13 Sneaky Causes of B12 Deficiency

Updated: Sep. 05, 2018

A vitamin B12 deficiency, whether because you're not getting enough B12 or aren't absorbing it well, can cause symptoms like fatigue, difficulty walking, weakness, and confusion. Find out if you may be vulnerable to this condition.

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A vegetarian or vegan diet

Adopting a vegetarian or vegan diet delivers a lot of health benefits, but helping you maintain your B12 levels isn’t one of them. Keep in mind that the body can’t produce vitamin B12—you need to get the nutrient from the foods you eat. Alyssa Tucci, senior nutrition manager at Virtual Health Partners, points out that this vitamin is found almost exclusively in animal products, so plant-based diets can be one of the causes of B12 deficiency. She suggests incorporating supplemental B12 into your daily regimen if you’re a veggie to ensure that you’re meeting your needs.

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Intestinal trouble

As if those suffering from Crohn’s or celiac disease don’t have enough to contend with on a daily basis, a B12 deficiency could be another result of those conditions. “Under normal circumstances, vitamin B12 is absorbed in the intestines—as are most other nutrients,” explains Tucci. “Conditions that cause inflammation and damage to the small intestines, like Crohn’s and celiac disease, can impair our ability to absorb this important vitamin.” Find out the 10 ways B12 benefits your whole body, and why it’s so very important.

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We often think nothing of popping an antacid for a sour stomach or to combat acid reflux, but this seemingly innocent move can be one of the causes of B12 deficiency. “In order for B12 to be absorbed, you need to have adequate stomach acid,” says Andrea Maxim, ND. “Many people are taking acid blockers, which significantly reduce the amount of stomach acid you create.” According to Dr. Maxim, when this acid is created, the stomach releases a protein called intrinsic factor that helps the intestine absorb B12. When you reduce stomach acid with antacids, “the release of intrinsic factor becomes impaired, and therefore B12 can’t get absorbed.”

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Common prescription drugs

It’s not just over-the-counter antacids that can cause B12 trouble; Yaffi Lvova, RDN, of Baby Bloom Nutrition, points to prescription medications such as methotrexate (used to treat psoriasis, rheumatoid arthritis, and some cancers), certain antibiotics, and some cholesterol-lowering drugs as causes of B12 deficiency. Check out these 22 warning signs your vitamins aren’t going to work.

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A 2013 study published in the Journal of Diabetes and Metabolic Disorders revealed that patients with type 1 and type 2 diabetes are at high risk for B12 deficiency. Metformin, a common treatment for type 2 diabetes, is the connection—it is another prescription medication that seems to interfere with B12 absorption.

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Oral contraceptives

In a 2013 study published in the journal Nutrients, a team set out to learn whether or not oral contraception was one of the causes of B12 deficiency in women. They concluded that, yes, hormonal contraception does cause B12 levels to decrease, although “not enough to be clinically significant.” With that being said, the study examined  only one formula of birth control, and, as Scientific American points out, since contraception is usually taken over long periods of time, subtle effects of B12 depletion can add up. Make sure you know these 11 silent symptoms of B12 deficiency.

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Weight-loss surgery

Bariatric surgery is yet another choice that may otherwise be healthy but that can also be one of the causes of B12 deficiency. “If someone has had weight-loss surgery involving removal of part of the stomach, that could cause a deficiency,” Lvova says. “These individuals are prescribed vitamins specific to their experience, often including a form of B12 that bypasses the digestive tract and goes straight into the bloodstream.”

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According to estimates from the National Health and Nutrition Examination Survey, one in 33 adults over the age of 50 have very low B12 levels, and up to 20 percent may be borderline deficient. As with so many aspects of our health, production of stomach acid declines as we get older. Like it or not, says Tucci, it’s a natural part of aging. This is why doctors may prescribe a supplement to people as they get older.


Atrophic gastritis

Gastritis is an inflammation of the stomach lining, according to the Mayo Clinic. Bacterial infections, regular use of pain relievers, and stress—among other things—can all contribute to the condition. It is also one of the causes of B12 deficiency.

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Pernicious anemia

With this autoimmune condition, the body’s defense mechanisms actually attack the healthy cells in the stomach that produce intrinsic factor—the protein you need to absorb B12. (Low B12 levels may also bring on pernicious anemia.) According to the National Heart, Lung, and Blood Institute, “Without intrinsic factor, your body can’t move vitamin B12 through the small intestine, where it’s absorbed. This leads to vitamin B12 deficiency.”

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Other autoimmune disorders

When your immune system goes haywire and begins attacking healthy tissues in your body, you have an autoimmune condition. You already know that pernicious anemia can be a cause of B12 deficiency; chronic urticaria, a condition characterized by welts developing on the skin, may also be a trigger, along with thyroiditis, an inflammation of the thyroid that can lead to hypothyroidism. Find out what you need to know about habits that lower immunity.

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H. pylori infection

This is the bacteria behind certain types of ulcers—and anything that causes trouble for your tummy can also be a cause of B12 deficiency. According to the Mayo Clinic, nearly half of the entire world’s population may have H. pylori. Check out these 12 vitamin mistakes you may not realize you’re making.

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Is there any condition where stress doesn’t somehow make things worse? Stress exacerbates ulcers and bumps up stomach acid production (which can lead sufferers to overuse antacids). Need some ways to relax? Check out these 37 expert tips for de-stressing in a hurry.