Blood Medicine 2012; 3:97-103
  2. Hunt A, Harrington D, Robinson S.; Vitamin B12 Deficiency; British Medical Journal 2014; 349:5226
  3. Hooper M. What You Need to Know About Pernicious Anaemia and Vitamin B12 Deficiency; Hammersmith Health Books, London; 2014.pp 32-34
  4. Hooper M, Hudson P, Porter F, McCaddon A; Patients Journeys; the diagnosis and treatment of pernicious anaemia; British Journal of Nursing 2014; 23;7;385-386
  5. Smith D, Refsum H. Do we need to reconsider the desirable blood level of vitamin B12?; Journal of Internal Medicine 2011; 271(2):179-182
  6. Carmel R, Agrawal Y; Failures of cobalamin assays in pernicious anaemia; New England Journal of Medicine 2012; 367;4:385-386
  7. R. Ahmadi & Dominic J. Harrington (2021): Vitamin B12 status in health and disease: a critical review. Diagnosis of deficiency and insufficiency – clinical and laboratory pitfalls , Critical Reviews in Clinical Laboratory Sciences, DOI: 10.1080/10408363.2021.1885339

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