Vitamin B supplements, especially those containing riboflavin (vitamin B2), often cause bright yellow or neon colored urine. This happens because excess riboflavin is water soluble and is excreted through urine when the body has Why Is My Urine Yellow After Taking Vitamin B? Vitamin B supplements, especially those containing riboflavin (vitamin B2), often cause bright yellow or neon colored urine. This happens because excess riboflavin is water soluble and is excreted through urine when the body has Multifunctional Eu doped carbon dots nanoprobe for highly sensitive and selective determination of glutathione in biological fluid and cell imaging ScienceDirect Neon yellow pee after taking supplements EXPLAINED YouTube