Kidney health · 6 min read
Creatinine to eGFR — how the number is made.
There's no simple "creatinine × something = eGFR" conversion. Your eGFR comes from an equation — the CKD-EPI 2021 formula — that takes your serum creatinine plus your age and sex. That's why the same creatinine gives a different eGFR for a young adult and an older one. Here's what the blood test measures and how it becomes the kidney number on your report.
Last updated April 15, 2026.
What creatinine actually is
Creatinine is a waste product your muscles make at a fairly steady rate. Healthy kidneys filter it out of the blood into the urine, so the amount left in your blood reflects how well the kidneys are filtering. When filtration falls, creatinine rises. On its own, though, a creatinine value is hard to interpret — which is why labs convert it into eGFR.
Why age and sex are in the equation
Muscle mass shapes how much creatinine you produce, and it tends to differ with age and sex. The CKD-EPI 2021 equation accounts for this so the estimate reflects kidney function rather than body build. Notably, the 2021 version removed the older race coefficient — it uses creatinine, age, and sex only, and is the standard now endorsed by the National Kidney Foundation and the American Society of Nephrology.
That's also why you can't eyeball eGFR from creatinine: a creatinine of 1.2 mg/dL might be a normal eGFR in a young man but a reduced eGFR in an older woman. The equation does the weighting for you — a calculator is the practical way to apply it.
mg/dL vs µmol/L — the units
Creatinine is reported in mg/dL in the US and in µmol/L across the UK, Europe, and much of the world. To convert: mg/dL × 88.42 = µmol/L, and µmol/L ÷ 88.42 = mg/dL. So 1.0 mg/dL ≈ 88.4 µmol/L. A good eGFR calculator lets you enter either unit — just make sure the unit you pick matches your lab report.
Where creatinine-based eGFR falls short
Because creatinine comes from muscle, the estimate can mislead when muscle mass is unusual. It may read falsely low in very muscular people or bodybuilders, and falsely high in people with low muscle mass, amputations, or malnutrition. Pregnancy, certain medications, and a recent high-protein or creatine-supplemented diet can also shift creatinine. When accuracy matters, clinicians may add a cystatin C-based estimate, which doesn't depend on muscle in the same way.
Frequently asked questions
Is there a simple formula to convert creatinine to eGFR?+
Not a one-to-one conversion. eGFR is calculated from serum creatinine using an equation — the CKD-EPI 2021 formula — that also needs your age and sex. The same creatinine value gives a different eGFR for a 30-year-old versus a 70-year-old, so you can't read eGFR off creatinine alone. Use a calculator that implements the equation.
What is a normal creatinine level?+
Roughly 0.7–1.3 mg/dL (about 62–115 µmol/L) for men and 0.6–1.1 mg/dL (about 53–97 µmol/L) for women, but reference ranges vary by lab and by muscle mass. Because normal ranges are broad, clinicians rely on the eGFR derived from creatinine rather than the raw creatinine value alone.
How do I convert creatinine between mg/dL and µmol/L?+
Multiply mg/dL by 88.42 to get µmol/L; divide µmol/L by 88.42 to get mg/dL. For example, 1.0 mg/dL equals about 88.4 µmol/L. US labs typically report mg/dL, while the UK, Europe, and many other regions use µmol/L.
Why does muscle mass affect the result?+
Creatinine is a waste product of muscle metabolism, so people with more muscle produce more of it and those with very little muscle produce less. This means creatinine-based eGFR can read falsely low in very muscular people and falsely high in those with low muscle mass. In those cases a cystatin C-based estimate may be more accurate.
Enter your creatinine (mg/dL or µmol/L), age, and sex to get your eGFR with the CKD-EPI 2021 equation.
For general education only. Not medical advice or a diagnosis. Discuss your results with a qualified healthcare professional. References: Inker LA, Eneanya ND, Coresh J, et al. New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race. N Engl J Med. 2021;385:1737-1749; National Kidney Foundation.