Kidney function tests (also called renal function tests or a metabolic panel) appear on routine blood work for anyone with diabetes, high blood pressure, or a family history of kidney disease — and increasingly for general health screening. The numbers look alarming if you don't know what they represent.
Here's what the main markers actually mean.
Creatinine
Creatinine is a waste product produced by muscle metabolism. Healthy kidneys filter it efficiently out of the blood. When kidneys are working less well, creatinine accumulates and blood levels rise.
Normal ranges are roughly 60–110 µmol/L for women and 70–120 µmol/L for men, though labs vary slightly. Muscle mass affects creatinine levels — a very muscular person may run slightly high without any kidney problem. Creatinine alone is a useful signal, but it's most meaningful read alongside eGFR.
eGFR — estimated glomerular filtration rate
eGFR is the most important single number in a kidney panel. It estimates how much blood your kidneys are filtering per minute, calculated from creatinine, age, sex and sometimes ethnicity. A normal eGFR is above 60 mL/min/1.73m²; above 90 is considered healthy.
- **eGFR > 90**: normal kidney function
- **eGFR 60–89**: mildly reduced — often monitored rather than treated unless there are other concerns
- **eGFR 30–59**: moderately reduced — warrants investigation and management
- **eGFR 15–29**: severely reduced — specialist referral typical
- **eGFR < 15**: kidney failure — dialysis or transplant may be discussed
Urea (BUN in the US)
Urea is another waste product, produced when your body breaks down protein. Like creatinine, it accumulates when the kidneys aren't filtering effectively. However, urea is also affected by diet (high-protein meals raise it), hydration (dehydration concentrates it), and bleeding in the gut. A high urea with a normal creatinine often points to one of these causes rather than kidney disease.
Normal range is approximately 2.5–7.5 mmol/L (7–20 mg/dL in BUN units).
What a trend matters more than a single value
A single kidney function panel is a snapshot. What matters most to a nephrologist is the direction of travel. An eGFR of 68 is very different if it was 85 two years ago versus if it's been stable at 68–70 for a decade.
This is exactly where a longitudinal record becomes clinical useful — tracking the trend across labs from multiple providers, rather than viewing each result in isolation. Looms' lab trend view lets you plot eGFR over time so you can see immediately whether the trajectory is stable, improving, or declining.
When to speak to your doctor
Speak to your GP or internist promptly if your eGFR is below 60, if it has dropped more than 5 points since your last test, or if your creatinine has risen significantly. Don't try to interpret these results in isolation — kidney function tests are most meaningful read in the context of your full clinical picture, including blood pressure, urine protein, and symptoms.