Understanding Who is Most Likely to be Vitamin B12 Deficient

October 19, 2025 •

3 min read

According to the National Institutes of Health, between 3% and 43% of community-dwelling older adults may have a vitamin B12 deficiency, primarily due to malabsorption issues. This guide explores who is most likely to be vitamin B12 deficient, examining the key risk factors and how to manage them through informed nutritional choices and medical supervision.

Quick Summary

Several factors, including age, diet, medical conditions like pernicious anemia, and certain medications, can increase an individual's risk of developing a vitamin B12 deficiency.

Key Points

Older adults: Individuals over 65 are highly susceptible due to decreased stomach acid and malabsorption, often caused by atrophic gastritis.
Vegans and Vegetarians: This group is at risk because B12 is naturally found in animal products; regular supplementation or fortified foods are essential for prevention.
Pernicious Anemia: An autoimmune disease where the body cannot produce intrinsic factor, a protein needed for B12 absorption, requiring lifelong supplementation.
Gastrointestinal Disorders: Conditions like Crohn's, Celiac disease, and chronic gastritis can interfere with the body's ability to absorb B12 effectively.
Gastric Surgery Patients: Procedures like gastric bypass can permanently alter the digestive tract, necessitating lifelong B12 supplementation.
Medication Users: Certain long-term medications, including proton pump inhibitors (PPIs) and metformin, can reduce B12 levels.
Subtle Symptoms: B12 deficiency symptoms, such as fatigue, nerve issues, and cognitive problems, can be subtle and develop gradually over time.
Early Detection is Crucial: Because some neurological damage from B12 deficiency can be irreversible, early diagnosis and treatment are vital.

The Role of Vitamin B12 in Your Body

Vitamin B12, or cobalamin, is an essential water-soluble vitamin that plays a critical role in numerous bodily functions, including nerve cell and red blood cell health, DNA synthesis, and energy production. Since the human body doesn't produce B12, it must be obtained from food. While dietary intake is a factor, particularly for those avoiding animal products, malabsorption in the digestive system is the most common cause of deficiency. The liver stores a significant amount of B12, so a deficiency can take years to appear after intake or absorption problems begin.

Major Groups at Risk of Vitamin B12 Deficiency

Older Adults

Older adults are frequently at risk due to age-related digestive changes. A common issue is atrophic gastritis, which reduces stomach acid needed to release B12 from food for absorption. This affects absorption even with adequate B12 consumption, becoming more prevalent in those over 65.

Vegans and Vegetarians

Vegans and strict vegetarians face a high risk because B12 is mainly found in animal products. While some plant foods are fortified, reliable B12 intake typically requires regular supplementation or consistent consumption of fortified foods to prevent depletion over several years. Infants breastfed by vegan mothers who don't supplement are also at risk.

Individuals with Pernicious Anemia

Pernicious anemia is an autoimmune condition where the body attacks cells that produce intrinsic factor, a protein essential for B12 absorption. This prevents proper absorption of B12 from the diet and requires lifelong treatment with injections or high-dose oral supplements.

Patients with Gastrointestinal Disorders

Chronic conditions affecting the stomach and small intestine can impair B12 absorption. These include Crohn's disease (affecting the primary absorption site), Celiac disease (damaging the small intestine lining), chronic gastritis and H. pylori infection (reducing stomach acid and intrinsic factor), and exocrine pancreatic insufficiency.

Post-Surgical Patients

Gastric surgeries, especially weight-loss procedures like gastric bypass or removal of part of the stomach, significantly increase the risk. These procedures alter the digestive tract, affecting intrinsic factor production and B12 absorption, making lifelong supplementation necessary.

People Taking Certain Medications

Some long-term medications interfere with B12 absorption. This includes Proton Pump Inhibitors (PPIs) and H2 blockers, which reduce stomach acid needed to release B12 from food, and Metformin, a diabetes drug that can lower B12 levels.

Chronic Alcohol Users

Long-term, excessive alcohol use can damage the digestive system, leading to poor B12 absorption.

Comparison of Risk Factors


Risk Factor	Primary Mechanism of Deficiency	Onset of Symptoms	Management Approach
Older Adults	Decreased stomach acid due to atrophic gastritis leading to malabsorption.	Gradual onset, can take years.	Diet rich in fortified foods and supplements; potential lifelong supplementation.
Vegans/Vegetarians	Inadequate dietary intake from animal products.	Can take several years due to liver stores; dependent on dietary choices.	Consistent B12 supplementation or regular consumption of fortified foods.
Pernicious Anemia	Autoimmune destruction of cells producing intrinsic factor, leading to severe malabsorption.	Gradual but progressive and irreversible.	Lifelong intramuscular injections or high-dose oral supplements.
Gastric Surgery	Removal or bypass of stomach or intestine sections responsible for intrinsic factor and absorption.	Depends on pre-surgery B12 reserves, but can occur years after.	Lifelong supplementation, often through injections or high-dose oral forms.
Certain Medications	Interference with stomach acid production or the absorption process in the intestine.	Long-term use is associated with gradual decline in B12 status.	Monitoring B12 levels; adding supplements if deficiency develops.

Recognising the Symptoms

B12 deficiency symptoms can be subtle and slow to develop. Common signs include fatigue, weakness, pale skin, a sore tongue, mouth ulcers, numbness or tingling, balance issues, memory problems, confusion, mood changes, and vision problems.

The Importance of Professional Medical Guidance

If you are in a high-risk group or notice symptoms, consult a healthcare provider. A blood test can check B12 levels, and high-risk individuals should consider routine screening. Avoid self-treating with high-dose supplements without medical advice, as this can mask underlying conditions.

Conclusion

Vitamin B12 deficiency is often caused by absorption problems, not just diet. Those most at risk include older adults, vegans, individuals with autoimmune or gastrointestinal issues, post-gastric surgery patients, and those on certain medications. Since symptoms can be subtle, awareness and proactive management with medical guidance are crucial for preventing serious complications. For more information, consult resources from reputable health organizations.

NIH Office of Dietary Supplements

Frequently Asked Questions

Early signs often include fatigue, lack of energy, and feeling weak. Other initial symptoms can be pale skin, a sore mouth or tongue, and mood changes like irritability or depression.

No, natural food sources of vitamin B12 are exclusively animal-based. Vegans and vegetarians must get their B12 from fortified foods, such as cereals and plant milks, or from dietary supplements.

As people age, their bodies often produce less stomach acid. Since stomach acid is needed to release vitamin B12 from food for absorption, this can lead to a deficiency, even with a B12-rich diet.

Yes. Pernicious anemia is a lifelong autoimmune condition that prevents the body from absorbing B12. It requires ongoing treatment, typically with injections or high-dose oral supplements, to maintain adequate B12 levels.

Certain long-term medications can interfere with B12 absorption. Common examples include metformin for diabetes, and proton pump inhibitors (PPIs) and H2 blockers for acid reflux.

For most people with a dietary B12 deficiency, high-dose oral supplements can be as effective as injections. However, in cases of severe malabsorption (like pernicious anemia), injections are often necessary because they bypass the intestinal absorption process entirely.

The human body stores a significant amount of vitamin B12, mainly in the liver. It can take several years for a deficiency to manifest after intake or absorption decreases. This is why awareness is crucial, especially for those in high-risk groups.