Just above a litre of blood passes both kidneys every minute and one tenth gets filtered out as fluid. Blood cells, most proteins and fat particles stay in. Water and anything smaller get squeezed out!
Next, the kidneys do some fine tuning. They take back in what is useful to the body: the right amount of minerals, glucose, amino-acids and water.
3 Water balance.
Kidneys pee more when we drink more but conserves water by peeing little if we are not drinking enough.
Hundreds of waste products like urea, toxins and drugs are filtered out and not taken back. This way, the kidneys keep the inside of the body clean.
5 Acid-base balance
Our bodily functions like food metabolism produce a lot of acid. The kidneys are the only organs that gets rid of excess acid.
The kidneys keep the environment in the body stable. It includes keeping the concentration of many chemicals in the body within a tight range.
7 Blood pressure control.
The kidneys control blood pressure by getting rid of excess salt and releasing various hormones. If the kidneys are diseased, blood pressure goes up.
8 Erythropoeitin production
The kidneys produce erythropoeitin (EPO) that makes the bone marrow produce red cells. Without any EPO, we become severely anaemic.
9 Vitamin D activation
Kidneys convert the vitamin D we get from food and the sun into an active form that keep our bones strong and healthy.
10 Glucose control
The kidneys help to stabilise blood sugars by controlling the loss of glucose in the urine and by making new glucose when levels go low. This is why the newest class of drugs for diabetes act on the kidneys.