Are You at Risk for Vitamin B12 Deficiency?

Low blood levels of this important vitamin can have serious consequences over time.


If you’ve noticed you’re feeling a bit more tired and weak and your brain isn’t working as well as it used to, don’t just chalk it up to getting older. In some people, these symptoms can be due to years of low intake or poor absorption of vitamin B12. Luckily, the effects of B12 deficiency can be reversed if caught early enough.

B12 Basics. Also known as cobalamin, vitamin B12 is necessary for the production of red blood cells and DNA and the proper functioning of the nervous system. Vitamin B12 is classified as an essential nutrient: the body doesn’t make it, so we must get it from diet. This nutrient is only found naturally in animal foods, including liver, seafood (such as clams, salmon, and other fish), dairy products, meat, poultry, and eggs. Certain plant-based foods, such as breads, cereals, tofu, and plant milks, sometimes have vitamin B12 added to them (check the Nutrition Facts label to be sure). Additionally, some bacteria used in fermentation processes produce vitamin B12, so fermented foods like yogurt, kefir, tempeh, miso, kimchi, sauerkraut, and pickles are good sources of this vitamin (just beware of high sodium content in some of these foods).

Dangerous Deficiency. Vitamin B12 deficiency can lead to symptoms such as anemia, weakness, fatigue, numbness or tingling in the hands and feet, unsteady walking or balance issues, and cognitive difficulties like memory loss. Unlike most water-soluble nutrients, the liver can store three to five years’ worth of this essential nutrient, so symptoms may appear gradually and worsen slowly over time. This means inadequate vitamin B12 intake or absorption can go undetected for years. When symptoms do emerge, they are often mistaken for signs of other conditions. Cognitive difficulty caused by B12 deficiency, for example, could be misdiagnosed as new onset of Alzheimer’s or other dementia.

Symptoms can be reversed with early detection and treatment. But left untreated, damage can be permanent. When suspicious symptoms are present, “B12 deficiency should always be ruled out,” says Andrew G. Plaut, MD, a gastroenterologist at Tufts Medical Center. “The consequences of advanced deficiency can be severe, such as causing pernicious anemia—a decrease in red blood cells—paralysis, and even nerve damage.”

Individuals who follow strict vegan diet patterns or other restrictive diets for long periods of time are at higher risk for inadequate B12 intake, but vitamin B12 deficiency is rarely caused by dietary shortfalls alone. “Most B12 deficiency is from issues in the stomach or intestine which prevent absorption,” says Plaut. Individuals who have had surgery on the stomach or small intestines (including gastric bypass surgery) or have conditions that interfere with nutrient absorption—such as Crohn’s disease, celiac disease, or small intestinal bacterial overgrowth (SIBO)—are at increased risk for B12 deficiency. Since stomach acid plays an important role in preparing vitamin B12 for absorption, long-term use of acid-reducing medications like proton-pump inhibitors (PPIs) and H2 blockers may increase risk for low vitamin B12 levels. Older adults can also be at higher risk of deficiency because stomach acid production may decrease with age.

What to Do. For most people, a varied diet that includes occasional animal products (fish, eggs, cheese, yogurt, meat) or fortified foods provides more than enough vitamin B12. The daily recommended intake is 2.4 micrograms, about the amount in three ounces of tuna or a half-cup of fortified cereal. If you suspect you are at risk of deficiency, talk to your healthcare provider about assessment and monitoring. A routine complete blood count (CBC) may show abnormal red blood cells if you’re very low on vitamin B12, but the most sensitive blood test—one that measures vitamin B12 levels—must be ordered separately. Different forms of supplements are effective at reversing deficiency, but it is critical to determine the cause of the deficiency before establishing the best route of administration (pills, nasal spray, or injection). Getting a proper diagnosis from your healthcare provider is essential.

Take Charge!

Try these tips to avoid long-term dangers of vitamin B12 deficiency:

  • Identify risk. Certain individuals, such as vegans, older adults, people taking acid reducing drugs for many years, and those with absorption disorders, are at higher risk for vitamin B12 deficiency.
  • Know the symptoms. Alert your healthcare provider if you experience symptoms such as fatigue, weakness, numbness of the hands or feet, difficulty walking, or new onset of cognitive difficulties.
  • Get checked out. A blood test for vitamin B12 deficiency has to be ordered. Routine blood work might reveal pernicious anemia when there is a serious deficiency.
  • Eat a varied diet. Most people get adequate B12 from occasional animal foods and fortified and fermented foods.


  1. One of the recommendations is to consume “occasional” animal foods. An ambiguous term like “occasional” isn’t helpful because it can mean different things to different people.


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