What Depletes Vitamin B12 From Your Body?: Causes, Symptoms, and Solutions

October 1, 2025 •

4 min read

Did you know that despite the body storing vitamin B12 for several years, various factors beyond diet can accelerate its depletion from your body? Understanding what depletes vitamin B12 from your body is crucial for maintaining proper neurological function and red blood cell production. This guide explores the common culprits behind B12 deficiency.

Quick Summary

Vitamin B12 depletion can result from malabsorption due to autoimmune conditions like pernicious anemia, gastrointestinal diseases, surgical procedures, certain medications, dietary limitations, and age-related factors.

Key Points

Dietary Source: Vitamin B12 is found almost exclusively in animal products, making vegans and vegetarians susceptible to deficiency without supplementation.
Absorption is Key: Even with adequate intake, conditions like pernicious anemia or gastric surgery can prevent the body from absorbing B12 effectively.
Medication Interference: Common drugs, including metformin for diabetes and PPIs for acid reflux, can reduce stomach acid, which is necessary for B12 absorption.
Neurological Impact: B12 depletion can cause serious neurological symptoms, such as numbness, fatigue, and memory loss, which may become permanent if left untreated.
Chronic Illnesses: Digestive disorders like Crohn's disease and celiac disease, along with chronic alcohol use, are major culprits behind malabsorption.
Age-Related Risk: Older adults are at a higher risk due to naturally declining stomach acid production, which impairs B12 release from food.

The Complexities of B12 Absorption and Depletion

Vitamin B12, or cobalamin, is a vital nutrient for nerve health, DNA synthesis, and red blood cell formation. Unlike many vitamins, it is not produced by the body and must be acquired through animal products or supplements. Even with sufficient intake, a complex digestive process must function correctly for the body to absorb it. First, stomach acid releases B12 from the food protein it's attached to. Then, the B12 binds with a protein called intrinsic factor, which is also made in the stomach. This complex then travels to the small intestine (ileum), where it can be absorbed into the bloodstream. A breakdown at any point in this process can lead to significant depletion over time.

Primary Causes of Vitamin B12 Depletion

Dietary Restrictions

For people who do not consume animal products, a primary cause of depletion is simply a lack of dietary intake. This is a significant concern for strict vegans and, to a lesser extent, vegetarians, as plant-based foods do not naturally contain vitamin B12. While fortified foods and supplements are available, inconsistent intake can lead to a deficiency over time, as the body's stored reserves are gradually used up.

Autoimmune Conditions

Pernicious anemia is a common autoimmune disease that specifically targets the cells in the stomach responsible for producing intrinsic factor. Without this vital protein, the body cannot absorb vitamin B12 from food, regardless of how much is consumed. This condition is more common in women around 60 years of age and people with other autoimmune diseases, like type 1 diabetes. Another related condition is autoimmune metaplastic atrophic gastritis, where the immune system attacks the stomach lining, leading to a loss of intrinsic factor.

Gastrointestinal Disorders and Surgery

Chronic conditions affecting the digestive system can impair B12 absorption. Disorders like Crohn's disease and celiac disease, which cause inflammation in the intestines, can damage the part of the small intestine where B12 is absorbed. Surgical procedures, such as gastrectomy (removal of part or all of the stomach) or gastric bypass surgery, can significantly reduce the body's ability to produce stomach acid and intrinsic factor. Furthermore, a bacterial overgrowth in the small intestine can cause bacteria to consume the vitamin before the body can absorb it.

Medications and Other Substances

Certain long-term medications can interfere with vitamin B12 absorption.

Medications that can deplete B12 include:

Metformin: Commonly used to treat type 2 diabetes, long-term use is associated with reduced B12 levels.
Proton Pump Inhibitors (PPIs) and H2 Blockers: Used to reduce stomach acid for conditions like acid reflux and ulcers. By reducing stomach acid, they impair the release of B12 from its food protein.
Nitrous Oxide: Also known as laughing gas, repeated recreational exposure can inactivate vitamin B12.
Excessive Alcohol: Chronic alcohol consumption can damage the stomach lining and impair nutrient absorption.

