Vitamin B12 Deficiency: 2 RCCA Hematologists Explain Its Causes, Risks, and Treatment


Sometimes, a vitamin deficiency can be corrected simply by eating more leafy green vegetables or taking a daily supplement. In the case of significant Vitamin B12 deficiency, however, a shot in the arm may be just what the doctor ordered – literally.

Vinod Varki, MD, explains, “Up to 95% of American adults have some degree of vitamin deficiency, with inadequate levels of Vitamins D, E, C, and A being the most common, in that order. Vitamin B12 deficiency is seen less often, but low levels of B12 require treatment to avoid potential problems including fatigue, neurological issues, heart palpitations, and low counts of the red blood cells that carry oxygen and the white blood cells that fight infection.”

Dr. Varki, a board-certified medical oncologist and hematologist, adds that the prevalence of Vitamin B12 deficiency increases with age. “Research indicates that 3% or less of U.S. adults age 39 or younger have inadequate levels of B12, while that percentage climbs into the double digits among people aged 60 years or older, reaching 14% or even higher depending on the blood-level cutoff used to define deficiency,” says Dr. Varki, who practices in the Riverdale, NJ, office of Regional Cancer Care Associates (RCCA), one of the nation’s largest networks of oncology specialists. RCCA offers care at more than 20 locations near you in New Jersey, Connecticut, Massachusetts, and the Washington, D.C., area.

Aging and the Risk of Vitamin B12 Deficiency

Ian Horkheimer, MD, notes that the increase in Vitamin B12 deficiency seen with age is due, in large part, to the fact that three conditions that contribute to the deficiency are more common in older people. Dr. Horkheimer, a board-certified medical oncologist and hematologist who practices at RCCA’s Little Silver, NJ office, explains, “The first of these conditions is pernicious anemia. This is an autoimmune disease that affects the lining of the stomach, causing malabsorption of dietary B12. The second condition is atrophic gastritis, another autoimmune disease that affects 8% to 9% of older adults. This form of gastritis decreases the body’s production of a substance called intrinsic factor and reduces secretion of hydrochloric acid, impairing absorption of Vitamin B12. Third, Helicobacter pylori infection can cause inflammation, potentially leading to malabsorption of the vitamin.”

Other Risk Factors for Vitamin B12 Deficiency

Beyond older age, Dr. Horkheimer notes that several other factors can place a person at elevated risk for Vitamin B12 deficiency. He adds, “These risk factors can be divided into three broad categories. The first is inadequate intake of foods containing B12. This can be an issue for people who follow a strict vegetarian diet and for people who eat a lot of ultra-processed foods. The second category is inadequate absorption of B12 from foods containing the vitamin. Absorption issues can affect people with heavy alcohol use or gastrointestinal disorders such as Crohn’s disease, as well as people who have had bariatric procedures and other gastrointestinal surgeries. Third, use of some medications, such as metformin or proton pump inhibitors, or exposure to substances such as nitrous oxide, can cause a B12 deficiency.”

Why Diagnosing and Correcting Vitamin B12 Deficiency Matter

Dr. Varki notes that adequate levels of Vitamin B12 are critical for the development and function of the nervous system, the formation of healthy red blood cells, and the production of DNA, the genetic foundation of cells and of life itself.

“The wide-ranging roles that Vitamin B12 plays explain why a significant deficiency of the vitamin can lead to a host of symptoms. Fortunately, the more extreme symptoms – such as vision problems or developing ulcers in the mouth – are uncommon. However, fatigue, loss of appetite, cognitive problems, numbness or tingling in the hands and feet, and even feeling depressed or irritable, all can occur when B12 blood levels fall,” the hematologist says.

Dr. Varki continues that while measuring serum levels of Vitamin B12 is not part of the annual physical examination for people who don’t have risk factors for a deficiency, blood work is a key component of the evaluation when a patient has symptoms suggestive of the condition.

“Let’s say that a patient sees his or her primary care physician and reports experiencing fatigue. That is a relatively common complaint, and one that can be the result of a great number of conditions, some more serious than others. The physician will start by taking a thorough history. Factors such as having Crohn’s disease or ulcerative colitis, significant alcohol use, or following a vegetarian diet would focus the physician’s attention on a potential deficiency of Vitamin B12, along with several other possible causes,” Dr. Varki notes.

The hematologist adds that the physician would ask about other symptoms that might suggest inadequate levels of B12 and perform a physical examination to look for signs of that condition or other disorders. Initial blood tests would include a complete blood count (CBC) and measurement of serum levels of B12 and folate, also known as Vitamin B9, which has many functions similar to those of B12. Dr. Varki notes, “When there is a significant Vitamin B12 deficiency, the CBC often will show large, structurally abnormal, under-developed red blood cells, which is known medically as megaloblastic anemia.”

Dr. Horkheimer says that once Vitamin B12 deficiency is identified, the focus turns to addressing underlying causes, when possible, and to providing treatment to help the patient achieve adequate levels of the vitamin.

“Some underlying causes can be modified, such as reducing alcohol use, increasing intake of food containing Vitamin B12, and perhaps changing prescriptions when a particular medication interferes with absorption of the vitamin. Daily high-dose oral supplements also can help correct a mild deficiency or one driven by diet. However, other causes, such as pernicious anemia, cannot be corrected,” he says.