How Common Is B12 Deficiency in the US?

December 29, 2025 •

5 min read

While severe clinical vitamin B12 deficiency is relatively rare in the United States, milder, subclinical deficiency and insufficiency are far more common, especially among certain populations. This article explores the prevalence of B12 deficiency in the U.S. and identifies key demographic and lifestyle factors contributing to it.

Quick Summary

This guide details the prevalence of B12 deficiency in the US, highlighting statistics and at-risk groups like older adults, vegans, and those with certain medical conditions. It also discusses causes, symptoms, and potential treatments for addressing insufficient B12 levels.

Key Points

Prevalence Increases with Age: While clinical B12 deficiency is uncommon in young and middle-aged adults, its prevalence rises significantly to nearly 20% in those over 60 in the US.
Risk Groups Beyond Age: Besides older adults, individuals following strict vegan diets, those with gastrointestinal disorders (like Crohn's disease or pernicious anemia), and patients on certain long-term medications (such as metformin and acid-blockers) are at increased risk.
Absorption vs. Intake: Most B12 deficiencies in the US are caused by malabsorption issues rather than inadequate dietary intake alone. Factors like reduced stomach acid or surgical changes can prevent the body from properly absorbing the vitamin from food.
Subtle vs. Severe Symptoms: The signs of B12 deficiency can range from mild fatigue and weakness to more serious neurological issues like tingling, memory loss, and balance problems. Early symptoms are often non-specific, leading to delayed diagnosis.
Neurological Damage Can Be Permanent: Untreated, severe B12 deficiency can lead to irreversible neurological damage. However, early diagnosis and treatment can reverse many symptoms.
Treatments Vary: Depending on the cause and severity, B12 deficiency is treated with oral supplements or injections. Injections are often necessary for cases of severe malabsorption.

Prevalence of Vitamin B12 Deficiency by Age

According to research based on data from the National Health and Nutrition Examination Survey (NHANES), the prevalence of vitamin B12 deficiency varies significantly across different age groups in the US. While deficiency is less common in younger adults, it increases notably with age due to various physiological changes.

Adults under 60: Some estimates suggest that approximately 6% of people under the age of 60 have a vitamin B12 deficiency.
Older Adults (60+): The prevalence rises significantly in older adults, with estimates suggesting that nearly 20% of those over 60 years old are deficient. Other data indicates that functional deficiency, or insufficient levels, may affect over 20% of this population.

This age-related increase is often linked to a decrease in stomach acid production, which is necessary for the absorption of food-bound B12. This can make dietary sources of the vitamin less effective for older individuals.

Groups at Increased Risk of B12 Deficiency

Beyond age, several other factors predispose individuals to a higher risk of developing a B12 deficiency. Understanding these risk groups is essential for proactive health management and monitoring.

Dietary Restrictions

Since vitamin B12 is primarily found in animal products, dietary restrictions pose a significant risk factor.

Vegans and Vegetarians: Individuals who consume no animal products (vegans) or limited animal products (vegetarians) are at a high risk of deficiency if they don't supplement their diet with fortified foods or B12 supplements. Their B12 stores can be depleted over several years following the adoption of a restricted diet.
Infants of Vegan Mothers: Exclusively breastfed infants of mothers with a vegan diet can develop severe B12 deficiency due to the low vitamin content in breast milk.

Gastrointestinal Conditions and Surgeries

Proper B12 absorption relies on a healthy and functioning digestive system. Conditions that interfere with this process dramatically increase the risk of deficiency.

Pernicious Anemia: This autoimmune condition prevents the production of intrinsic factor, a protein essential for B12 absorption. It is the most common cause of clinically evident B12 deficiency worldwide.
Atrophic Gastritis: Common in older adults, this chronic inflammation of the stomach lining reduces stomach acid and intrinsic factor production, hindering B12 release from food.
Gastric Surgery: Procedures like gastric bypass surgery can remove or alter parts of the stomach and small intestine, significantly impairing B12 absorption.
Crohn's and Celiac Disease: These inflammatory diseases affect the small intestine, where B12 is absorbed, thereby causing malabsorption.

Medications

Long-term use of certain medications can also deplete B12 levels over time by affecting stomach acid or nutrient absorption.

Acid-Suppressing Drugs: Proton pump inhibitors (PPIs) and H2 blockers used to treat GERD and ulcers reduce stomach acid needed to release B12 from food.
Metformin: This common diabetes medication has been shown to significantly reduce B12 absorption and lower serum B12 concentrations.

The Spectrum of B12 Deficiency

It's important to recognize that a B12 deficiency exists on a spectrum, with symptoms and severity varying accordingly.


