The kidneys make urine when they filter your blood. Water makes up 95% of urine. The other 5% consists of materials such as creatinine, urea, ammonia and the ions of sodium, calcium and potassium. This ratio is noteworthy because too much or too little water, plus other factors, affect the color of your urine. What are the different colors of the urine? What do they mean? When should I see my doctor?