Short answer: Creatinine is a waste product of muscle that the kidneys remove from the blood; the blood test measures how much is there. eGFR (estimated glomerular filtration rate) is not measured: it is calculated from creatinine, age and sex to estimate how much blood the kidneys filter each minute. Together they are the standard way kidney function is reported.
At a glance
| Creatinine | A waste product of muscle the kidneys remove; measured |
|---|---|
| eGFR | Calculated from creatinine, age and sex; an estimate of filtration |
| Units | mg/dL or µmol/L for creatinine; mL/min/1.73 m² for eGFR |
| LOINC | 2160-0 (creatinine), 62238-1 (eGFR CKD-EPI) |
| Moves with | Muscle mass, hydration, meat intake, some medicines |
| Keep | Both values with the date; kidney function is read as a trend |
What the test measures
Muscle produces creatinine at a fairly steady rate, and healthy kidneys filter it out. When filtering slows, creatinine rises and eGFR falls. eGFR is reported in mL/min/1.73 m², which adjusts for body size.
Labs use formulas such as CKD-EPI (the 2021 version no longer uses race). Creatinine also depends on muscle mass, so very muscular or very thin people, children and pregnant women need careful interpretation; cystatin C is another marker doctors may add.
When it is ordered
Common reasons, which your doctor adapts to you:
- as part of a routine metabolic panel;
- in people with diabetes, high blood pressure or heart disease;
- before and during medicines that affect or depend on the kidneys.
How the result is written on the report
| Result on the report | LOINC code | Usual unit | Also seen as |
|---|---|---|---|
| Creatinine, serum or plasma | 2160-0 | mg/dL | µmol/L (×88.4) |
| eGFR, CKD-EPI 2021 | 98979-8 | mL/min/1.73 m² | — |
| eGFR, CKD-EPI (earlier) | 62238-1 | mL/min/1.73 m² | — |
| Urea nitrogen (BUN) | 3094-0 | mg/dL | mmol/L urea (×0.357) |
µmol/L = mg/dL × 88.4: 1.0 mg/dL ≈ 88 µmol/L. eGFR uses the same unit everywhere. BUN in mg/dL becomes urea in mmol/L with a factor of 0.357.
Reading your report
International guidelines (KDIGO) use an eGFR below 60, or signs of kidney damage such as albumin in the urine, lasting more than three months as part of the definition of chronic kidney disease; a single low value can be temporary (dehydration, a recent large meat meal, intense exercise, some medicines). Doctors read eGFR together with the urine albumin-to-creatinine ratio. Note which formula your lab uses when comparing results over years.
Keeping the results in your record
Scan or photograph the report in Anpheros Daily: each value is read with its unit and the laboratory's reference range, you check it, and it is stored with its LOINC code as an HL7 FHIR Observation, a format used by many hospitals and national health systems. Results from different laboratories line up on one chart over time, and the lab unit converter helps when two reports use different units. Our guide on how to read lab results explains reference ranges and flags in general; the lab results guide for a new doctor shows how to share them.
What this page does not do
It explains what the test is and how the result is written. It does not interpret your result, diagnose or recommend treatment: the meaning of a value depends on your history, your other results and how the sample was taken, and that is your doctor's job.
Related pages
- Urine albumin-to-creatinine ratio (ACR, microalbumin)
- Basic vs comprehensive metabolic panel (BMP and CMP)
- Uric acid blood test
Sources
Frequently asked questions
Is eGFR measured or calculated?
Calculated, from your creatinine, age and sex, with a formula such as CKD-EPI 2021.
How do I convert creatinine from mg/dL to µmol/L?
Multiply by 88.4. For example, 0.9 mg/dL is about 80 µmol/L.
Can exercise or diet change my creatinine?
Yes. Intense exercise, dehydration and a large meat meal shortly before the test can raise it temporarily.
Why did my eGFR change when the lab changed formula?
Different formulas give slightly different results. Compare results calculated the same way, or ask the lab which formula it uses.
Try it in Anpheros Daily
Photograph your lab report and Anpheros Daily lines up each value with its reference range, so you can compare reports from different laboratories.
How it works in the app →
Anpheros builds a medical record that the patient controls and can share with any clinic, on an HL7 FHIR R4 platform, based in the EU. These guides help you understand and organise your health; they do not replace your doctor.
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