Age-Related Factors

As people age, particularly those over 65, the production of stomach acid tends to decrease, a condition known as atrophic gastritis. This reduced stomach acidity makes it harder for the body to separate vitamin B12 from food proteins, thus hindering absorption. However, older individuals with this condition can still absorb synthetic B12 from supplements or fortified foods.

Symptoms and Risk Factors

Symptoms of vitamin B12 depletion often develop slowly and can be easily overlooked, but they can be severe if left untreated. Common symptoms include fatigue, weakness, nerve damage (tingling, numbness), balance issues, cognitive changes (memory problems, confusion), and mood disturbances. The deficiency can also lead to megaloblastic anemia, which causes abnormally large red blood cells.

Treatment and Prevention Strategies

Treatment for B12 deficiency depends on the underlying cause. In cases of malabsorption, injections of hydroxocobalamin are often required, as they bypass the digestive system entirely. For dietary-related deficiencies or mild cases, high-dose oral supplements may be effective. Working with a healthcare provider is essential to determine the correct dosage and form of treatment.

Prevention involves addressing the specific risk factors. For vegans and vegetarians, consistent intake of fortified foods (like certain cereals and plant-based milks) or supplements is necessary. Individuals with gastrointestinal issues or those taking interfering medications should be monitored regularly by their doctor. Moderating alcohol intake is also a key preventative measure for all adults.

Comparison of B12 Depletion Causes


Cause	Mechanism of Depletion	Associated Conditions/Factors
Dietary Insufficiency	Lack of B12 intake from food sources	Vegan or vegetarian diet, poor overall diet
Autoimmune Issues	Immune system attacks intrinsic factor or stomach cells	Pernicious anemia, autoimmune gastritis, Type 1 diabetes
Gastric Surgery	Reduces intrinsic factor or stomach acid production	Gastric bypass, gastrectomy
Medications	Interference with stomach acid or absorption	Metformin, PPIs, H2 blockers
Alcohol Abuse	Damages stomach lining, impairs absorption	Chronic, heavy alcohol consumption
Gastrointestinal Disorders	Inflammation or damage to the small intestine	Crohn's disease, celiac disease, bacterial overgrowth

Conclusion

While a balanced diet is fundamental, understanding what depletes vitamin B12 from your body involves recognizing that simple nutritional intake isn't always the full story. Many medical conditions, surgical history, and even common medications can disrupt the body's ability to process and absorb this critical nutrient. Early recognition of symptoms and addressing underlying issues with professional guidance is key to preventing long-term and potentially irreversible complications. For those at risk, regular monitoring and supplementation are highly effective strategies for maintaining optimal B12 levels and overall health. National Institutes of Health (NIH) on Vitamin B12

Frequently Asked Questions

Yes, a vegan diet is a risk factor for B12 depletion because the vitamin is naturally found almost exclusively in animal products. Vegans and vegetarians must regularly consume fortified foods or take supplements to prevent a deficiency.

Long-term use of the diabetes medication metformin can interfere with the absorption of vitamin B12 in the small intestine, leading to gradual depletion of the body's stores.

Pernicious anemia is an autoimmune disease where the body's immune system attacks the stomach cells that produce intrinsic factor, a protein essential for B12 absorption. This prevents the body from absorbing B12 from food.

Yes, surgeries such as gastric bypass or removal of parts of the stomach or small intestine can significantly impair the body's ability to absorb vitamin B12, as these procedures alter the digestive process.

Older adults are at higher risk because they often have decreased stomach acid production (atrophic gastritis), which is necessary to release B12 from food. This makes absorption from food less efficient.

Initial symptoms can be subtle and include fatigue, weakness, and loss of appetite. As the deficiency worsens, neurological symptoms like tingling, numbness, balance problems, and cognitive issues may appear.

Prevention strategies include eating a balanced diet with B12-rich animal products, opting for fortified foods or supplements if on a plant-based diet, managing underlying digestive disorders, and monitoring levels if taking interfering medications.