Serum or Plasma Creatinine Concentration (Substance Concentration)

This test gives your healthcare team important information about your health that may not show up during a routine physical exam. It can help detect problems early, guide treatment decisions, and show how well a current treatment is working, which is why your provider may recommend it for you.

Creatinine is a byproduct of muscle breakdown and is normally filtered out of your blood by your kidneys. High levels can indicate kidney problems, while low levels may suggest dehydration or other conditions. Your doctor may order this test to monitor kidney health, especially if you have risk factors like diabetes, high blood pressure, or a history of kidney disease.

Your provider will give you specific instructions before your appointment. Depending on the test, you may need to fast for a certain number of hours, avoid certain medications or supplements, or drink plenty of water. Tell your care team about all medications you take and any allergies you have.

No special preparation is usually needed, but you may be asked to fast for 8–12 hours before a blood test or to collect a 24-hour urine sample if instructed. For a blood test, you’ll have a small needle inserted into your arm. For urine, you’ll collect all urine over 24 hours in a special container. Staying hydrated can help ensure accurate results.

During the test, a trained member of your care team will follow a careful, step-by-step process to collect the information your provider needs. The procedure is usually quick and well tolerated. If any part of the test feels uncomfortable, let your care team know so they can help keep you at ease.

Blood: A small sample is taken from your arm and sent to a lab, where it’s analyzed to measure creatinine levels. Urine: A 24-hour urine collection is sent to the lab for testing. The lab uses specialized equipment to detect and quantify creatinine, often through methods like enzymatic or nephelometric analysis.

Your healthcare provider will explain your results, usually within a few days. Results within the expected range are considered normal, while results outside that range do not always mean something is wrong. Your provider will review them alongside your overall health and may recommend follow-up testing if needed.

Results are compared to a general reference range (not provided here) to determine if your levels are normal or if further evaluation is needed. High creatinine levels may signal impaired kidney function, while very low levels could indicate dehydration or muscle breakdown. Your doctor will discuss results in the context of your overall health.