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Serum Creatinine with Glomerular Filtration Rate (GFR) Estimation (using a modified equation)

Published: August 9, 2026Updated: August 16, 2026

This test measures your kidney function by checking how well your kidneys filter waste products from your blood, using creatinine levels and a formula to estimate your glomerular filtration rate (GFR).

Quick summary

["Your kidneys filter waste from your blood; this test helps assess how well they’re working."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
27368-0
Short code
C trach B Ab Titr Ser IF
Synonyms
C trach B Ab Titr Ser IF
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What Does This Test Measure?

Creatinine is a waste product from muscle metabolism that kidneys normally filter out of your blood. The test measures your serum creatinine level and uses it along with other factors (like age, sex, and race) to estimate how much blood your kidneys filter each minute (GFR). GFR is a key indicator of kidney function—lower values may suggest kidney damage or disease.

Why Is This Test Done?

Doctors order this test to monitor kidney health, especially if you have conditions like diabetes, high blood pressure, or a family history of kidney disease. It helps track how well your kidneys are working over time and can signal early signs of kidney problems.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the test if it’s part of a metabolic panel. Bring your recent medications to discuss with your provider.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm. The process takes a few minutes, and you may feel a brief pinch. The blood is sent to a lab for analysis.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Creatinine GFR

Frequently asked questions

How often should I get this test?
Your doctor will determine how often you need this test based on your health history, symptoms, and risk factors. For example, people with diabetes or kidney disease may need it more frequently than others.
What are the typical reference ranges for this test?
Reference ranges vary by lab and individual factors like age, sex, and muscle mass. Your doctor will provide your specific results and compare them to your baseline or clinical needs.
Can diet or medications affect this test?
Yes, high-protein diets or certain medications (like NSAIDs) can temporarily raise creatinine levels. Your doctor may adjust your diet or medications if needed, especially if you have kidney concerns.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy