Some patients in your practice may actively self-advocate for their health goals. Alongside the patient’s involvement in their own well-being, recommending strategies to patients that can help them reach their wellness goals is beneficial. If conversations with your patients lead to discussions about supplementation, one option would be a vitamin B₁₂ supplement. Here’s guidance about vitamin B₁₂ supplementation to discuss with your patients in your primary care practice.

What Does Vitamin B₁₂ Do for the Body?

Vitamin B₁₂ provides important functions for the body. “B₁₂ plays a role in helping form red blood cells, as well as DNA,” said Jordan Faith, registered dietitian with UW Health in Madison, Wisconsin. “It also supports nerve and brain function.”

What Are Symptoms for Patients With Low B₁₂ Levels?

The most frequent symptoms include fatigue, anemia (often megaloblastic), loss of appetite, weight loss, and glossitis (inflamed tongue), said Jesus L. Lizarzaburu, MD, family physician at TPMG Grafton Family Medicine in Yorktown, Virginia. Also, neurologic manifestations are prominent and may precede hematologic (blood-related) findings; these include numbness or tingling in the hands and feet, impaired proprioception, gait disturbances, and neuropathy that can progress to chronic neuropathic pain and proprioceptive defects, he said.

Where Can Patients Find Natural Sources of B₁₂?

B₁₂ is naturally found in animal-based sources, such as clams, oysters, salmon, beef, milk, eggs, tuna, cheddar cheese, and turkey; it can also be found in fortified plant-based sources, such as fortified breakfast cereals and nutritional yeast, said Faith. The recommended dietary intake of B₁₂ as outlined by the 2020-2025 US Department of Agriculture’s Dietary Guidelines for Americans for adults is 2.4 µg/d. Needs may be increased during lactation and pregnancy.

Which Patient Populations May Benefit from B₁₂ Supplementation?

Recommending a B₁₂ supplement will vary on a patient-by-patient basis; however, checking B₁₂levels and repleting if there is deficiency could be considered. As a practitioner who works as a gastrointestinal dietitian, Faith has provided these guidelines regarding who may benefit from supplementation.

• People who are newly diagnosed with celiac disease may have impaired absorption of B₁₂ due to damage of the villi in the small intestine.
• People with short bowel syndrome who have the last part of their small intestine, the terminal ileum, removed; this is because the ileum is where B₁₂ is absorbed.
• People who are malnourished may not be consuming enough. She said dietitians (and other clinicians) can diagnose malnutrition based on diet history, weight history, and with a nutrition-focused physical exam.
• People following a vegetarian or vegan diet, as B₁₂ is mainly found in animal-based food sources. “While plant-based foods can be fortified with B₁₂, intake may be inadequate on a vegan or vegetarian diet,” said Faith.
• People who have had gastric bypass surgery or who have pancreatitis (especially chronic) are at risk for malnutrition and can have impaired absorption of B₁₂.
• People who have been on metformin or a proton pump inhibitor long term (> 2 years); both medications may impair absorption of B₁₂.
• Older adults are also a population who are at higher risk for deficiency of B₁₂.

What Are the Dosage Recommendations?

If a patient does not have any surgical or medical history that would impair absorption of B₁₂, but presents with B₁₂ deficiency, Faith recommends 1000 µg B₁₂ per day (in the form of cyanocobalamin) orally, with a plan to recheck complete blood count and B₁₂ levels in 3 months.

“Following restoration of B₁₂ levels, routine supplementation may be indicated in some individuals — specifically, those with low intake who follow a vegetarian or vegan diet or who have impaired B₁₂ absorption,” Faith said. Additionally, older adults are a population who are at higher risk for B₁₂ deficiency and may require routine supplementation.

Are There Any Drug Interactions With a B₁₂ Supplement?

Some medications may impair the absorption of B₁₂. This can occur due to the medication reducing gastric pH, affecting intrinsic factor production, which helps carry B₁₂ to be absorbed, or because of damage to the intestinal mucosa, said Faith.

Moreover, some of these medications include proton pump inhibitors, metformin, H2-receptor antagonists, and neomycin, she said. “Of note, a recent systematic review and meta-analysis noted more studies are needed to definitively link long-term use of proton pump inhibitors to B₁₂ deficiency, as current studies have had mixed results and have only looked at one biomarker,” Faith said.

Should Physicians Worry About B₁₂ Overconsumption?

Lizarzaburu said, “In my experience, it is extremely rare for someone to take too much vitamin B₁₂, and toxicity from high oral or parenteral intake has not been clearly established in medical literature.”

When Would You Recommend a B₁₂ Injection Over a B₁₂ Supplement?

The decision between supplementation or injection should be made based on an assessment of the patient’s symptoms and dietary intake. “I would recommend injections whenever the patient has developed neurologic symptoms, such as abnormal gait and numbness and tingling, along with a low level of vitamin B₁₂,” Lizarzaburu said. “Also, if the patient is found to be severely anemic because of vitamin B₁₂ deficiency, injections may be considered.” It’s important to note: studies show that oral supplementation is adequate, he said. “However, studies do not show any clear advantage to any form of oral supplementation,” Lizarzaburu said. “They all seem to work well.”