Vitamin B12 deficiency

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at October 22, 2016
StartDiseasesVitamin B12 deficiency

Vitamin B12 helps the body produce healthy DNA and nerve and blood cells and is a crucial component in brain and immune system development. An estimated 15% of American adults don't get enough B12, often due to various factors concerning age, diet, and prescribed medications. Vitamin B12 is particularly difficult for some populations to get sufficient amounts of due to its existence only in animal products such as meat, shellfish, eggs, and dairy. The main warning signs of a B12 deficiency include prolonged periods of exhaustion, increased heart rate (tachycardia), and low mental stamina, along with other reoccurring symptoms.


Definition & Facts

The body's metabolism depends on B12, and oxygen-rich red blood cells rely on the vitamin for healthy reproduction. When the body doesn't receive enough of the B12 vitamin, the result is called vitamin B12 deficiency anemia, in which the body produces overly-large red blood cells that hinder internal functions, resulting in various outward symptoms that can affect one's health and well-being.

Vegetarians, vegans, those with frequent digestion problems or celiac disease, and adults over 50 are the most vulnerable to a vitamin B12 deficiency, with a reported 1 in 10 adults over 75 years of age experiencing symptoms.

While extremely rare, instances of low B12 levels can occur in infants fed on restricted diets free of animal products, or rely solely on breast milk provided by a vegan mother who does not take a vitamin B12 supplement. In such cases B12 supplementation can reverse the effects and prevent future deficiencies, though expecting mothers are encouraged to take prenatal vitamins fortified with B12 to eliminate the risk altogether.

Symptoms & Complaints

The symptoms of a vitamin B12 deficiency can vary in severity, from overwhelming to barely noticeable. Because the body is able to store vitamin B12 for three and sometimes even five years, early symptoms of a deficiency can be slow to appear, let alone diagnose.

Common complaints can include confusion, dizziness, brain "fogginess," and an overall feeling of fatigue or lack of energy. Shortness of breath, faintness, blurred vision, and chronic headaches can also occur, along with a slight ringing in the ears.

While a vitamin B12 deficiency often carries no outward or physical signs, some reports note a yellowing or paleness of the skin, as well as soreness of the tongue and mouth ulcers. In extreme cases mood swings, irritability, depression, and even dementia can occur.


Pernicious anemia (which literally translates as "dangerous" due to past fatality rates) is the most common cause of vitamin B12 deficiency. An autoimmune disease that occurs in roughly 1 in 10,000 people, pernicious anemia is brought on by an insufficient amount of protein necessary for absorbing vitamin B12.

Along with adults over 50, followers of strict vegan diets, in which little to no meat or dairy-derived protein is consumed, are also at risk for a vitamin B12 deficiency. Gastrointestinal diseases such as Crohn's disease and celiac disease can prevent metabolic absorption of B12, and some prescription medications, such as heartburn drugs, can suppress the production of peptic acids needed to absorb vitamin B12.

Researchers have found that prolonged consumption of medications used to treat heartburn, ulcers, and/or excessive stomach acid can carry a 25% increase in the likeliness of developing a vitamin B12 deficiency. Similarly, certain oral contraceptives high in estrogen can also hinder B12 absorption over extended periods of time. Because vitamin B12 is stored in the liver, excessive alcohol consumption can significantly deplete B12 amounts and further complicate the liver's ability to access them.

Certain weight loss procedures, such as gastric bypass surgery, can affect the gastrointestinal tract, making it more difficult for the body to absorb adequate amounts of B12. This is due to the sudden and considerable decrease in the body's ability to digest food, along with insufficient levels of intrinsic factor, a vital protein for absorbing B12 nutrients. Because this could be a permanent hindrance, people who undergo such procedures may be required to take vitamin B12 supplements regularly for the rest of their lives to avoid a deficiency.

Diagnosis & Tests

The best method for diagnosing a vitamin B12 deficiency is carried out through blood tests. The Centers for Disease Control and Prevention declares blood levels below 200 pg/mL (picograms/milliliter) to be indicative of a vitamin B12 deficiency.

A blood sample is taken by one's physician or nurse, and blood cells are examined beneath a microscope to determine hemoglobin levels, as well as the size of red blood cells. Folate levels are usually checked as well in order to detect the possibility of folate-deficiency anemia, which is commonly associated with a vitamin B12 deficiency.

Depending on the diagnosis, additional referrals may be made to various specialists, such as a hematologist (who specializes in blood conditions), a gastroenterologist (in case of a possible digestive disorder), or a nutritionist to help with necessary dietary adjustments.

Treatment & Therapy

If a vitamin B12 deficiency is detected, the treatment largely depends on the root cause of the deficiency. For example, if a diet containing inadequate amounts of meat or dairy products is the key culprit, a dietary physician may advise a nutritional overhaul. In other cases, routine B12 injections of hydroxocobalamin may be prescribed. 

Prevention & Prophylaxis

For many people, a vitamin B12 deficiency is often caused by diets lacking in meat, poultry, seafood, and dairy items such as milk, eggs, and cheese. Turkey, beef, trout, oysters, and salmon are particularly rich in B12, with a single serving of each delivering almost 100% of the daily recommendation.

Because vegan and vegetarian diets consist largely of plant-based foods such as veggies, fruits, beans, and soy products, the additions of B12-fortified foods such as breakfast cereals and whole grains, as well as vitamin B12 supplements, are important.

If taking an oral contraceptive or antacid medication, it's advisable to discuss possible precautions against B12 depletions with one's physician. For those who are over 50, it may be additionally worthwhile to add a daily supplement, as well as limit alcohol consumption.