What Causes a B6 Deficiency? Understanding the Risk Factors

October 14, 2025 •

3 min read

According to research from the National Health and Nutrition Examination Survey, plasma B6 levels are low in a notable percentage of the US population, especially among non-supplement users. Understanding what causes a B6 deficiency is the first step toward prevention and treatment.

Quick Summary

A B6 deficiency can stem from inadequate dietary intake, medical conditions that impair absorption, chronic alcohol use, or medications that interfere with B6 metabolism. Certain populations are at increased risk due to specific health issues or life stages.

Key Points

Inadequate Diet: Consuming a diet poor in B6-rich foods, especially processed items or relying on less bioavailable plant sources, is a direct cause.
Malabsorption: Gastrointestinal disorders like Celiac and Crohn's disease compromise the body's ability to absorb vital nutrients, including vitamin B6.
Chronic Alcoholism: Alcohol interferes with the metabolism of vitamin B6, leading to accelerated breakdown and significantly low levels.
Kidney Disease: Patients with renal impairment, particularly those on hemodialysis, experience increased loss and metabolic clearance of vitamin B6.
Medications: Certain drugs, including isoniazid, some anticonvulsants, and corticosteroids, are known to interfere with or deplete B6.
Autoimmune Disorders: Inflammatory conditions like rheumatoid arthritis increase the body's demand for and catabolism of vitamin B6.
Increased Demands: Life stages such as pregnancy increase B6 requirements, potentially leading to a deficiency if dietary intake is insufficient.

The Primary Causes of Vitamin B6 Deficiency

While a direct B6 deficiency from diet alone is relatively uncommon in developed countries, it can still occur, and several other factors contribute significantly to low pyridoxine levels. These causes can be broadly categorized into insufficient intake, issues with absorption or metabolism, and increased bodily demands.

Insufficient Dietary Intake

The most straightforward cause of a B6 deficiency is not consuming enough foods rich in this vitamin. This can be a concern for several reasons:

Poor Diet: Relying heavily on processed and nutrient-poor foods can lead to inadequate vitamin intake, as extensive processing can remove B6.
Vegetarian and Vegan Diets: While B6 is found in plant foods, the form found in meats and animal products (e.g., poultry, fish, organ meats) is more easily absorbed by the body. Individuals on exclusively plant-based diets may need to be mindful of their B6 intake or consider supplementation.
Protein-Energy Malnutrition: Severe malnutrition, particularly a deficiency in both protein and calories, is a known cause of vitamin B6 inadequacy.

Malabsorption Disorders

Certain medical conditions can interfere with the small intestine's ability to absorb nutrients, leading to a deficiency even with a proper diet. These include:

Celiac Disease: An autoimmune disorder where consuming gluten damages the small intestine, impairing nutrient absorption.
Inflammatory Bowel Diseases (IBD): Conditions such as Crohn's disease and ulcerative colitis cause chronic inflammation of the digestive tract, which can decrease the body's ability to absorb vitamins.
Bariatric Surgery: Surgical procedures that alter the digestive system, such as bariatric surgery, can lead to malabsorption and increased nutritional needs.

Chronic Alcohol Use

Chronic alcohol dependence is a significant risk factor for B6 deficiency. Alcohol metabolism produces acetaldehyde, which interferes with the body's ability to create the active form of vitamin B6, pyridoxal 5-phosphate (PLP). This accelerates the breakdown of B6 and can lead to very low plasma concentrations.

Kidney Disease and Hemodialysis

Individuals with impaired renal function, especially those undergoing hemodialysis, frequently have low B6 levels. This is due to the increased metabolic clearance of PLP, the active form of B6, from the body.

Medications That Interfere with B6 Metabolism

Several medications can deplete the body's B6 stores or interfere with its metabolism. These include those for tuberculosis (like isoniazid), some anticonvulsants (like phenytoin), and certain agents used for rheumatoid arthritis (like penicillamine).

Autoimmune and Inflammatory Disorders

Autoimmune disorders like rheumatoid arthritis and inflammatory conditions can cause increased catabolism of B6, leading to lower concentrations of the vitamin. This inflammatory response creates a higher demand for B6, which may not be met through standard dietary intake.

Comparison of Major B6 Deficiency Causes


Cause	Mechanism	At-Risk Groups	Key Contributing Factors
Poor Dietary Intake	Insufficient intake of B6-rich foods	Vegans, vegetarians, those on highly processed diets, malnourished individuals	Food processing, food insecurity, unbalanced diet
Malabsorption	Conditions hinder nutrient absorption in the gut	Those with Celiac disease, Crohn's, or post-bariatric surgery	Intestinal inflammation and damage
Chronic Alcoholism	Alcohol interferes with B6 metabolism	Individuals with long-term alcohol dependence	Acetaldehyde, a byproduct of alcohol breakdown
Kidney Disease	Increased metabolic clearance of B6	Patients with chronic renal failure and on dialysis	Loss of PLP, the active form of B6
Medications	Drugs that interfere with B6 enzymes or increase excretion	Individuals on isoniazid, anticonvulsants, or penicillamine	Specific drug interactions and their effect on B6 enzymes

Conclusion: Navigating the Complexities of B6 Deficiency

While frank vitamin B6 deficiency is not widespread among the general healthy population, marginal deficiency is a legitimate concern, especially for those with specific risk factors. The causes are varied and can be interconnected, involving dietary, medical, and lifestyle factors. It is clear that relying solely on a basic diet may not be enough for everyone, particularly those with underlying conditions or medication use. Regular monitoring and, in many cases, targeted supplementation under medical guidance are necessary for at-risk individuals. Addressing the root cause, whether it is dietary habits, a chronic illness, or a medication's side effect, is crucial for preventing the potentially serious symptoms associated with a B6 deficiency. For more information on vitamin B6, consult the National Institutes of Health's professional fact sheet on the topic.

Frequently Asked Questions

The most common causes of B6 deficiency are secondary to other factors rather than diet alone, including conditions causing malabsorption, chronic alcohol use, certain medications, and kidney disease.

Yes, chronic alcohol consumption is a major cause of B6 deficiency. Alcohol produces acetaldehyde, which disrupts the body's ability to activate and utilize vitamin B6.

Yes, malabsorption syndromes such as celiac disease, Crohn's disease, and ulcerative colitis can prevent the small intestine from properly absorbing vitamin B6 from food, resulting in a deficiency.

Yes, several medications are known to interfere with B6 metabolism or increase its excretion. Examples include isoniazid, certain anticonvulsants (like phenytoin), and penicillamine.

Individuals with impaired renal function, especially those on dialysis, can develop B6 deficiency due to the increased metabolic clearance of the active form of the vitamin during treatment.

While uncommon in developed nations, a diet consistently lacking B6-rich foods, or a diet high in processed foods (which may have less B6), can lead to a deficiency. Vegans and vegetarians may also need to monitor their intake carefully.

Yes, an inadequate B6 status is often associated with low concentrations of other B-complex vitamins, such as vitamin B12 and folic acid.

Yes, autoimmune disorders like rheumatoid arthritis can lead to an increased catabolism of vitamin B6, which lowers its concentrations in the body and often necessitates supplementation.