Serum or Plasma Creatinine Concentration (Mass Concentration)

Why Your Kidneys Matter

Creatinine is produced when your muscles break down proteins. Normally, your kidneys filter it out of your blood and remove it from your body through urine. If your kidneys aren’t working well, creatinine builds up in your blood, which can indicate kidney problems.

What the Test Tells Us

This test helps doctors check how well your kidneys are working. It’s often used alongside other tests, like urine tests, to diagnose and monitor kidney disease. It can also help determine how severe kidney problems are and whether treatment is needed.

How the Test Is Done

A small blood sample is taken from a vein, usually in your arm. The sample is sent to a lab where it’s analyzed to measure creatinine levels. Sometimes, a 24-hour urine sample is collected to measure creatinine clearance, which gives a different but related measure of kidney function.

What to Expect Before the Test

There are usually no special preparations needed for this blood test. If you’re having a 24-hour urine test, you’ll need to collect all urine for a full day, starting right after you wake up and ending just before you go to bed the next day. Drink plenty of water to help your kidneys work normally during this time.