eGFR (estimated glomerular filtration rate)
Also known as: eGFR, estimated GFR, glomerular filtration rate, GFR
An estimate of how many millilitres of blood the kidneys filter each minute, calculated from creatinine together with age and sex. The number used to stage chronic kidney disease and to adjust drug doses.
- Also known as
- eGFR, estimated GFR, glomerular filtration rate, GFR
- Units
- mL/min/1.73 m²
- Measured by
- Kidney function tests, Creatinine and eGFR, Urine protein
What it is and what it does
The glomerular filtration rate is the best overall measure of kidney function but cannot be measured directly in routine care, so laboratories estimate it from serum creatinine using equations (the CKD-EPI equation in current UK and US practice; the 2021 version no longer includes a race term) that adjust for age and sex. The result is expressed per 1.73 m² of body surface area. An eGFR persistently below 60 for more than three months, or any value with markers of kidney damage such as albumin in the urine, defines chronic kidney disease, staged from G1 to G5. The estimate is least reliable at extremes of muscle mass, in pregnancy, in acute illness where creatinine is still changing, and near the normal range, where a cystatin C-based estimate can confirm the finding.
Why it may be higher
- A high value is normal in young adults and in pregnancy; falsely high estimates occur with low muscle mass (the equation assumes average muscle)
Why it may be lower
- Chronic kidney disease of any cause (diabetes, hypertension, glomerulonephritis, polycystic kidneys, obstruction)
- Acute kidney injury (the estimate lags behind the true fall because creatinine takes time to accumulate)
- Falsely low with high muscle mass, creatine supplements, a recent meat meal, or drugs that block creatinine secretion
A high or low value can be associated with several different situations. The result is interpreted with other results, symptoms, history and clinical findings.
What can affect the result
- Everything that changes creatinine independently of filtration
- Which equation the laboratory uses
- Steady-state assumption: the estimate is invalid while kidney function is changing rapidly
Medicines that can change it
Each medicine page lists its effect on this marker under "Effects on tests and results", with the source.