From the FDA Drug Label
CLINICAL PHARMACOLOGY Natural substances that have vitamin B6 activity are pyridoxine in plants and pyridoxal or pyridoxamine in animals. All 3 are converted to pyridoxal phosphate by the enzyme pyridoxal kinase. The physiologically active forms of vitamin B6 are pyridoxal phosphate (codecarboxylase) and pyridoxamine phosphate The FDA drug label does not answer the question.
From the Research
The optimal serum vitamin B6 level is between 20-80 ng/mL, and levels above 100 ng/mL may indicate oversupplementation and potentially cause peripheral neuropathy, as evidenced by a study published in 2008 1. To determine the optimal serum vitamin B6 level, it's essential to consider the potential risks and benefits associated with different levels of vitamin B6.
- A study published in 2022 found that higher serum PLP concentrations (> 63.6 nmol/L) were associated with a decrease in all-cause mortality in patients with type 2 diabetes mellitus 2.
- However, another study published in 2008 found that elevated B6 levels can cause peripheral neuropathy, with symptoms such as numbness, burning pain, and tingling 1.
- A more recent study published in 2025 found that vitamin B6 deficiency was not significantly correlated with anemia in children on regular hemodialysis, with a median serum vitamin B6 concentration of 28.2 ng/ml 3.
- Additionally, a study published in 2015 highlighted the antioxidant properties of vitamin B6 and its role in regulating cellular calcium transport, which can help control hypertension 4.
- Another study published in 2012 discussed the importance of pyridoxal 5'-phosphate (PLP) in various metabolic pathways, including neurotransmitter synthesis and degradation, and the potential consequences of reduced PLP availability, such as severe neurological disorders 5.
Considering the potential risks and benefits, maintaining a serum vitamin B6 level between 20-80 ng/mL is crucial for proper physiological function, and excessive levels above 100 ng/mL should be avoided.
- For most healthy adults, supplementation may be warranted if testing reveals levels below 20 ng/mL.
- Typical supplementation for mild deficiency involves taking 25-100 mg of pyridoxine daily for several weeks, followed by maintenance dosing of 2-10 mg daily.
- For severe deficiency, higher doses of 50-200 mg daily may be prescribed initially.
- Regular monitoring is recommended for those on long-term supplementation to prevent oversupplementation and potential peripheral neuropathy.