Why Your Pee Turns Bright Yellow from Certain Supplements Glutathione You Are The Healer 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 Pee Bright Yellow? Yellow Urine Causes & Symptoms 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 First time taking a multivitamin. Urine is neon yellow and it's freaking me out : r Supplements