2. Blood Tests (also called as Kidney function tests):

Blood Urea Nitrogen (BUN) Blood carries protein to cells throughout the body. After the cells use the protein, the remaining waste product is returned to the blood as urea, a compound that contains nitrogen. Healthy kidneys take urea out of the blood and put it in the urine. If your kidneys are not working well, the urea will stay in the blood. A deciliter of normal blood contains 7 to 20 milligrams of urea. If your BUN is more than 20 mg/dL, your kidneys may not be working at full strength. Other possible causes of an elevated BUN include dehydration and heart failure.

Serum Creatinine: A nitrogenous waste product formed in the muscle and excreted by the kidney. When kidneys are diseased, creatinine is retained in the blood so its level rises.

3. Urine Test:
Healthy kineys filters mainly waste (urea, creatinine) from the blood , not proteins, blood cells etc. When kidney is diseased it starts filtering initialy small amounts of protein (albumin) called as Microalbuminuria and later large amount of protein caleed as Proteinuria.

Microalbuminuria and Proteinuria: Healthy kidneys take wastes out of the blood but leave protein. Impaired kidneys may fail to separate a blood protein called albumin from the wastes and albumin may leak into the urine, a condition known as Microalbuminuria, a sign of deteriorating kidney function. As kidney function worsens, the amount of albumin and other proteins in the urine increases and the condition is called Proteinuria.