By Jane Patel, MD — Board-certified internist with a focus on nephrology and contrast safety. Writes clinical explainers for Radcalcs.
Medically reviewed by Marcus Lee, MD (Diagnostic Radiology, 12 years) on .

What Is eGFR?

Estimated glomerular filtration rate (eGFR) is a calculated surrogate for true GFR — plasma filtered by the kidneys per minute. Direct measurement needs timed urine collections; in practice, serum creatinine is plugged into a validated equation. The current standard is CKD-EPI 2021 (race-free).

Equations normalize to 1.73 m² of body surface area, so one threshold applies across body sizes — but the result is not in absolute units. For drug dosing, use Cockcroft-Gault CrCl instead.

Key insight: eGFR answers "Does this patient fit the CKD grid?" CrCl answers "How much drug or contrast is safe now?"

What Is a Normal eGFR for Your Age?

Labs flag eGFR ≥ 60 mL/min/1.73m² as normal; above 60, kidney function is adequate at any age, and below 60 the reading warrants follow-up if persistent at 90 days.

The decline reflects physiologic nephron loss: roughly 1 mL/min/1.73m² per year after age 30–40.

Age (years)Typical eGFR range (mL/min/1.73m²)
20–29~90–120
30–39~85–115
40–49~75–105
50–59~70–100
60–69~60–95
70 and older~45–85

These are population averages for healthy adults, not pass/fail cutoffs. A 65-year-old at eGFR 55 may need monitoring; the same value in a 30-year-old needs a workup. Use the eGFR Calculator to compute CKD-EPI 2021.

CKD Stages and Their eGFR Cutoffs

KDIGO 2012 — reaffirmed in 2024 — defines six CKD stages by eGFR. Stage drives referral urgency, medication review, and imaging risk tolerance.

  • G1 — ≥ 90: damage (albuminuria, structural abnormality) required.
  • G2 — 60–89: CKD only with other evidence of damage.
  • G3a — 45–59: monitor, evaluate cause, review nephrotoxins.
  • G3b — 30–44: nephrology co-management often appropriate.
  • G4 — 15–29: prepare for renal replacement therapy.
  • G5 — < 15: kidney failure.

Most decisions cluster around G3a and G3b. Below 30, contrast becomes procedure-by-procedure and metformin is paused per FDA guidance.

Why Your eGFR Can Be Lower Than Expected

Not every low eGFR is chronic kidney disease. A single reading can move ±5 mL/min or more from reversible causes:

  • Dehydration — the most common reversible cause.
  • NSAIDs — afferent arteriolar vasoconstriction.
  • Recent ACEi / ARB start — bump up to ~30% in 1–2 weeks.
  • High-protein meal — fasting morning draws are most reliable.
  • Recent iodinated contrast — AKI may be silent for 48–72 hours.

CKD is therefore diagnosed only after eGFR < 60 persists on repeat testing more than 90 days apart.

eGFR vs. CrCl: Which One to Use When

eGFR (CKD-EPI 2021) is the metric for staging and monitoring. CrCl (Cockcroft-Gault) is in absolute mL/min — what drug-dose tables and the 5×CrCl contrast rule use. Use the CrCl Calculator for Cockcroft-Gault when drug dosing or the 5×CrCl rule is downstream. When cirrhosis and renal dysfunction intersect, the MELD Score Calculator integrates bilirubin and INR — hepatorenal physiology depresses eGFR quickly, so trend both.

A Bedside Workflow Using Radcalcs

Three steps cover most "what now?" questions once an eGFR is in front of you.

  1. Compute the eGFR. Use the eGFR Calculator with creatinine, age, and sex — confirm against the lab's report.
  2. Stage the CKD. Map to the KDIGO grid (G1–G5). Decide whether repeat testing in 90 days or nephrology referral fits the stage.
  3. Compute CrCl when dosing or contrast is on the table. Use the CrCl Calculator for Cockcroft-Gault with IBW/ABW adjustment; apply the 5×CrCl ceiling or the dose table.

The path — eGFR for staging, CrCl for dosing — keeps the right metric tied to the right decision.

Frequently Asked Questions

What is considered a normal eGFR for my age?
For most adults, eGFR ≥ 60 mL/min/1.73m² is considered normal. Above age 60, an eGFR in the 60–90 range remains age-appropriate and does not require action. Below 60 in younger adults, or below age-typical expectations in older adults, warrants repeat testing after 90 days and assessment for albuminuria or other markers of kidney damage before a CKD diagnosis can be made.
Does eGFR naturally decrease with age?
Yes — physiologically, eGFR declines roughly 1 mL/min/1.73m² per year after age 30–40, reflecting the gradual loss of functioning nephrons. An asymptomatic 75-year-old with an eGFR of 55–60 is showing age-appropriate change and should not be urgently worked up; the same value in a 35-year-old is well outside the age-typical range and warrants a full evaluation.
When should a low eGFR prompt nephrology referral?
KDIGO and most nephrology societies recommend referral for eGFR < 30 mL/min/1.73m² (stages G4 and G5), rapidly declining eGFR (a drop of >5 mL/min per year), significant albuminuria (ACR > 300 mg/g), or unexplained AKI. Earlier co-management is reasonable for any patient whose clinical picture suggests progression — diabetes with albuminuria, recurrent nephrolithiasis with obstruction, or unclear etiology after initial workup.
Can an eGFR reading be temporarily low?
Yes. Dehydration, recent NSAID exposure, ACE/ARB initiation, recent contrast, a high-protein meal before the draw, and diurnal variation can each lower a single eGFR by 5 mL/min or more. This is why CKD is diagnosed only when eGFR < 60 persists on repeat testing 90 days apart alongside other evidence of kidney damage. A single low eGFR in a stable, well-hydrated outpatient without albuminuria is usually reversible.
⚕️ Clinical Disclaimer: The information on this page is for educational purposes only. eGFR interpretation must be individualized by qualified healthcare professionals in the context of the patient's full clinical picture. Radcalcs is not responsible for clinical decisions made based on this content.

References

  1. Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int Suppl. 2013;3(1):1–150. (Updated 2024.)
  2. Levey AS, Stevens LA, Schmid CH, et al. A New Equation to Estimate Glomerular Filtration Rate. Ann Intern Med. 2009;150(9):604–612. (CKD-EPI creatinine equation, refined in 2021 race-free update.)
  3. 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(19):1737–1749.
  4. Stevens LA, Coresh J, Greene T, Levey AS. Factors Other Than Glomerular Filtration Rate Affect Serum Creatinine. J Am Soc Nephrol. 2009;20(3):552–561.
  5. U.S. Food and Drug Administration. FDA Drug Safety Communication: Metformin and Renal Function. Updated label guidance, 2016–2017.
  6. Levey AS, Inker LA. Assessment of Glomerular Filtration Rate in Health and Disease: A State of the Art Review. Clin Pharmacol Ther. 2017;102(3):405–419.