For most hypothyroid patients, the most common B12 problem is due to being hypothyroid, which lowers stomach acid, then lowers absorption. Read more here.

But another B12 problem, even if less common than the above, is called Pernicious Anemia.

Pernicious Anemia is also low B12, but is usually the result of an autoimmune condition, meaning your body is attacking the parietal cells of the stomach lining. Parietal cells normally produce a protein termed an “intrinsic factor” which helps with the absorption of B12. But when the parietal cells are attacked, the levels of the intrinsic factor proteins are lowered, resulting in poor B12 absorption.

As a side note, Pernicious Anemia is part of a greater diagnosis called megaloblastic anemia, or having abnormally large red blood cells, which are actually immature red blood cells. So though large, they can be fewer, and ineffective. All because of the low B12 from Pernicious Anemia.

Other factors which can cause Pernicious Anemia and/or low B12 besides hypothyroidism

  • Pancreatic insufficiency (when the pancreas is making less digestive enzymes)
  • Gastritis (bacterial-caused inflammation which weakens the stomach lining)
  • Stomach Removal (whether partial from Bariatric Surgery, or complete removal)
  • Stomach cancer
  • Active mutation of the Q5R intrinsic factor gene, plus other genes
  • Low levels of folate aka B9

Symptoms of Pernicious Anemia

From The symptoms of pernicious anemia may include weakness, fatigue, an upset stomach, an abnormally rapid heartbeat (tachycardia), and/or chest pains. Recurring episodes of anemia (megaloblastic) and an abnormal yellow coloration of the skin (jaundice) are also common. 

Also included from the above link are shortness of breath, tingling and numbness of hands and feet, loss of appetite, diarrhea, unsteadiness when walking, bleeding gums, impaired sense of smell, and confusion. NOTE: the tingling and numbness of hands or feet can be from any cause of low B12, including hypothyroidism.

Tidbits of information about Pernicious Anemia

  • Low levels of folate can also lead to Pernicious Anemia and the red blood cell issue.
  • Most stats show that diagnosis is more common starting in the age 40’s, but especially in the 60’s or older.
  • Seems more common if you live in, or are from, northern Europe or Scandanavia. Northern Europe includes the British Isles, Denmark, Finland, Iceland, Norway and Sweden.


Most of the time, a medical professional will give or recommend B12 injections. But contrary to strong opinions from social media groups who say that injections are the only way to go for your lifetime, there are plenty of reports of patients doing well with B12 supplementation in higher doses, such as 2000mg or higher.


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