Deficiency Stage	Clinical Characteristics	Potential Symptoms
Stage I (Low Serum Level)	Initial depletion, but cellular stores may be sufficient. Blood B12 is low.	Often asymptomatic.
Stage II (Low Cell Store)	The body's cellular B12 reserves become depleted, indicated by low B12 levels in cells.	Subtle neurological or psychological symptoms may begin.
Stage III (Biochemical Deficiency)	Metabolite levels like methylmalonic acid (MMA) and homocysteine rise, showing metabolic impairment.	Clearer neurological and psychological issues, including confusion, memory problems, and irritability.
Stage IV (Clinically Evident)	Red blood cells become abnormally large (macrocytic anemia). Hematological and neurological symptoms are pronounced.	Severe fatigue, weakness, numbness, tingling, cognitive decline, and balance issues.

Conclusion: A Common But Often Overlooked Problem

While serious B12 deficiency is not extremely widespread in the general US population, the number of individuals with insufficient or marginal levels is much higher, especially among older adults, vegans, and those with gastrointestinal issues. Because early symptoms can be subtle and easily mistaken for other conditions, B12 deficiency is often overlooked. Regular screening for at-risk individuals, coupled with targeted dietary changes, supplementation, or injections, is critical for preventing potentially irreversible neurological damage. Given its role in nerve function and DNA synthesis, addressing B12 levels is a crucial step for overall health.

For more in-depth information, the National Institutes of Health provides a comprehensive fact sheet on Vitamin B12: https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/.

How is a B12 deficiency diagnosed?

A B12 deficiency is typically diagnosed through a blood test that measures serum vitamin B12 levels, along with other markers like methylmalonic acid (MMA) and homocysteine. A complete blood count (CBC) may also reveal macrocytic anemia, which is characterized by abnormally large red blood cells. For individuals with borderline B12 levels, MMA and homocysteine tests can help confirm a functional deficiency.

Can B12 deficiency be permanent?

Some neurological problems caused by a severe, untreated B12 deficiency can become permanent. This is because the vitamin is essential for maintaining the myelin sheath that protects nerves. However, if caught early, many symptoms can be resolved with treatment. Treatment is particularly effective for reversing symptoms related to anemia, but mental function and nerve damage in older individuals may not fully improve.

What are the most common symptoms of B12 deficiency?

The most common symptoms are often non-specific and include:

Fatigue and weakness: Due to megaloblastic anemia, which impairs oxygen transport.
Neurological signs: Numbness, tingling, or a 'pins and needles' sensation in the hands and feet.
Cognitive issues: Confusion, forgetfulness, and mood changes.
Gastrointestinal symptoms: Loss of appetite, weight loss, constipation, or diarrhea.

Can a vegetarian or vegan diet lead to B12 deficiency?

Yes, since natural food sources of vitamin B12 are almost exclusively animal-based, vegans and vegetarians are at a higher risk of deficiency. They must consume fortified foods (like cereals or nutritional yeast) or take regular B12 supplements to maintain adequate levels.

How is B12 deficiency treated?

Treatment depends on the severity and underlying cause. For milder cases, high-dose oral supplements may be sufficient. In cases of malabsorption (like pernicious anemia) or severe deficiency with neurological symptoms, vitamin B12 injections are typically required. These injections may be administered initially and then less frequently for maintenance.

What medications can interfere with B12 absorption?

Several common medications can interfere with B12 absorption. These include:

Metformin: A medication for diabetes.
Proton pump inhibitors (PPIs) and H2-blockers: Medications for acid reflux and ulcers.
Long-term antibiotic use: Can alter gut bacteria.

Why are older adults at a higher risk for B12 deficiency?

Older adults face a higher risk primarily due to impaired absorption. As people age, stomach acid production can decrease (a condition called atrophic gastritis), which makes it harder to release vitamin B12 from the proteins in food. This issue doesn't affect the absorption of synthetic B12 in supplements as much, which is why supplementation is often recommended.

Frequently Asked Questions

While estimates vary depending on the diagnostic criteria, some data indicates that around 6% of the US population under age 60 has a B12 deficiency, while nearly 20% of adults over 60 are affected. Insufficiency or marginal status can be even more widespread.

The highest-risk groups include older adults, people with pernicious anemia or other gastrointestinal disorders (like Crohn's and celiac disease), individuals who have had gastric surgery, and those following strict vegan or vegetarian diets.

Early signs can be subtle and include fatigue, weakness, headaches, and a sore tongue. Because symptoms can be vague, the condition is often missed or misdiagnosed.

If left untreated, a B12 deficiency can cause serious, long-term complications including severe anemia, nerve damage (neuropathy), and irreversible neurological damage, which can lead to cognitive decline, memory loss, and problems with balance and vision.

Yes, B12 deficiency can cause nerve damage because the vitamin is crucial for the maintenance of the myelin sheath, which insulates and protects nerves. Severe deficiency can lead to a condition called subacute combined degeneration of the spinal cord.

Medications such as metformin, used for diabetes, and proton pump inhibitors (PPIs), used for acid reflux, can interfere with vitamin B12 absorption. Long-term use can significantly reduce serum B12 concentrations, necessitating regular monitoring.

Yes, if you follow a vegan or vegetarian diet, it is highly recommended to take a B12 supplement or consume fortified foods regularly. Natural B12 is almost exclusively found in animal products, and your body's stores can be depleted over several years.