When you begin taking a vitamin B complex supplement, your body utilizes the water-soluble micronutrients to support enzymatic reactions, red blood cell formation, and neurological health. If you previously suffered from a subclinical nutrient deficiency, correcting it often results in noticeable improvements in sustained daily energy, mental clarity, and metabolic vitality. Additionally, you may notice your urine turning a bright, fluorescent yellow-green color, which is a completely harmless, normal physiological reaction as your kidneys excrete excess riboflavin (vitamin B2).