This is a test in which the blood samples are checked for the amounts of certain substances released by the kidneys. Normally we do not feel any discomfort when our kidneys are not functioning well. Through the blood test, we can actually know how healthy our kidneys. The renal function test includes sodium, potassium, chloride, urea, creatinine, calcium, phosphate and uric acid.

- Sodium, chloride: It is regulated by the kidneys. Foods we eat contain sodium chloride (salt). Too much sodium is harmful for us with kidney disease. Sodium helps our body to maintain a healthy fluid balance. But having renal disease means our kidneys cannot eliminate excess sodium and fluid from your body. So sodium and fluid build up in our bloodstream, causing high blood pressure.

- Potassium: Potassium is a mineral found naturally in many fruits and vegetables. Healthy kidneys measure potassium in our blood and remove excess amounts. People who have disease kidneys may fail to remove excess amount of potassium, and with very poor kidney function. High potassium levels can affect the heart rhythm.

- Creatinine: Creatinine is a waste product in the blood created by the normal breakdown of muscle cells during metabolism. Healthy kidneys take creatinine out of the blood and put it into the urine to leave the body. When kidneys are not working well, creatinine builds up in the blood. Slightly increases in creatine level can appear after meals, especially after ingestion of large quantities of meat.

- Calcium and phosphate: Calcium is a mineral that is found throughout our body. It makes up together with phosphate. The blood calcium level need to keep very tightly controlled for the body to work normally. Both minerals are too high or too low will cause kidney failure or other diseases such as osteoporosis.

- Uric Acid: It is water insoluble end product of purine nucleotide metabolism. Food such as meat, beans, internal organs of animal and seafood will increase the level of uric acid. The higher level of uric acid deposition in kidneys will cause gout.