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 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 What Is Glutathione? Purifi IV Tylenol, Autism, And The Glutathione Connection OC Integrative Medicine What is glutathione and why must we protect patient access to it?