What is the Cause of Vitamin B6 Deficiency?

October 16, 2025 •

3 min read

While isolated dietary insufficiency is relatively rare in developed countries, analyses of health data from 2003-2004 showed that up to 24% of U.S. adults not taking supplements had low plasma B6 concentrations, indicating a more complex issue. It is this underlying complexity, rather than just diet, that often explains what is the cause of vitamin B6 deficiency.

Quick Summary

Low vitamin B6 status is most often a secondary issue stemming from medical conditions like kidney disease or autoimmune disorders, or due to certain medications, and chronic alcohol use. Inadequate diet, while possible, is less common.

Key Points

Chronic Illness: Conditions such as kidney disease, celiac disease, inflammatory bowel disease, and autoimmune disorders like rheumatoid arthritis are major causes of vitamin B6 deficiency.
Medication Interference: Certain drugs, including the tuberculosis antibiotic isoniazid and some anticonvulsants, disrupt B6 metabolism and can lead to depletion.
Alcohol Dependence: Chronic and excessive alcohol consumption produces acetaldehyde, which interferes with the body's utilization of vitamin B6, resulting in deficiency.
Malabsorption Issues: Disorders that compromise nutrient absorption in the gut, including gastrointestinal surgery, prevent the body from obtaining sufficient B6 from food.
Underlying, Not Just Diet: While dietary inadequacy is a potential factor, most cases of vitamin B6 deficiency in developed countries are secondary to other health issues, not just poor eating habits.

Beyond the Diet: Understanding the Causes of Vitamin B6 Deficiency

Although vitamin B6 is readily available in a wide variety of foods, a deficiency can still occur due to multiple factors that interfere with its absorption and utilization in the body. Understanding these secondary causes is crucial for proper diagnosis and management. The most common drivers of low vitamin B6 levels are related to chronic medical conditions, certain prescription drugs, and substance abuse, rather than simply a poor diet.

Chronic Medical Conditions and Impaired Absorption

Several health issues can significantly impact the body's ability to maintain adequate vitamin B6 levels. These conditions can either hinder the vitamin's absorption in the digestive tract or interfere with its metabolism, preventing it from being converted into its active form, pyridoxal 5-phosphate (PLP).

Malabsorptive syndromes: Conditions that affect nutrient absorption in the small intestine are a prime cause. This includes inflammatory bowel diseases (IBD) such as Crohn's disease and ulcerative colitis, as well as celiac disease. Surgical procedures like bariatric surgery can also lead to malabsorption issues.
Kidney diseases: Patients with impaired renal function, including those with end-stage renal disease or those on dialysis, frequently have low plasma vitamin B6 concentrations. The increased metabolic clearance of PLP in these individuals contributes to their deficient status.
Autoimmune disorders: Conditions characterized by chronic inflammation, such as rheumatoid arthritis, can increase the body's rate of vitamin B6 catabolism. This leads to a higher demand for the vitamin and can result in deficiency.
Liver dysfunction: Liver disease, including cirrhosis, can reduce the liver's ability to metabolize and store vitamin B6 effectively. Excessive alcohol intake also harms the liver and impairs B6 status.

Medications That Deplete Vitamin B6

A number of common prescription drugs are known to interfere with vitamin B6 metabolism, leading to a deficiency over time. Patients on long-term treatment with these medications often require intervention to prevent adverse effects.

Isoniazid (INH): This antibiotic, used to treat and prevent tuberculosis, is a classic cause of B6 deficiency. It forms a complex with pyridoxine, increasing its excretion from the body.
Anticonvulsant medications: Several antiepileptic drugs, including phenytoin and carbamazepine, can accelerate the breakdown of vitamin B6, lowering its plasma concentrations.
Cycloserine: This broad-spectrum antibiotic also used for tuberculosis can increase the urinary excretion of pyridoxine, heightening the risk of neurotoxicity.
Hydralazine: This medication for high blood pressure can cause vitamin B6 depletion.
D-penicillamine: Used for conditions like rheumatoid arthritis and Wilson disease, it can also lead to reduced B6 levels.

Lifestyle and Genetic Factors

Certain lifestyle choices and rare genetic factors can also contribute to low vitamin B6 levels.

Chronic Alcoholism: Alcohol dependence is a significant risk factor, as alcohol is broken down into acetaldehyde, which decreases the amount of active vitamin B6 in the body.
Malnutrition: While rare in most developed nations, severe protein-energy malnutrition is a direct cause of vitamin B6 deficiency.
Excessive Processing of Food: Extensive processing of foods can deplete them of their natural vitamin B6 content, potentially contributing to inadequate intake, though this is less common than other factors.
Genetic Disorders: Inborn errors of metabolism, though extremely rare, can affect the body's ability to process and utilize pyridoxine.

Comparing Causes: Dietary vs. Secondary Deficiency


Feature	Primary (Dietary) Deficiency	Secondary Deficiency
Commonality	Rare in developed countries	More common, especially in at-risk populations
Underlying Problem	Insufficient intake of B6-rich foods	Impaired absorption, metabolism, or increased excretion due to another health issue
Associated Factors	Severe malnutrition, poor and restrictive diets	Chronic disease (renal, autoimmune), medication use, alcoholism
Dietary Solution	Improved diet with B6-rich foods (meat, fish, bananas, chickpeas)	Dietary changes may help but are often insufficient on their own
Treatment Focus	Address nutritional gaps through diet	Treat the underlying condition and address B6 levels

Conclusion

In conclusion, pinpointing the specific cause of vitamin B6 deficiency requires considering more than just dietary intake. While a poor diet can contribute, the majority of cases in modern society are linked to underlying health conditions such as kidney or autoimmune diseases, or the use of specific medications that interfere with B6 metabolism. Chronic alcoholism is another major factor that significantly impairs the body's vitamin B6 status. For those at risk, particularly due to medication, chronic illness, or advanced age, addressing the root cause and vitamin B6 status is the most effective approach to correcting the deficiency and preventing further health complications. For more information on vitamin B6, consult the National Institutes of Health Office of Dietary Supplements.

Frequently Asked Questions

No, while poor dietary intake can be a factor, it is often not the sole cause, particularly in developed countries. Deficiency is more frequently linked to underlying medical conditions, certain medications, and excessive alcohol consumption.

Several medications interfere with B6, including isoniazid (for tuberculosis), some anticonvulsants (like phenytoin and carbamazepine), hydralazine (for high blood pressure), and D-penicillamine.

Chronic alcohol consumption affects vitamin B6 status by producing acetaldehyde, which impairs the body's ability to convert B6 into its active form. This disrupts metabolic processes and can lead to deficiency.

Medical conditions linked to deficiency include kidney disease, autoimmune disorders (like rheumatoid arthritis), inflammatory bowel disease (Crohn's, ulcerative colitis), and celiac disease.

Yes, older age is considered a risk factor. As people age, several factors can contribute to lower vitamin levels, including potentially reduced intake or absorption, and chronic conditions that increase the need for B6.

Yes, pregnant and breastfeeding women have increased vitamin B6 requirements. This makes them more susceptible to deficiency, especially if their diet is inadequate or if they experience prolonged morning sickness.

Addressing vitamin B6 deficiency usually involves identifying and treating the underlying cause and considering ways to support adequate vitamin B6 levels.