Riboflavin (B2) is a bright yellow and fluorescent under UV light. B12 is red and aiui it takes a LOT of B12 to turn urine red. This happens because both are wa

Riboflavin (B2) is a bright yellow and fluorescent under UV light. B12 is red and aiui it takes a LOT of B12 to turn urine red. This happens because both are water-soluble.