A basic laboratory panel measuring blood urea and creatinine levels to evaluate kidney filtration capacity (eGFR). Used in the screening and follow-up of chronic kidney disease.
Indication
- Annual kidney screening in patients with hypertension and diabetes
- Evaluation of decreased urine output, edema (swelling), or uncontrolled blood pressure
- History of recurrent urinary tract infections or kidney stones
- Family history of chronic kidney disease
- Monitoring of medications excreted by the kidneys (NSAIDs, certain antibiotics, chemotherapy)
- Pre-evaluation before contrast-enhanced imaging
- Routine biochemistry before surgery
Preparation
- 8-12 hours of fasting is recommended, especially when combined with other biochemistry tests
- Avoiding excessive protein (meat) consumption in the 24-48 hours before the test is recommended
- Intense exercise can transiently raise creatinine; avoid heavy exercise the day before the test
- All medications and supplements (especially creatine supplements) should be reported to the physician
How it's performed
- About 3-5 mL of blood is drawn from a vein in the arm
- The blood is placed in a biochemistry tube and the serum is separated
- Urea (BUN) and creatinine are measured on an automated biochemistry analyzer
- eGFR (estimated glomerular filtration rate) is calculated based on age, sex, and creatinine value
- If needed, urinalysis or a 24-hour urine test may be added
Post-procedure
- Results are interpreted according to age, sex, and accompanying conditions
- The eGFR value is used to determine the stage of chronic kidney disease
- In abnormal results, urinalysis, ultrasound, or nephrology consultation may be requested
- In known kidney disease, follow-up at 3-12 month intervals is recommended
- Medication doses may be adjusted according to eGFR
Risks
- Temporary bruising at the blood draw site
- Rare hematoma formation
- Temporary lightheadedness from the needle
- Very rare local infection
FAQ
What is the normal range for creatinine?
Generally accepted limits are approximately 0.7-1.3 mg/dL in adult men and 0.6-1.1 mg/dL in women. What truly matters is not creatinine alone, but the eGFR value calculated according to age and sex.
What is eGFR and what should it be?
eGFR indicates the kidney's filtration rate. A value of 90 mL/min/1.73 m² and above is considered normal. Values below 60 persisting for more than 3 months are meaningful for diagnosing chronic kidney disease and require nephrology evaluation.
Are urea and BUN the same thing?
They are two very closely related concepts. BUN (blood urea nitrogen) is calculated from urea; some laboratories report it as BUN, others as urea. The interpretation logic is the same.
Will drinking a lot of water before the test change the result?
Severely restricted fluid intake or excessive water consumption can mildly affect creatinine. Maintaining normal fluid intake is sufficient.
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