The kidney is responsible for filtering this from the blood and discarding it in the urine. Another product, called Creatinine, is produced by the day to day build up and break down of muscles. Because the production is fairly constant, the Creatinine level in your blood is usually used as an indicator of how well your kidneys are functioning. Your kidneys regulate many of the elements in the body such as sodium, phosphorus, and potassium. Phosphorous is important, along with calcium, in keeping your bones strong.
Potassium is one of the most important elements in the body.
It is also in the food we eat. It is important to have the proper levels in the body, as either too high or too low a level of potassium can cause serious, life-threatening problems, usually without symptoms. Normally functioning kidneys will keep these elements in the right range. It is the kidney that controls the amount of fluid in the body and, most importantly, fluid that is in the bloodstream. One day you may drink a lot of water, and then another day you may not.