Megavitamin-B6 syndrome

Megavitamin-B6 syndrome, also known as hypervitaminosis B6 or vitamin B6 toxicity, is a collection of symptoms that results from chronic supplementation or acute overdose of vitamin B6. Although vitamin B6 is water-soluble, it accumulates in muscle, plasma, liver, red blood cells and other protein-bound tissue with a half-life of roughly two to four weeks, allowing excess intake to build up. The hallmark effect is peripheral sensory neuropathy, with numbness, pins-and-needles sensations and burning in the limbs, along with unsteady gait, heightened sensitivity to stimuli and reduced vibration and position sense. The condition is generally, though not always, reversible once supplementation stops, with most cases resolving within six months, though symptoms can briefly worsen before they improve.