How to Check Your Kidneys With Blood Work

Kidneys act as filters for the blood, funneling waste products from the blood to the bladder in a complex process. They also manage the levels of important substances in the body and release hormones that regulate blood pressure. Your doctor may order blood tests to see if your kidneys are functioning properly. If your kidneys are not able to filter as they should, the levels of certain types of waste products in your blood will be high.

Instructions

Checking for Kidney Trouble

• 1

  Blood pressure and urine tests are quick clues to kidney function.

  Start with the less invasive tests. Most doctors will measure blood pressure and test urine first. Elevated blood pressure can provide a clue about kidney function. Most doctor visits include a simple measurement of blood pressure--make sure this gets recorded. Next, the doctor may take a urine sample and test it for proteins. Healthy kidneys filter out wastes but leave proteins in the body, so if the kidneys are dumping proteins into the urine, this is a sign of a kidney problem.

• 2

  Getting blood drawn takes little time, but you may need to fast first.

  If your doctor gives you a lab slip for a blood test, call the lab to verify that it accepts your insurance and to see if you need to make an appointment. You will probably need to fast for eight hours before the blood is drawn, so plan a morning visit to the lab. The phlebotomist will take a vial or two of blood and you will be on your way. The doctor's office will call you with results a few days later. If your results are normal, you may receive a letter instead.

• 3

  A lab will test for above-normal levels of creatinine in blood.

  Understand the blood test results. The most common test is a creatinine test. Creatinine is produced in the body whenever muscles are used, and it ends up in the blood as waste. Healthy kidneys filter it out, so a blood test should show low levels of creatinine in the blood. "Normal" ranges of creatinine in the blood vary, depending on how much muscle mass a person has. A result of two to four mg/dL indicates that the kidneys are not functioning properly.

• 4

  If you eat a lot of protein, your BUN levels may be slightly elevated.

  Another test your doctor may order is the Blood Urea Nitrogen (BUN) test. Urea nitrogen is a waste product in your blood from the breakdown of proteins you have eaten. Urea nitrogen is normally removed by your kidneys, but if they are failing to do their job, BUN levels will be high in your blood. BUN could be on the high end if you eat a lot of protein, so it's helpful for the doctor to have this test result alongside the numbers from your blood creatine and urine protein tests.