Vitamin B6, Plasma

Vitamin B6 is an important nutrient your body needs for brain function, making red blood cells, and processing proteins from food. Your blood test measures how much active vitamin B6 is available in your body. Too little can cause symptoms like tingling in the hands and feet, skin problems, or low mood, while too much—usually from taking high-dose supplements—can also harm the nerves. Most people get enough B6 from a balanced diet, but certain medications, digestive conditions, or alcohol use can lower your levels. Talk with your healthcare provider before starting or changing any B6 supplements.

When elevated: Elevated vitamin B6 levels are most commonly associated with excessive supplementation rather than dietary intake alone. Chronically high plasma PLP concentrations, particularly from long-term high-dose pyridoxine supplementation, have been linked to sensory peripheral neuropathy (pyridoxine toxicity), which may be irreversible in severe cases. Elevated levels in the absence of supplementation may warrant investigation into underlying hepatic disease, as the liver is the primary site of PLP metabolism. When low: Low vitamin B6 status is associated with peripheral neuropathy, seborrheic dermatitis, glossitis, cheilosis, and microcytic hypochromic anemia due to impaired heme synthesis. Neuropsychiatric symptoms including irritability, confusion, and depression may occur, reflecting reduced neurotransmitter synthesis. Suboptimal B6 also impairs homocysteine metabolism via the transsulfuration pathway, contributing to hyperhomocysteinemia, which is an independent cardiovascular risk marker.

Vitamin B6 supports amino acid metabolism and muscle protein synthesis, critical during high training volume and recovery phases. It's also essential for neurotransmitter production (serotonin, dopamine) and energy metabolism, which influence mood, stress resilience, and exercise performance—making adequate status relevant for athletes managing intense training and recovery demands.