Understanding Nutritional Health: Is B12 Deficiency Common and What Causes It?

October 28, 2025 •

3 min read

According to data from the National Health and Nutrition Examination Survey (NHANES) from 2007–2018, approximately 3.6% of US adults aged 19 and older have a vitamin B12 deficiency, with rates of insufficiency being much higher. This raises the critical question: Is B12 deficiency common? The answer is complex, as prevalence varies significantly based on age, diet, and underlying health conditions, making a blanket assumption misleading.

Quick Summary

This article explores the prevalence of vitamin B12 deficiency, detailing how its commonness differs across demographics like age and diet. It identifies key risk factors such as dietary choices, medical conditions, and certain medications, and explains the absorption process. The piece covers a wide range of symptoms and outlines standard diagnostic and treatment approaches.

Key Points

Variable Prevalence: The commonness of B12 deficiency varies significantly, affecting up to 20% of older adults in some developed nations and much higher percentages in developing regions.
Older Adults at Risk: Declining stomach acid production with age impairs the absorption of food-bound B12, making older adults a major risk group.
Beyond Dietary Intake: Malabsorption due to gastrointestinal issues like Crohn's disease, pernicious anemia, and bariatric surgery is a leading cause, not just poor dietary intake.
Subtle Symptoms: Early symptoms like fatigue and weakness are often overlooked, which can lead to delayed diagnosis and potential neurological damage.
Screening is Crucial: Regular screening with blood tests is recommended for high-risk groups, including vegans and the elderly, to catch deficiencies early.
Diverse Treatment Options: Treatment can be managed with high-dose oral supplements for many, while injections are used for severe cases or specific malabsorption issues.

The Surprising Prevalence of Vitamin B12 Deficiency

Vitamin B12 deficiency is a relatively common issue worldwide, though often underestimated due to subtle, gradual symptoms. In developed countries, about 6% of the general population may be deficient, with this number rising to nearly 20% in those over 60 years old. The prevalence is considerably higher in developing countries, where deficiency rates can reach 40-70%, particularly in populations consuming diets low in animal products.

Why Absorption, Not Just Intake, is Critical

Impaired absorption is the most frequent cause of B12 deficiency. The vitamin needs stomach acid to be released from food and intrinsic factor to be absorbed in the small intestine. Problems at any stage of this process can lead to deficiency, even with adequate intake.

Key Risk Factors for Developing a B12 Deficiency

Certain groups are more vulnerable to B12 deficiency:

Older Adults: Reduced stomach acid (atrophic gastritis) common in older age hinders B12 release from food.
Vegans and Vegetarians: Vitamin B12 is primarily found in animal products, placing those on strict plant-based diets at high risk without fortified foods or supplements.
Individuals with Gastrointestinal Disorders: Conditions like Crohn's, celiac disease, and chronic gastritis can impair absorption in the digestive tract.
Patients with Pernicious Anemia: An autoimmune condition where the body attacks cells producing intrinsic factor, crucial for B12 absorption.
Post-Bariatric Surgery Patients: Procedures altering the stomach or intestines significantly reduce absorption capacity.
Medication Users: Some medications, including metformin and PPIs, can interfere with B12 absorption with long-term use.
Chronic Alcohol Users: Excessive alcohol can damage the digestive system and impair nutrient absorption.

Unveiling the Symptoms of B12 Deficiency

Symptoms of B12 deficiency can take years to manifest due to the body's storage capacity and are often non-specific. Early detection is vital as chronic, low-grade deficiency can cause irreversible nerve damage.

Common Symptoms of Vitamin B12 Deficiency:

Physical: Fatigue, weakness, pale skin, sore tongue, and loss of appetite.
Neurological: Numbness or tingling in extremities, balance problems, and vision issues.
Psychological: Memory problems, cognitive decline, depression, and irritability.

Diagnosing and Treating B12 Deficiency

Diagnosis involves blood tests to measure B12 levels. More sensitive tests like methylmalonic acid (MMA) and holotranscobalamin (holoTC) can help identify functional deficiencies.

Treatment Comparison: Oral vs. Injections


Feature	Oral Supplementation	Intramuscular Injections	Considerations
Efficacy	Effective for most individuals, especially those with dietary deficiencies or mild malabsorption.	Most effective for severe deficiency, pernicious anemia, or significant malabsorption issues.	Effectiveness depends heavily on the cause of the deficiency.
Convenience	Easy to take at home, convenient, and non-invasive.	Requires regular visits to a clinic or self-injection training.	Oral options are preferable for many patients if absorption is sufficient.
Absorption Mechanism	Relies on passive diffusion in the gut, which is less efficient but bypasses the need for intrinsic factor.	Administered directly into the muscle, bypassing the digestive system entirely.	Determines suitability for different causes of deficiency.
Cost	Generally more affordable and cost-effective for long-term use.	Can be more expensive due to administration costs and the medication itself.	Costs vary by location and insurance coverage.

Conclusion: Awareness is Key

Vitamin B12 deficiency is a common and often undetected issue, with prevalence varying significantly by age and lifestyle. It impacts not just vegans and vegetarians, but also older adults and individuals with compromised gut health. The slow onset and non-specific nature of symptoms can lead to delayed diagnosis and potentially permanent nerve damage. Increased awareness of risk factors, regular monitoring for vulnerable individuals, and appropriate treatment through supplementation or injections are crucial for maintaining optimal health. Understanding dietary sources and consulting a healthcare provider are vital steps, especially for those at high risk. The National Institutes of Health (NIH) is a valuable resource for detailed information on nutrient functions: ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/.

Frequently Asked Questions

Older adults, individuals with certain gastrointestinal disorders (like Crohn's or celiac disease), those who have undergone bariatric surgery, vegans and vegetarians, and people taking specific medications like metformin and acid-suppressing drugs are at the highest risk.

Yes, if left untreated for a long period, severe B12 deficiency can lead to irreversible nerve damage, cognitive impairment, and other neurological issues.

Deficiency refers to a severely low level of vitamin B12, while insufficiency is a more common, marginal status. Insufficiency can still cause problems and may progress to full deficiency if unaddressed.

For severe deficiency or malabsorption issues (like pernicious anemia), injections are often necessary. However, for many, high-dose oral supplements are equally effective at correcting levels and are more convenient.

Early symptoms can be non-specific and include fatigue, weakness, lethargy, a sore tongue, and pins and needles sensations in the hands or feet.

No. While diet is a factor, especially for vegans and vegetarians, malabsorption issues in the gut are the most common cause of deficiency, affecting individuals with seemingly adequate B12 intake.

Diagnosis is based on blood tests, including measuring serum B12 levels. In some cases, more sensitive markers like methylmalonic acid (MMA) and homocysteine levels are checked to confirm a functional deficiency.