What anemia does B6 deficiency cause?

January 6, 2026 •

3 min read

A vitamin B6 deficiency can lead to a specific type of blood disorder, most commonly sideroblastic anemia, where the body fails to properly synthesize hemoglobin. This occurs because vitamin B6 is a crucial coenzyme in the initial and rate-limiting step of heme synthesis, a core component of hemoglobin.

Quick Summary

Vitamin B6 deficiency can result in sideroblastic anemia, a condition where the body cannot properly incorporate iron into red blood cells, leading to microcytic and hypochromic cells.

Key Points

Sideroblastic Anemia: B6 deficiency primarily causes sideroblastic anemia, where red blood cell precursors are unable to incorporate iron into hemoglobin.
Heme Synthesis Impairment: Vitamin B6 is a key coenzyme for the first step of heme production; a deficiency blocks this process.
Microcytic and Hypochromic: The resulting red blood cells are often smaller and paler than normal, a condition known as microcytic and hypochromic anemia.
Secondary Causes: Deficiency is frequently secondary to conditions like alcoholism, kidney disease, malabsorption disorders, or use of certain medications.
Symptom Recognition: Common signs include fatigue, shortness of breath, and neurological issues such as confusion or peripheral neuropathy.
Effective Treatment: The anemia is typically treatable with oral vitamin B6 supplementation once the underlying cause is addressed.

Sideroblastic Anemia: The Primary Link

Vitamin B6, also known as pyridoxine, plays a critical role in the human body, particularly in the production of red blood cells. Its active form acts as a coenzyme in the synthesis of heme, a vital component of hemoglobin. Insufficient vitamin B6 disrupts this process, preventing iron from being incorporated into hemoglobin. This leads to iron buildup in the mitochondria of red blood cell precursors in the bone marrow, forming 'ringed sideroblasts'. The resulting condition is called sideroblastic anemia.

The Different Faces of B6-Related Anemia

While sideroblastic anemia is the most direct result of B6 deficiency, the appearance of red blood cells can vary. Often, it presents as microcytic and hypochromic anemia, with red blood cells being smaller and paler than usual due to low hemoglobin. However, some individuals might have normocytic anemia or a mix of cell sizes. This variability, along with potential co-existing deficiencies of other B-vitamins, can complicate diagnosis.

Causes of Vitamin B6 Deficiency

Dietary B6 deficiency is uncommon in developed nations because the vitamin is widely available in many foods. However, secondary deficiency is more frequent and can be caused by various factors:

Alcohol Use Disorder: Excessive alcohol impairs B6 metabolism.
Kidney Disease: Impaired kidney function, especially with dialysis, increases the risk of B6 deficiency.
Malabsorption Syndromes: Conditions like celiac disease and inflammatory bowel diseases hinder nutrient absorption.
Medications: Drugs such as isoniazid can interfere with B6 metabolism.
Genetic Factors: Rare inherited disorders can affect B6 utilization, requiring high-dose supplementation.

Key Symptoms to Watch For

Symptoms of B6 deficiency can overlap with general anemia and include fatigue, weakness, shortness of breath, headaches, and heart palpitations. Other potential signs are skin conditions like seborrheic dermatitis, neurological symptoms such as confusion, depression, or peripheral neuropathy, and in infants, irritability and seizures.

Diagnosis and Treatment

Diagnosing anemia due to B6 deficiency involves a clinical assessment and blood tests showing microcytic or hypochromic red blood cells. Measuring serum B6 levels can confirm the deficiency. In suspected sideroblastic anemia, a bone marrow biopsy may be used to identify ringed sideroblasts, though it's not always required.

Treatment focuses on addressing the root cause and supplementing with vitamin B6 (pyridoxine). For dietary deficiency, oral supplements are usually effective. Patients on B6-interfering medications, like isoniazid, often receive preventative supplementation. Higher doses might be needed for severe deficiencies or genetic conditions under medical guidance.

Dietary Sources of Vitamin B6

A balanced diet helps prevent B6 deficiency. Good sources include:

Animal Products: Fish (tuna, salmon), beef liver, chicken, turkey.
Plant-Based Foods: Chickpeas, potatoes, bananas, fortified cereals.
Other Sources: Certain nuts, non-citrus fruits, legumes.

B6 Deficiency Anemia vs. Iron Deficiency Anemia

Both can cause microcytic, hypochromic anemia, but they have different causes and lab results.


Feature	B6 Deficiency Sideroblastic Anemia	Iron Deficiency Anemia
Underlying Cause	Impaired heme synthesis due to B6 lack	Insufficient iron for hemoglobin
Bone Marrow Findings	Ringed sideroblasts	No ringed sideroblasts; normal iron handling
Iron Stores (Serum Ferritin)	Usually normal to high	Low
Total Iron-Binding Capacity (TIBC)	Often normal or low	High
Primary Treatment	B6 supplementation	Iron supplementation

Conclusion

Vitamin B6 deficiency primarily leads to sideroblastic anemia, characterized by faulty heme production and the presence of ringed sideroblasts in bone marrow. This often manifests as microcytic and hypochromic anemia, though other red cell sizes are possible. Causes are typically secondary, such as alcoholism, kidney disease, or medications, rather than solely dietary. Timely diagnosis and treatment, usually involving B6 supplementation, are crucial for resolving the anemia and avoiding complications. Always consult a healthcare provider for diagnosis and management.

Frequently Asked Questions

Sideroblastic anemia is a type of blood disorder where the body produces enough iron but is unable to incorporate it into hemoglobin to form healthy red blood cells. This leads to a build-up of iron in the red blood cell precursors within the bone marrow, creating ringed sideroblasts.

Vitamin B6 is a crucial coenzyme for the enzyme δ-aminolevulinic acid synthase (ALAS), which catalyzes the first step of heme synthesis. Without enough B6, this process is inhibited, causing a defect in hemoglobin formation and leading to the accumulation of iron in developing red blood cells.

While B6 deficiency often leads to microcytic and hypochromic anemia, where red blood cells are small and pale, it is not always the case. Some individuals may present with normocytic anemia, or a mixture of different red cell sizes.

Common causes of B6 deficiency include chronic alcohol use, end-stage renal disease (especially with dialysis), malabsorption syndromes like Crohn's and celiac disease, and certain medications such as isoniazid. Dietary deficiency is rare in those with a balanced diet.

Symptoms include fatigue, shortness of breath, headache, heart palpitations, and pale skin. In more severe cases, it can cause neurological problems like confusion or peripheral neuropathy, skin rashes, and a weakened immune system.

Treatment involves addressing the underlying cause of the deficiency and providing vitamin B6 supplementation, typically with pyridoxine. The specific dosage and duration depend on the severity and cause of the deficiency.

Excellent food sources of vitamin B6 include fish (tuna, salmon), beef liver, poultry, chickpeas, potatoes, and bananas. Many breakfast cereals are also fortified with B6.

Yes, some medications can interfere with B6 metabolism and lead to a deficiency. A prominent example is the antibiotic isoniazid, used to treat tuberculosis, which is why patients taking it are often given B6 supplements.