What is eGFR? Why the trend matters more than one result
eGFR estimates kidney filtration. A drop over two years carries information a single in-range value cannot.
Key takeaways
- eGFR estimates kidney filtration from a blood test, so the change between results carries information a single value cannot.
- In 1.7 million adults, a fall of 30% or more over two years happened to about 7 in 100 people, far more often than a doubling of creatinine.
- That smaller drop was strongly and consistently linked to later kidney failure and, less steeply, to death.
- The 2024 KDIGO guideline gives cystatin C more weight alongside creatinine and moves toward individualized risk.
eGFR estimates how well your kidneys filter, from a blood test.
In 1.7 million adults across 35 cohorts, a fall of 30% or more over two years was far more common than a doubling of creatinine and was strongly linked to later kidney failure.
The 2024 KDIGO guideline puts more weight on cystatin C alongside creatinine, and on individualized risk.
What is eGFR?
eGFR stands for estimated glomerular filtration rate. It is calculated from a blood marker, usually creatinine, and estimates how much blood your kidneys filter each minute. Most people see it on a routine metabolic panel, usually flagged only when it falls below the lab range.
Why one value undersells it
Kidney research has long used a doubling of serum creatinine, which corresponds to roughly a 57% fall in eGFR, as its marker of progression. The CKD Prognosis Consortium describes that as a late event.
Their pooled analysis of 1.7 million participants from 35 cohorts looked at smaller changes over one to three years. A drop of 30% or more over two years affected about 6.9% of participants, against 0.79% for the doubling. And the smaller drop was strongly and consistently associated with later kidney failure and with mortality.
What the numbers looked like
For people already starting near an eGFR of 35, which is in the kidney disease range, the average 10-year risk of kidney failure was 64% after a 30% drop, compared with 18% with no change. Mortality followed a similar but weaker pattern. These figures are for people with reduced kidney function to begin with, not for the general population.
Cystatin C and the 2024 KDIGO guideline
The Kidney Disease: Improving Global Outcomes (KDIGO) 2024 guideline places greater emphasis on cystatin C for assessing filtration, and shifts toward an individualized, risk-based approach to predicting kidney failure.
How Baseline reads it
We look at eGFR as a series, not a snapshot. Where you choose to test, lining up results year over year shows whether the direction is stable, and pairing creatinine with cystatin C gives a second view when the picture is unclear.
What this means for you
An in-range eGFR is one data point. Ask to see your results side by side over the years, and look at the direction.
Common questions
What is eGFR?
eGFR stands for estimated glomerular filtration rate. It is calculated from a blood marker, usually creatinine, and estimates how much blood your kidneys filter each minute.
Does a small drop in eGFR matter if it is still normal?
Direction carries information. In a pooled analysis of 1.7 million adults, a 30% fall over two years was strongly linked to later kidney failure, even though it is far smaller than the changes traditionally used to define progression.
What is the difference between creatinine and cystatin C?
Both are blood markers used to estimate filtration. The 2024 KDIGO guideline puts greater emphasis on cystatin C for assessing filtration, alongside creatinine.
References
- Coresh et al., decline in estimated glomerular filtration rate and subsequent risk of end-stage renal disease and mortality, CKD Prognosis Consortium, JAMA, 2014
- Madero et al., evaluation and management of chronic kidney disease, synopsis of the KDIGO 2024 clinical practice guideline, Annals of Internal Medicine, 2025
- Biomarker hub: Metabolic biomarkers