Vitamin B6 (Pyridoxal-5-Phosphate)
Vitamin B6 is measured through pyridoxal-5-phosphate (PLP), its active form in the body. B6 helps your body process proteins, make neurotransmitters, and support red blood cell and immune function.
B6 is involved in a wide range of chemical reactions, so adequate levels support your nervous system, metabolism, and blood. PLP is the preferred marker because it reflects the usable, active form. Levels can be affected by diet, certain medications, alcohol use, and some medical conditions.
A high B6 level most often reflects supplementation. Although B6 is water-soluble, very high intakes from supplements over long periods have been linked to nerve symptoms such as tingling, so a high result is worth discussing before continuing high doses. Getting B6 from food alone does not carry this concern.
A low B6 suggests your intake or metabolism may not be meeting your needs, which can affect nerves, mood, and blood over time. It can also contribute to elevated homocysteine.
Most labs list a normal range for active B6, and both low and very high values may warrant a closer look at your diet and supplements. A clinician can help you interpret your result.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.