Serum or Plasma Creatinine Concentration (Mass Concentration)

Why Your Kidneys Matter

Your kidneys filter waste and extra fluids from your blood to keep your body balanced. Creatinine is a byproduct of muscle metabolism that your kidneys remove. If your kidneys aren’t working well, creatinine levels can build up in your blood, which your doctor can spot with this test.

What Causes Creatinine Levels to Change?

Several factors can affect creatinine levels, including muscle mass (more muscle means more creatinine), dehydration, diet (high-protein foods), or kidney disease. If you’ve had recent surgery, illness, or changes in fluid intake, those can also impact results.

What Does a High or Low Level Mean?

High creatinine levels may signal kidney problems, though other conditions (like dehydration or muscle injury) can also cause them. Low levels might suggest kidney function is better than usual, but they can also be due to factors like low muscle mass or certain medications.

When You Might Need This Test

Doctors often order creatinine tests to check kidney health before surgeries, during pregnancy, or if you have symptoms like swelling, fatigue, or changes in urine. It’s also part of routine check-ups for people with diabetes or high blood pressure.