A kidney function panel can look like a wall of numbers. This guide explains how to read the two values that carry the most weight, eGFR and the stage it maps to, and why serum creatinine has no single universal cut-off. It is a reading guide, not a diagnosis.
This article is educational and does not replace clinical training or advice for a specific patient. All clinical decisions rest with the treating clinician.
What kidney function tests measure
The headline number on most reports is the estimated glomerular filtration rate, or eGFR. eGFR is estimated from serum creatinine together with age, sex, and body size. (NCBI Bookshelf) It approximates how well the kidneys filter blood, which is why it is read before any single raw lab value.
Chronic kidney disease, or CKD, is the condition these tests screen for. Chronic kidney disease is defined as kidney damage or an eGFR under 60 mL/min/1.73 m2 persisting for 3 months or more. (NCBI Bookshelf) The word chronic matters, because a single result does not meet that standard on its own.
How to read a kidney function report step by step
1. Locate the eGFR first
Find the eGFR value before anything else. Because eGFR is estimated from serum creatinine together with age, sex, and body size, the same creatinine can produce different eGFR values in different people. (NCBI Bookshelf)
2. Compare eGFR against the normal range
Normal GFR or eGFR is 90 to 125 mL/min in adults older than 2, and for an adult male it is 90 to 120 mL/min. (NCBI Bookshelf) Reference ranges vary by laboratory, so read the value against the range printed on your own report rather than a number from memory.
3. Read creatinine in context, not as a fixed number
Serum creatinine reference intervals depend on age and sex, and the source does not give a single fixed creatinine number. (NCBI Bookshelf) Treat creatinine as a value to compare against the interval your laboratory prints, not one universal cut-off.
4. Map eGFR to a CKD stage
The KDIGO GFR stages, in mL/min/1.73 m2, are stage 1 over 90, stage 2 is 60 to 89, stage 3a is 45 to 59, stage 3b is 30 to 44, stage 4 is 15 to 29, and stage 5 under 15. (NCBI Bookshelf)
5. Check persistence before calling it chronic
Per the standard criteria, chronic kidney disease is defined as kidney damage or an eGFR under 60 mL/min/1.73 m2 persisting for 3 months or more. (NCBI Bookshelf) One low reading is not the same as a diagnosis, which is made by a clinician.
Normal values and CKD stages at a glance
| Measure | Value | Source |
|---|---|---|
| Normal GFR or eGFR, adults older than 2 | 90 to 125 mL/min | (NCBI Bookshelf) |
| Normal eGFR, adult male | 90 to 120 mL/min | (NCBI Bookshelf) |
| CKD stage 1 | over 90 mL/min/1.73 m2 | (NCBI Bookshelf) |
| CKD stage 2 | 60 to 89 mL/min/1.73 m2 | (NCBI Bookshelf) |
| CKD stage 3a | 45 to 59 mL/min/1.73 m2 | (NCBI Bookshelf) |
| CKD stage 3b | 30 to 44 mL/min/1.73 m2 | (NCBI Bookshelf) |
| CKD stage 4 | 15 to 29 mL/min/1.73 m2 | (NCBI Bookshelf) |
| CKD stage 5 | under 15 mL/min/1.73 m2 | (NCBI Bookshelf) |
| Serum creatinine | Varies by age and sex, no single fixed value | (NCBI Bookshelf) |
Reference ranges vary by laboratory, so always compare a result against the range on your own report.
Common mistakes when reading these tests
- Reading creatinine as one universal number. Serum creatinine reference intervals depend on age and sex. (NCBI Bookshelf)
- Calling a single low eGFR “CKD.” The standard criteria require the finding to persist for 3 months or more. (NCBI Bookshelf)
- Forgetting laboratory variation. Reference ranges vary by laboratory, which is why the printed range on your own report is the one that counts.
- Confusing the estimate with a direct measurement. eGFR is estimated from serum creatinine together with age, sex, and body size. (NCBI Bookshelf)
When to see a clinician
Interpretation and diagnosis belong to a clinician. If your eGFR falls below the normal range, if a report flags values as abnormal, or if you are unsure what a result means, discuss it with the treating clinician. A chronic kidney disease diagnosis is made against the standard criteria per (NCBI Bookshelf), not from a single number you read at home.
How Phở Labs handles this
Phở Labs publishes cited explainers like this one. Every factual claim here is linked to the source it came from, and where a source does not give a fixed value, such as a single normal creatinine number, we say so rather than guess. That cite-or-abstain approach is the point, so you can check each statement against the reference behind it.
References
- Glomerular filtration rate and CKD staging: https://www.ncbi.nlm.nih.gov/books/NBK507821/
- Chronic kidney disease definition: https://www.ncbi.nlm.nih.gov/books/NBK535404/